Saturday, February 9, 2013

The first batch of Mansoura Manchester programme.......The future doctors and Dr. Alaa Mosbah in this pic

Congratulations, graduate( 2013).
May your new path take you where you want to go
and also bring you pleasant surprises

Thursday, January 24, 2013

Laparoscopic RT.salpingo-oophrectomy for large ovarian tumor in child aged 10 years done by Dr. Alaa Mosbah

Laparoscopic RT. salpingo-oophrectomy for large ovarian tumor
DR.Alaa Mosbah

سبق لجامعة المنصورة استئصال ورم لطفلة 10سنوات بالمنظار‎

الخميس 24 يناير 2013   4:05:10 م
البشاير ـ ريم حبيب :

فى سبق متميز لقسم امراض النساء والتوليد بجامعة المنصوره قام الاستاذ الدكتور علاء مصباح وفريق طبى برئاسة الدكتورعلاءمصباح و الدكتوره ساره عبد العزيز والدكتوره هبه نجيب . باجراء عملية ازالة ورم بالمبيض الايمن والانبوب الايمن بالمنظار الجراحى لطفله فى العاشره من عمرها لم تتم سن البلوغ

ويقول الدكتور علاء مصباح : ان هذه اول عمليه فى جامعة المنصوره باستخدام المنظارالجراحى وذلك للحفاظ على الخصوبه فى المستقبل ومنعا لحدوث التصاقات بلحوض وتقليل مضاعافات بعد العمليه وعدم ترك اثر لجرح كبير فى البطن والعوده سريعا للحياه الطبيعيه فى خلال ساعات

وان يتم استئصال ورم 10 سم فى 10 سم من خلال المنظار مع صغرحجم البطن وصغر سن المريضه فكان عمل شاق جدا وتقول الحاجه سعاد رشاد جدة الطفله والمرافقه لها المريضه اسمها ساره محمد محمود اليمانى فى الخامس الابتدائى بدائت معاناتها منذ سنتين حيث انتابها مغص حاد وذهبنا بها الى دكتورفى المحله الكبرى حيث محل سكننا فظنوا انه التهاب حاد فى الذائده وبعد الاشعات تبين انه تكيس على المبيض

وقال انه لا يستطيع ان يوصى بجراحه وظلت لمدة عامين تتعايش على المسكنات وسائت حالتها اكثر ذهبنا لمستشفى اطفال المنصوره وبعد الاشعات حولونا الى قسم النساء والتوليد فى مستشفى الجامعه واتضح ان هناك ورم كبير على المبيض وقام الاطباء بعمل الجراحه لها وهى فى طريقها للتعافى وتقول ساره ان بشكر ا لدكتورعلاء علشان خلانى اخف من الوجع الى كان عندى علشان اعرف ارجع المدرسه لانى نفسى اكبر ابقى مدرسه

Friday, April 22, 2011

Bacterial Infections and Pregnancy

Bacterial Infections and Pregnancy


Fetal and Newborn Infections

-In utero (transplacentally) ,congenital syphilis

-During labor (vertical transmission) , E. coli, group B streptococci, ;conjunctivitis due to chlamydia, gonorrhea or Listeria monocytogenes, and a number of infections due to gram-negative anaerobic bacilli.

-In the neonatal period (i.e., during the first 28 days following birth) , tuberculosis and tetanus

Group B Streptococcus (GBS)

Clinical spectrum

Because only 0.5-1% of mothers who carry GBS develop signs and symptoms of disease, clinical diagnosis of GBS can be problematic.

In pregnant women, GBS is a cause of cystitis, amnionitis, endometritis, and stillbirth. Occasionally, GBS has been a cause of endocarditis and meningitis, while in postpartum women, it has been identified as a cause of urinary tract infections (UTIs) and pelvic abscesses.
Prenatal screening for this condition is now established practice in North America, Australasia and many parts of Europe
The UK and Finland stand out as the only two countries to have consciously resisted this trend, and this is, at least in part, because the incidence of early onset neonatal infection in the UK is less than a third of what it was in America

Group B Streptococcus – background

Streptococcus agalactiae:

Group B Strep, Strep B, beta haemolytic Strep, GBS


Intestinal (up to 30% of adults) & vaginal (up to 25% of women)


May be intermittent

90% of adults possess no protective antibodies to GBS


Infections in adults: the elderly, pregnant women, others with other disease

Most common cause of life-threatening infection in newborn babies

Underlying rate ~ 1/1000 live births overall

GBS infection in babies

Early Onset

Up to 80% of GBS infection in babies

0-6 days (usually less than 24 hours)

Usually septicaemia, also meningitis & pneumonia

11% die

Late onset

Up to 20% of GBS infection in babies
Start 7 or more days after delivery
Usually septicaemia, and meningitis
5% die

Reducing risk of GBS infection in babies

Late onset GBS infection

No medical intervention proven to prevent

Good hygiene

Education / alert

In future – vaccination of women before/during pregnancy

Will prevent EO/LO and adult GBS infection
Reducing risk of GBS infection in babies

Early onset GBS infection

-Intrapartum antibiotic prophylaxis (IAP)

Only proven effective method of prevention available

-Oral antibiotics

No evidence it reduces EOGBS infection

Used to treat GBS in urine

-Intramuscular antibiotics before labour

May eradicate GBS colonisation for up to 6 weeks

-Vaginal flushing with chlorhexidine

No evidence it reduces EOGBS infection

Recognised risk factors for EOGBS infection

Previous baby with GBS infection x 10

GBS bacteriuria during pregnancy x 4

Intrapartum fever x 3

Preterm labour x 3

Prolonged rupture of membranes x 3

Maternal GBS colonisation during pregnancy x 4

But … there’s no way to know a woman is carrying GBS unless we look for it

Testing for GBS carriage

When to swab?

Before 35 weeks of pregnancy

35-37 weeks of pregnancy

Where to swab? (not speculum)

-High vaginal swab

-Low vaginal swab

-Low vagina & anorectal swab/s (more than 30% more effective than vaginal or cervical alone)

Who to swab?
Pregnant woman

What culture method to use?

Direct agar plate - 24-48 hours to grow culture in lab

Selective Enriched Culture Medium (ECM) - 24-48 hours to grow culture in lab

Polymerase Chain Reaction (PCR) – minutes to hours to grow culture

PCR requires special equipment and special training

Who should be offered intrapartum antibiotic prophylaxis?

-Women with recognised risk factors:

50-60% cases prevented

-GBS carriers this pregnancy:

80-90% cases prevented

-GBS carriers this pregnancy who have risk factors:

less than 50% cases prevented

UK – RCOG guideline summary


Routine screening for GBS not recommended

Antenatal treatment with penicillin is not recommended


Clinicians should discuss the use of IAP in the presence of known risk factors including incidental carriage.

Risk factors include:

Prematurity less than  37 weeks

prolonged rupture of membranes more than 18 hours

fever in labour more than 38C

The argument for prophylaxis becomes stronger for mor than 2 risk factors.

IAP should be considered if GBS is detected incidentally in the vagina or the urine in the current pregnancy

IAP offered to women with a previous baby with neonatal GBS disease.

IAP regime is Penicillin G as soon as possible after the onset of labour and at least 2 hours before delivery.

If chorioamnionitis is suspected, broad-spectrum antibiotic therapy including an agent active against GBS should replace GBS-specific antibiotic prophylaxis

Mother should receive antibiotics

mother should receive antibiotics using the following criteria:

Previously delivered infant with invasive GBS infection

GBS bacteriuria during current pregnancy

Delivery at less than 37 weeks' gestation

Duration of ruptured membranes longer than 18 hours

Intrapartum temperature of more than 100.4°F (38°C)

During labor, 5 million U of penicillin G should be given as an intravenous loading dose, followed by 12-24 million U/d in 4 divided doses.

An alternative therapy is 2 g of ampicillin as an intravenous loading dose, followed by 1 g every 4 hours until delivery.

In case of penicillin allergy, clindamycin 900 mg IV every 8 hours until delivery or erythromycin 500 mg IV every 6 hours until delivery may be given.

Neonates delivered from a mother who received prophylaxis require careful observation for signs and symptoms of disease.


Women are predisposed to UTIs compared with men because of :

their anatomically shorter urethra,

the proximity of the urethra to the well-colonized anus and vagina, and

trauma during sexual intercourse.

UTIs are an especially important topic in pregnancy because even asymptomatic bacteruria can lead to complications such as pyelonephritis and premature labor.


The most common causative organisms are as follows:

Escherichia coli

Klebsiella species

Enterobacter species

Enterococcus species

Group B Streptococcus

Staphylococcus saprophyticus

Proteus mirabilis

Pseudomonas aeruginosa

Citrobacter diversus

Clinical spectrum

Infection can involve the lower and upper urinary tracts, and patients can present with asymptomatic bacteriuria, cystitis, or pyelonephritis.

Bacteriuria that does not manifest symptoms apparently does not occur more frequently with pregnancy but is more likely to result in acute pyelonephritis in pregnant women.

Approximately 28% of pregnant women with untreated bacteriuria develop pyelonephritis. Some of the complications of bacteriuria observed in pregnancy include maternal anemia, low neonatal birth weight, hypertension, and prematurity.

Cystitis does not occur more frequently in pregnant women. The symptoms of cystitis are often confused with symptoms noted in normal pregnancy. These findings include urgency, frequency, suprapubic discomfort, and dysuria without fever or costovertebral angle tenderness. Urine culture findings are positive, and urinalysis reveals occasional hematuria or pyuria.

Acute pyelonephritis occurs with increased frequency in pregnant women (rate of 1-2%) and is most likely due to stasis of urine and bacteria in the urinary tract because of relative obstruction. This is caused by the dilatation of the ureters secondary to progesterone in early pregnancy and to the mechanical obstruction from the gravid uterus later in pregnancy.

Glycosuria, proteinuria, and aminoaciduria found in pregnancy also facilitate bacterial growth.

Acute pyelonephritis is confirmed by the presence of spiking fever (which sometimes reaches 104°F [40°C]), costovertebral angle tenderness, urinalysis findings with white blood cells and bacteria, and a urine culture result with positive growth of the causative organisms.

The scope of pyelonephritis may encompass many complications, including hyperthermia, anemia, leukocytosis, thrombocytopenia, decreased creatinine clearance, and adult respiratory distress syndrome. Fetal outcomes include low birth weight and prematurity.

Screening and diagnosis

Because asymptomatic bacteriuria is clinically significant in pregnancy, it should be aggressively sought, diagnosed, and treated in all stages. The various screening techniques used to detect bacteriuria include urinalysis, leukocyte esterase activity, a nitrite test, and urine cultures.


Any overt UTI or asymptomatic bacteriuria in pregnancy must be treated.
Sulfonamides, amoxicillin, amoxicillin-clavulanate, cephalexin, and nitrofurantoin are all acceptable antibiotics. However, avoid sulfonamides in the last few weeks of gestation in order to prevent kernicterus and hyperbilirubinemia in the newborn. 
A 7-day regimen eradicates bacteriuria in 70-80% of patients and is recommended for acute cystitis.
Single-dose therapy is less effective.
A 3-day course of treatment may provide the best balance of achieving adequate therapy and minimizing drug administration in pregnancy and is recommended for asymptomatic bacteriuria. 

Cystitis can generally be treated in the same manner as asymptomatic bacteriuria, Women treated for cystitis must be monitored with frequent urine cultures (at monthly intervals) because 25% of women who have cystitis experience another UTI during the course of their pregnancy.

Patients with pyelonephritis in pregnancy: Although mild cases may be treated in an outpatient setting, many of these women need hospitalization and require intravenous antibiotics in addition to parenteral hydration to combat nausea, vomiting, and dehydration.

Initial antibiotic therapy may be empirical, followed by tailoring to the pathogen grown in the urine.

Most patients show symptomatic improvement within 1-2 days of beginning therapy.

If no improvement is observed, consider resistant organisms, nephrolithiasis, abscess formation, and obstruction as causes of therapy failure. Follow-up care in women after an episode of acute pyelonephritis should be frequent with close monitoring of urine cultures.



Listeria monocytogenes is a gram-positive, aerobic, motile bacillus with aerobic and facultative anaerobic characteristics. The organism is found in soil and water and can be carried by animals that do not appear ill, leading to contamination of food of animal origin such as meats and dairy products. Unpasteurized raw milks are also sources of Listeria organisms. 


Pregnant women are 20 times more likely to contract listeriosis, and approximately one third of all cases of listeriosis occur during pregnancy. Transmission has mainly been by contaminated food, although rare cases of nosocomial transmission and transmission by direct contact with infected animals (which causes a local disease of the skin) have been noted. 

The organism is found in soil and water. Vegetables become contaminated from the use of fertilizer, while animals may be asymptomatic carriers transmitting disease to individuals who eat their infected meat.

Outbreaks of listeriosis are still reported. Contaminated turkey meat caused a multistate outbreak in 2002 and led to 46 cases with 7 deaths and 2 stillbirths.

Clinical spectrum
Pregnant patients with listeriosis are often asymptomatic, or, they may have a febrile illness similar to influenza with symptoms of fever, muscle aches, and, sometimes, nausea or diarrhea during the bacteremic phase of the disease. Although the symptoms may be mild during pregnancy, listeriosis can still lead to premature delivery, infection of the newborn, or even stillbirth.
Placental transfer of the organism to the fetus can cause amnionitis, which usually results in either spontaneous septic abortion or premature labor with delivery of an infected baby. Fetal infection may manifest as septicemia, meningoencephalitis, or disseminated granulomatous lesions with microabscesses.

In neonates, the mortality rate is approximately 50%. Mortality is more likely in early-onset neonatal sepsis. Late-onset listeriosis typically manifests as meningitis at age 3-4 weeks

CDC recommendations for prevention

Thoroughly cook raw food from animal sources.

Thoroughly wash raw vegetables before eating.

Keep uncooked meats separate from vegetables, cooked foods, and ready-to-eat foods.

Avoid unpasteurized milk or foods made from raw milk.

Wash hands, knives, and cutting boards after handling uncooked foods.

Avoid soft cheeses.

Cook leftover food or ready-to-eat foods until they are steaming hot.

Results of blood and cerebrospinal fluid cultures are positive in 60-75% of cases when central nervous system infection is present as indicated by fever or meningeal symptoms. Serological testing is not reliable for confirming a diagnosis, and stool cultures are not sensitive or specific.


Ampicillin is the drug of choice for treating listeriosis; a 2-week course is required for bacteremia. A dose of 2 g every 4 hours is recommended.

Trimethoprim/sulfamethoxazole, the usual alternative for penicillin-allergic patients, has not been approved for use in pregnancy.


Caused by Treponema pallidum a helical, tightly coiled, motile spirochete..

Treponemes appear able to cross the placenta at any time during pregnancy, thereby infecting the fetus.

Early diagnosis and treatment are extremely important for preventing the effects syphilis may have on pregnant women and their infants. Untreated primary or secondary syphilis in pregnant women can lead to congenital syphilis in 40-50% of cases.
Lack of prenatal care and failure to properly diagnose and treat syphilis in the mother are the most important factors leading to congenital syphilis, and these areas should be the focus of preventive efforts.

Clinical spectrum

The stage of maternal disease during which the fetus is exposed to infection determines the morbidity; the earlier the disease stage, the higher the morbidity. Untreated primary or secondary syphilis in pregnancy causes almost a 100% rate of infection in the fetus. The disease can cause stillbirth, neonatal death, or congenital syphilis.

The stages of disease mirror the stages in nonpregnant women. In the first stage, primary syphilis, a hard, painless red ulcer forms on the vulva, cervix, or vagina. Secondary syphilis predominantly manifests as a nonpruritic rash that may involve the palms and soles. Fever and joint pain are less common manifestations of secondary syphilis. The latent phase causes no symptoms, and, although the disease may not be transmitted to sexual partners, it is still transmissible to the fetus. One third of patients may progress to tertiary syphilis, during which the organism can damage the heart, eyes, brain, nervous system, bones, or joints.


Even when syphilis is considered unlikely, routine antenatal screening is warranted for prevention and surveillance. The earlier in pregnancy the treatment, the more efficacious it is. Therefore, serologic tests should be performed at the initial prenatal visit. If the patient is considered to be at high risk, tests should be repeated at 28 weeks' gestation and at delivery.
The nontreponemal antibody tests are generally used for screening. These tests are highly sensitive but are nonspecific. They include the rapid plasmin reagin and VDRL tests. Pregnancy often causes false-positive nontreponemal antibody test results; therefore, positive findings should be confirmed with specific antitreponemal antibody tests such as the microhemagglutination assay-T pallidum and the fluorescent treponemal antibody absorption test.

The diagnosis can be made in the same manner as for a nonpregnant woman. In primary syphilis, the diagnosis can be confirmed by identifying T pallidum in dark-field examination of material taken from a lesion. Because most pregnant women do not have visible lesions, serologic screening as mentioned previously is the primary means of establishing the diagnosis.


Once a diagnosis is made, consider other sexually transmitted diseases before starting treatment. Treatment is the same as for nonpregnant women, with a single dose of 2.4 million U of benzathine penicillin for primary and secondary syphilis, but some experts recommend a second dose of benzathine penicillin G 1 week after the initial dose, especially in the third trimester or in the case of secondary syphilis.

In latent syphilis, treatment consists of 3 doses of benzathine penicillin (as for nonpregnant women). If results of the monthly quantitative VDRL or equivalent test show a 4-fold increase, re-treat the patient and perform a lumbar puncture to rule out neurosyphilis. 

Penicillin-allergic women must be desensitized and then treated with penicillin because the accepted alternatives to treatment are erythromycin and tetracycline. Erythromycin may not prevent congenital syphilis, and tetracycline and doxycycline are not recommended for pregnant women.
Using penicillin therapy in pregnant women with early syphilis can cause a Jarisch-Herxheimer reaction. Pregnant women, apart from the usual manifestations, can present with uterine contractions, preterm labor, and premature delivery.


Chlamydia trachomatis - obligate, intracellular bacterium with 15 immunotypes:

A-C - trachoma

D-K - genital tract infections

L1-L3 - lymphogranuloma venereum

One of the leading causes of infertility in women. 


Chlamydia trachomatis is an obligate intracellular organism. Initially considered a virus, it is now classified as a bacterium based on its sensitivity to antibiotics and its reproduction cycle.


The usual mode of transmission to the fetus is vertical during the second stage of labor. The major routes of entry are the eye and the nasopharynx.

Clinical spectrum
Approximately 75% of women with chlamydia are asymptomatic.
The disease can cause endometritis, cervicitis, acute PID, and acute urethral syndrome in all women and chorioamnionitis, postpartum endometritis, and gestational bleeding in pregnant women.


Chlamydial cervicitis should be considered in the presence of a yellow or green vaginal discharge, greater than 10 polymorphonuclear leukocytes per high-power field, and bleeding or edema of the cervix.

The following are the accepted screening methods according to the CDC:

A nucleic acid amplification test performed on an endocervical swab specimen or on urine

An unamplified nucleic acid hybridization test, an enzyme immunoassay, or direct fluorescent antibody test performed on an endocervical swab specimen

Culture performed on an endocervical swab specimen

Monoclonal antibodies labeled with fluorescein to detect elementary bodies of Chlamydia species (MicroTrak) or enzyme-linked immunosorbent assay is used for screening.


In asymptomatic women with positive culture findings and in symptomatic women,

500 mg of erythromycin 4 times daily for 7 days is the treatment of choice.

Single-dose therapy with 1 g of azithromycin is an alternative.

Tetracycline, the drug of choice for treating chlamydia in other situations, is contraindicated in pregnancy. Retest treated women after 3-4 weeks, and evaluate and treat sexual contacts.


Gonorrhea is caused by Neisseria gonorrhoeae, a gram-negative diplococcus.

Gonorrhea is transmitted vertically during the birth process. No evidence suggests placental transmission

Gonococcal infections cause no symptoms in approximately 50% of patients and thus warrant screening in pregnancy.

Clinical spectrum

Gonorrhea can infect the uterus, cervix, and fallopian tubes, leading to ectopic pregnancy and infertility.

During pregnancy, women with gonorrhea may be asymptomatic, although reports have been received of endocervicitis, premature rupture of membranes, chorioamnionitis, septic abortion, intrauterine growth retardation, prematurity, and postpartum sepsis. 

Newborns exposed to gonorrhea during vaginal delivery can develop an acute conjunctivitis known as ophthalmia neonatorum.
Pregnancy is a predisposing factor in the development of disseminated gonococcal infection. The classic presentation of disseminated disease is the triad of arthritis, skin lesions, and fever. The rash is vesicular and pustular, usually over the distal joints.


A Gram stain of the endocervical secretions should be performed when an immediate diagnosis is necessary. Gram-negative diplococci in polymorphonuclear leukocytes are diagnostic.

A culture specimen should be taken directly from the endocervix onto Thayer-Martin media. Other sites, such as the pharynx, rectum, and urethra, should also be cultured as indicated.
Enzyme immunoassay is another rapid means of diagnosis.


The treatment of choice for uncomplicated cervicitis is a single dose of 250 mg of ceftriaxone intramuscularly. Penicillin-allergic pregnant women can be treated with spectinomycin. Although ciprofloxacin is one of the standard drugs of choice, it is contraindicated in pregnancy.

All patients treated for gonococcal infection should also be empirically treated for chlamydial infection.

Bacterial vaginosis is an infection caused by excessive growth of bacteria that may normally be present in the vagina.
In the United States, the rate of bacterial vaginosis in pregnancy is approximately 16%
Infection can be transmitted via the placenta to the fetus and cause intrauterine fetal death. 


The etiology is polymicrobial in nature and is associated with G vaginalis, Bacteroides species, Mobiluncus species, Peptococcus species, and Mycoplasma hominis.

Clinical spectrum

Abnormal vaginal discharge with an unpleasant, fishlike odor, especially after sexual intercourse. The discharge is generally white or gray, and women may have dysuria or itching around the vagina.

The bacteria can ascend and colonize the amniotic membranes, decreasing the tensile strength of the membranes and causing the weakened membranes to rupture. G vaginalis can also cause prostaglandin production and lead to premature labor unresponsive to tocolytic therapy.


When using the clinical criteria, 3 of the following 4 should be present:

A homogenous, white, noninflammatory discharge that smoothly coats the vaginal wall

Clue cells, ie, vaginal epithelial cells that have a stippled appearance due to aggregates of coccobacilli

Vaginal fluid pH of more than 4.5

A positive whiff test result, ie, a fishy odor to the vaginal discharge before or after the addition of 10% potassium hydroxide solution
When using Gram stain to make a diagnosis, determine the relative concentration of the bacterial morphotypes characteristic of the altered flora of bacterial vaginosis.

Metronidazole at 500 mg twice a day for 7 days or metronidazole gel 0.75% intravaginally twice a day for 5 days is the treatment of choice. Avoid the gel in the first trimester of pregnancy.

Clindamycin 300 mg twice a day for 7 days

Antibiotic Use During Pregnancy And Birth Defects: Study Examines Associations

Crider and her colleagues (2009) analyzed data on more than 13,000 women whose babies had one of more than 30 birth defects. They compared the women's rates of antibiotic usage, from the month leading up to pregnancy through the end of the first trimester, with that of almost 5,000 women whose children did not have a birth defect.

November 2009, Archives of Pediatrics & Adolescent Medicine
Although penicillin and several other antibacterial medications commonly taken by pregnant women do not appear to be associated with many birth defects, other antibiotics, such as sulfonamides and nitrofurantoins, may be associated with several severe birth defects and require additional scrutiny, a new study has found

November 2009, Archives of Pediatrics & Adolescent Medicine

Antibiotics (anti-microbials)
Commonly used antibiotics

Penicillins (category B): These are the most widely used antibiotics in pregnancy because of their wide margin of safety and lack of known toxicity. In the collaborative perinatal project, 3546 women used penicillin during the first trimester and no adverse effects were demonstrated. Ticarcillin, however, has shown some toxicity in animals and may not be safe in pregnancy.

Cephalosporins (category B): This group has not been well studied in the first trimester and should therefore not be considered the first line of treatment in the first trimester of pregnancy. Generally, these drugs are considered safe and have shown no teratogenicity

Sulfonamides (category C): Avoid sulfonamides in the third trimester of pregnancy and during breastfeeding. Although these agents cause no known damage in utero, they can cause hyperbilirubinemia and kernicterus if the drug is still present in the neonate after birth. In mothers with G-6-PD deficiency, sulfonamide use has been associated with hemolysis. The combination of sulfonamides with trimethoprim in the first trimester has been associated with cardiovascular birth defects.

Sulfonamides were also tied to an increased risk for hypoplastic left heart syndrome and coarctation of the aorta, choanal atresia (a blockage of the nasal passage), transverse limb deficiency , diaphragmatic hernia and anencephaly

November 2009, Archives of Pediatrics & Adolescent Medicine

Tetracyclines (category D):

-Pregnant women are susceptible to acute fatty necrosis of the liver, pancreatitis, and renal damage.

-In the fetus, these agents can cause stunting of growth, discoloration of teeth, and hypoplasia of dental enamel.

Nitrofurantoin (category B): The collaborative perinatal project showed no increased risk of anomalies in 590 women who were exposed to the drug. In mothers with G-6-PD deficiency, it has caused hemolysis in both the mother and the fetus and should therefore be avoided near delivery.

Nitrofurantoins were also associated with multiple birth defects, including anophthalmia and microphthalmos , a cleft lip or cleft palate and several congenital heart defects

November 2009, Archives of Pediatrics & Adolescent Medicine

Quinolones (category C): Although animal studies have shown arthropathies, no human studies have been conducted and no cases of teratogenicity have been reported. These agents have a high affinity for bone and cartilage.

Metronidazole (category B): Metronidazole should not be used in the first trimester or during lactation. When used in the second or third trimester, large single-dose treatments should be avoided.

Macrolides (category B): These agents have not been associated with birth defects and are considered safe for use in pregnancy.

Clindamycin (category B): This drug has not been associated with birth defects

Friday, March 11, 2011

Ovarian Hyperstimulation Syndrome

Background Definition Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic complication of assisted reproduction technology. OHSS usually develops several days after assisted ovulation following gonadotropin therapy. This syndrome is characterized by ovarian enlargement due to multiple ovarian cysts and an acute fluid shift into the extravascular space. Results include ascites, hemoconcentration, hypovolemia, and electrolyte imbalances. The prevalence of therapy with assisted reproduction technology is increasing. Therefore, gynecologists, internists, and emergency physicians must be aware of this rare condition and its myriad of clinical presentations, which can cause multiorgan dysfunction and, potentially, death Classification To understand OHSS and its management, one must first be aware of its classifications of severity.
Grades of OHSS are as follows: Mild OHSS Grade 1 - Abdominal distention and discomfort Grade 2 - Grade 1 disease plus nausea, vomiting, and/or diarrhea plus ovarian enlargement from 5-12 cm Moderate OHSS Grade 3 - Features of mild OHSS plus ultrasonographic evidence of ascites Severe OHSS Grade 4 - Features of moderate OHSS plus clinical evidence of ascites and/or hydrothorax and breathing difficulties Grade 5 - All of the above plus a change in the blood volume, increased blood viscosity due to hemoconcentration, coagulation abnormalities, and diminished renal perfusion and function Pathophysiology The pathogenesis of ovarian hyperstimulation syndrome is unknown, but the process is related to increased vascular permeability in the region surrounding the ovaries and their vasculature
Beta-human chorionic gonadotropin (hCG) and its analogs, estrogen, estradiol, prolactin, histamine, and prostaglandins have all been implicated in the past. Vasoactive substances such as interleukins, tumor necrosis factor (TNF)-alpha, endothelin-1, and vascular endothelial growth factor (VEGF) secreted by the ovaries have been implicated in increasing vascular permeability. Withholding hCG decreases OHSS. Hence, it plays a critical role in enhancing ovarian angiogenesis and triggering the cascade of vascular permeability in ovarian vessels that leads to third spacing and OHSS. Both exogenous and endogenous gonadotropins from molar pregnancy, gonadotroph adenomas, and even pregnancy can aggravate OHSS.These changes in the ovarian vasculature are exaggerated responses to normal luteinizing hormone (LH). The function of hCG is similar to that of LH. As a result, the actions of hCG mimic these changes. Moreover, hCG exerts a follicle stimulating hormone–like action in stimulating the ovaries. In addition, it has a prolonged half-life. All of these properties of hCG lead to ovarian stimulation and changes in periovarian vasculature even after ovulation. These effects lead to poor control of the induction process, initiating and/or aggravating OHSS. Abdominal pain, nausea, and vomiting Enlargement of the ovaries causes abdominal pain, nausea, and vomiting. The enlargement is sometimes as much as 25 cm. Another consequence is discomfort resulting from increased intra-abdominal pressure due to ascites. Ascites and tense distention Ascites and tense distention occur because of the extravasation of protein-rich fluid and increasing leakage from the intravascular space due to an osmolar differential. Leakage of fluid from follicles, increased capillary permeability leading to third spacing (due to the release of vasoactive substances), or frank rupture of follicles can all cause ascites. Localized or generalized peritonitis Localized or generalized peritonitis is caused by peritoneal irritation secondary to blood from ruptured cysts, protein-rich fluid, and inflammatory mediators. Acute abdominal pain Acute abdominal pain may be due to ovarian torsion, intraperitoneal hemorrhage, or rupture of cysts secondary to enlarged ovaries with fragile walls. Hypotension and/or hypovolemia Follicular fluid and perifollicular blood containing large amounts of VEGF, which is thought to increase vascular permeability, escapes into the peritoneal cavity. The fluid is then absorbed into the general vascular bed. Blood vessels both within and outside the ovary become functionally impaired, and the result is the leakage of fluid through those vessels and a massive fluid shift from the intravascular bed to the third compartment. This process results in intravascular hypovolemia with the concomitant development of edema, ascites, hydrothorax, and/or hydropericardium. Hypotension and/or hypovolemia are also caused by compression of the inferior vena cava because of enlarged cysts or ascites. As a result, both venous return and preload decrease. Eventual outcomes are decreased cardiac output and hypotension. Dyspnea Pulmonary function may be compromised as enlarged ovaries and ascites restrict diaphragmatic movement. Other possible causes of dyspnea are the relatively rare manifestations of OHSS, such as pleural effusion, pulmonary edema, atelectasis, pulmonary embolism, acute respiratory distress syndrome (ARDS), and pericardial effusion. Hypercoagulable state A hypercoagulable state is likely due to hemoconcentration and hypovolemia resulting from third spacing and fluid shift. It is also related to increased estrogen levels. Patients have an increased risk of developing deep venous thromboses and pulmonary embolisms. Electrolyte imbalance Electrolyte imbalance occurs due to the extravasation of fluid and resultant renal dysfunction resulting from decreased perfusion. Increased reabsorption of sodium and water occurs in the proximal tubule, leading to oliguria and low urinary sodium excretion. The exchange of hydrogen and potassium for sodium in the distal tubule is reduced. As a result, hydrogen and potassium ions accumulate and cause hyperkalemia and a tendency to develop acidosis. Compensatory and electrolyte-retaining mechanisms fail. Acute renal failure The hypovolemia of OHSS leads to hemoconcentration and creates a hypercoagulable state. Microthrombi form in tubules, leading to decreased renal perfusion. Acute renal failure may result. Frequency International The rate of ovarian hyperstimulation syndrome depends on definitions, risk factors, stimulation protocols, and conception. Rates of OHSS are as follows:
Mild, 8-23% Moderate, 1-7% Severe, 0.25-5% The frequency of OHSS may increase if the ovary is overstimulated, as documented by high levels of estradiol and depicted as increased number of follicles on ultrasonography. The incidence is increased when protocols combine luteinizing hormone-releasing hormone (LHRH) agonists and gonadotropins, as compared with gonadotropins alone, to induce ovulation. In the ideal situation, induction should stimulate the ovaries to a desired level. However, the unpredictable response of the ovaries to induction make the prediction and prevention of OHSS difficult.Hence, heightened clinical suspicion and early intervention are paramount for decreasing morbidity and mortality. Women of young age, as well as those with low body weight, polycystic ovarian syndrome, or previous episodes of hyperstimulation are all at increased risk for developing OHSS. In addition, an increased number of small- and medium-sized follicles and elevated estradiol levels around the assumed time of ovulation increase the incidence. According to Martin et al, if the pre-hCG estradiol amount is greater than 6000 mcg and/or if more than 30 follicles are present, the rate of severe OHSS approaches 80%.[11 ] Mortality/Morbidity Morbidity may be clinically significant in cases of severe and critical ovarian hyperstimulation syndrome, and fatalities do occur. Race No racial predisposition is reported in ovarian hyperstimulation syndrome. Sex Ovarian hyperstimulation syndrome affects only women. Age Only women of childbearing age are affected by ovarian hyperstimulation syndrome. The risk is increased in younger women. Clinical History The patient who has ovarian hyperstimulation syndrome (OHSS) is a woman who recently had gonadotropin stimulation to induce ovulation or one who was treated with assisted reproductive technologies such as in vitro fertilization. Early OHSS is usually moderate or severe and manifests 3-7 days after the administration of hCG. Late OHSS is usually severe and occurs 12-17 days after hCG treatment.The former type is due to exogenously administered hormone, and the latter often occurs during an implanting or implanted pregnancy because pregnancy hCG exacerbates the disease. Signs of OHSS Signs of OHSS include the features listed below.(Percentages refer to all classes of OHSS.) -Ascites -Hypercoagulability (6.2%) -Thrombosis -Pleural effusion and pericardial effusion -Hemoconcentration -Leukocytosis (WBC count, >20,000/mm3) -Electrolyte abnormalities (eg, hyponatremia, hyperkalemia) -Elevated transaminase values (26%) -Acute respiratory distress syndrome (2%) -Pulmonary embolism (2%) -Acute renal failure (1%) Symptoms of OHSS Symptoms of OHSS include those listed below.(Percentages refer to cases of severe OHSS.) -Shortness of breath (92%) -Abdominal discomfort (99%) -GI disturbances - Nausea, vomiting, diarrhea (54%) -Oliguria (30%) -Peripheral edema (13%) -Lethargy -Rapid weight gain -Although OHSS usually manifests with a constellation of symptoms, atypical presentations can occur. Rare presentations such as thromboembolism, both venous and arterial, have been observed. Atypical locations of venous thromboembolism include the internal jugular vein, the subclavian vein, the inferior vena cava, the ileofemoral veins, and the intracerebral veins. Other abnormal forms of presentation include isolated hydrothorax and isolated thromboembolism. Additional situations leading to elevated hCG concentrations, such as in molar pregnancy and gonadotroph adenomas may lead to mild forms of OHSS in rare cases. Physical Physical findings of ovarian hyperstimulation syndrome include right or left lower quadrant pain below the umbilicus, as well as edema. Of note, abdominal palpation must be performed gently to avoid the possibility of rupturing a large cyst. Pelvic examination should be deferred in favor of ultrasonography of the pelvis. Causes No single cause of ovarian hyperstimulation syndrome has been identified. The etiology appears to be multifactorial, though the cardinal events are ovarian enlargement, ascites, and hypovolemia. The hormone hCG and its analogs estrogen, estradiol, histamine, TNF-alpha, endothelin-1, and especially VEGF have all been implicated in OHSS.Increased vascular permeability in periovarian vasculature brought about by the factors described above plays an important role in OHSS.A young age, a decreased body mass index, and a history of OHSS increase the risk. Exogenous induction agents (recombinant hCG) precipitates OHSS more than endogenous agents (gonadotropin-releasing hormone [GnRH] analogs). Other precipitating factors are induction in a hyperestrogenic state and poor timing. Differential Diagnoses Acute Respiratory Distress Syndrome Pelvic Inflammatory Disease/Tubo-ovarian Abscess Appendicitis Pericardial Effusion Appendicitis, Acute Peritonitis and Abdominal Sepsis Cholecystitis Pleural Effusion Ectopic Pregnancy Pulmonary Embolism Ovarian Cysts Salpingitis Ovarian Torsion Hemorrhagic cyst
Pulmonary edema
Ruptured ovarian cyst Workup Laboratory Studies In ovarian hyperstimulation syndrome (OHSS), the hematocrit is the most important measure in deciding if a patient should be hospitalized. If the patient's hematocrit level is greater than 60% and if she has ascites, hospitalize her immediately. Laboratory monitoring may involve the following parameters: -CBC with differential: This is helpful because decreased intravascular volume leads to hemoconcentration and an increased hematocrit. -Complete metabolic panel -Liver function: Liver function is decreased, as indicated by increased concentrations of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase. -Kidney function: Renal function is reduced, BUN and creatinine values are increased, whereas albumin and protein levels are decreased. Electrolyte imbalances, hyperkalemia, and acidosis may be present. -Coagulation profile, including the prothrombin time (PT), activated partial thromboplastin time (aPTT), and international normalized ratio (INR): These findings aid in detecting a hypercoagulable state and in monitoring anticoagulation. -Leukocyte count: This count is related to the seriousness of OHSS and to the risk of thromboembolism. -Beta-hCG concentration: A beta-hCG measurement is especially useful at more than 12 days after an injection of hCG. A positive result at this stage indicates pregnancy, an endogenous source of hCG for OHSS. hCG upregulates vascular endothelial growth factor (VEGF) receptors, and this upregulation increases third spacing.Mild OHSS may deteriorate to severe OHSS because of the increased availability of hCG. -Estradiol levels: Values are increased. -Laboratory findings of a serum estradiol concentration greater than 2000 pg/mL and a progesterone concentration greater than 30 ng/mL in the early part of the luteal phase are warning signs of developing OHSS. Signs that may indicate a progression in severity are increases in hCG level, hematocrit, hypoproteinemia, and hypoalbuminemia (third spacing). Additional signs are decreasing renal and liver function. OHSS is critical when the signs and symptoms of severe OHSS are present with any of the following findings: renal failure, ARDS, thromboembolism, or a hematocrit level greater than 60%.
Imaging Studies :
-Ultrasonography may be needed to measure the size of the ovaries, to assess the follicles, and to evaluate ascites
-Chest radiography may be indicated if dyspnea is present.
Treatment :
Treatment Based on Degree of Hyperstimulation Mild hyperstimulation Treatment for ovarian hyperstimulation syndrome (OHSS) is supportive, as needed. Mild ovarian hyperstimulation can develop into moderate or severe disease, especially if conception ensues. Therefore, women with mild disease should be observed for enlarging abdominal girth, acute weight gain, and abdominal discomfort on an ambulatory basis for at least 2 weeks or until menstrual bleeding occurs. Moderate hyperstimulation Treatment of moderate OHSS consists of observation, bed rest, provision of adequate fluids, and sonographic monitoring of the size of cysts. Serum electrolyte concentrations, hematocrits, and creatinine levels should also be evaluated. Some physicians have their outpatients keep track of their fluid intake and output. Intake or output less than 1000 mL/d or a discrepancy in fluid balance greater than 1000 mL/d is a cause for concern. The beginning of the resolution of OHSS is apparent when the cysts shrink, as seen on 2 consecutive ultrasonographic examinations, and when clinical symptoms recede. In contrast, early detection of progression to the severe form of the syndrome is marked by continuous weight gain (>2 lb/d), increased severity of existing symptoms, or appearance of new symptoms (eg, vomiting, diarrhea, or dyspnea). Severe hyperstimulation -Experience with severe OHSS is mandatory for appropriate treatment. One should transfer the patient to a different center if no one who is experienced in managing severe OHSS is available at the present location. -Severe OHSS is not common, but it is dangerous. Severe and critical forms of OHSS are potentially lethal disorders, and history taking and physical examination are paramount at the time of admission. In most clinical situations, patients require bed rest. Daily physical examination should consist of measuring the patient's weight and abdominal girth. Fluid balance must be assessed every 4 hours. -Medical treatment of severe hyperstimulation is directed at maintaining intravascular blood volume. Simultaneous goals are correcting the disturbed fluid and electrolyte balance, relieving secondary complications of ascites and hydrothorax, and preventing thromboembolic phenomena. -The main interventions are fluid management and correction of hypovolemia. These measures consists of initial fast intravenous administration of normal saline. Dextrose 5% in normal saline or normal saline is infused at a rate of 125-150 mL/h with 4-hour tabulations of urine production. If urine production is restored or improved, a maintenance protocol is started. The patient should be closely monitored for clinical signs of overhydration. If urine output is unsatisfactory, hyperosmolar intravenous therapy is indicated with an infusion of 200 mL of 25% human albumin. The use of diuretics in patients with low urine production and hypovolemia is counterproductive and dangerous. -Close surveillance of fluid management is necessary. Intravenous fluid administration is stopped when urine production, appetite, or interest in drinking increases and when an overall clinical improvement is observed. In the resolution phase of severe OHSS, the patient's fluid intake should be restricted to avoid renewed hemodilution. -To prevent thrombosis, subcutaneous heparin 5000-7500 U/d is begun on the first day of admission. It is stopped after adequate mobilization is achieved. -To manage ascites, ultrasonographic-guided vaginal paracentesis is indicated if the patient has severe discomfort or pain or if she has pulmonary or renal compromise.The procedure entails the same setup as that used for transvaginal follicular puncture. Whelan and Vlahos advise that an anesthesiologist be present. Paracentesis may be repeated if required. Critical hyperstimulation Critical OHSS may include renal failure, hepatic damage, thromboembolic phenomena, ARDS, and multiorgan failure.Its management and treatment requires intensive care in a critical care unit. Intensive care should include invasive monitoring of circulatory indicators, including venous pressure and wedge pressure. The patient may need extra oxygenation (assisted ventilation). If renal failure is present, an intravenous dopamine regimen should be started. To treat thromboembolism, therapeutic doses of anticoagulants should be administered. Thoracocentesis should be performed in the case of severe hydrothorax. Finally, if a pregnancy is maintaining a life-threatening OHSS, therapeutic abortion must be considered. Clinical Pearls What not to do Aggressive palpation of the abdomen: This can precipitate follicular rupture. Early surgical intervention: Early surgery may cause extensive bleeding from ovarian cysts. However, surgery is mandated if torsion or rupture has occurred. Neglect of deterioration in organs and systems: Remember that OHSS is a syndrome of multiorgan dysfunction. What to do Maintain a high degree of clinical suspicion and a low threshold for admission. Implement early surgical intervention in cases of ovarian torsion or hemorrhage. Perform paracentesis to address ascites. This decreases pressure on inferior vena cava and diaphragm. Place a transthoracic tube to manage pleural effusions. Resolution After several days, third-space fluid begins to re-enter the intravascular space, hemoconcentration reverses, and natural diuresis ensues. Intravenous fluids may be tapered as the patient's oral intake increases. Complete resolution typically takes 10-14 days from the onset of initial symptoms. Careful maintenance of blood volume, correction of electrolyte imbalances, and relief of secondary complications of ascites and hydrothorax are generally sufficient to support the patient during the severe phase of ovarian hyperstimulation. Anticoagulant therapy is usually unnecessary if these therapies are promptly administered. Blood coagulation may be monitored because of the danger of disseminated intravascular clotting. Surgical Care Ovarian hyperstimulation syndrome is a self-limiting disease. Therefore, treatment should be conservative and directed at symptoms. Medical therapy suffices for most patients. Women with severe symptoms often require intensive medical care. Surgery is necessary only in extreme cases, such as in the case of a ruptured cyst, ovarian torsion, or internal hemorrhage. Surgical management further aggravates electrolyte imbalances and increases morbidity. Ascites can be tapped by means of paracentesis. Harvesting of eggs in women with OHSS can lead to hemorrhage and peritonitis. However, tapping follicles when they are of moderate size may prevent OHSS. Laparotomy during torsion and intraperitoneal hemorrhage is life saving and recommended. Consultations In severe cases of OHSS, consultation with a physician specializing in fluid and electrolyte imbalances is warranted. For some cases, aggressive treatment in the surgical intensive care unit may be required. Diet Ensure that patient receives plenty of hydration. Activity Activity should be minimal. Physical examination should be performed gently because of the tendency of follicles to rupture.
Medication :
Medical therapy is aimed at the correction of fluid and electrolyte balance. Thrombosis can occur in the arteries (25%) and veins (75%). Therefore, use of heparin, low molecular weight heparin (enoxaparin sodium [Lovenox]), antiembolism stockings, and sequential compression devices (boots) are all recommended as prophylaxis against thrombosis. Heparin prophylaxis is usually started in patients with a history of thrombosis, factor V Leiden deficiency, or other thrombophilic states before the induction of ovulation. Anticoagulant These agents inhibit key factors involved in thrombogenesis.
Heparin Augments activity of antithrombin III and prevents conversion of fibrinogen to fibrin. Does not actively lyse but can inhibit further thrombogenesis. Prevents reaccumulation of clot after spontaneous fibrinolysis. Dosing Adult 5000-7500 U SC qd Interactions Digoxin, nicotine, tetracycline, and antihistamines may decrease effects; nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin, dextran, dipyridamole, and hydroxychloroquine may increase heparin toxicity Contraindications Documented hypersensitivity; subacute bacterial endocarditis, active bleeding, history of heparin-induced thrombocytopenia Precautions Pregnancy C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Electrolyte supplement, parenteral Used to replenish intravascular and extravascular volume.
Normal saline Used to restore interstitial and intravascular volume. Dosing Adult 1-2 L IV initially, given as fast bolus; assess hemodynamic response, then 125-150 mL/h until urine production improves; followed by maintenance dose Interactions May decrease lithium levels when administered concurrently Contraindications Edema in brain or lungs (pulmonary edema may contribute to ARDS); hypernatremia Precautions Pregnancy A - Fetal risk not revealed in controlled studies in humans Precautions Exercise caution to prevent fluid overload; monitor cardiovascular and pulmonary function; stop fluids when desired hemodynamic response observed or pulmonary edema develops; interstitial edema may occur; caution in congestive heart failure, hypertension, edema, liver cirrhosis, or renal insufficiency Blood product derivatives These agents are used to expand plasma volume. Albumin (Albuminar, Albumisol, Albunex, Albutein, Buminate) Major plasma protein responsible for colloid oncotic pressure of blood. Pooled from blood, serum, plasma, or placenta from healthy donors. Given in certain types of shock or impending shock. Use 5% solution to expand plasma volume and maintain cardiac output. Use 25% solution to raise oncotic pressure. Dosing Adult 200 mL of 25% solution IV over 20-30 min, then assess hemodynamic and renal response Interactions None reported Contraindications Documented hypersensitivity; pulmonary edema; severe congestive heart failure or anemia; protein load of 5% albumin (tends to exacerbate renal insufficiency, a potential complication of septic shock) Precautions Pregnancy C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus Precautions Caution in renal or hepatic failure, may cause protein overload; rapid infusion may cause vascular overload or hypotension; monitor for volume overload; caution in sodium-restricted patients; common adverse effects include congestive heart failure, hypotension, tachycardia, fever, chills, and pulmonary edema; do not dilute albumin 25% with sterile water for injection (produces hypotonic solution and, if administered, may result in life-threatening hemolysis and acute renal failure) Adrenergic agonist agent These agents increase blood pressure. Dopamine (Intropin) Naturally occurring endogenous catecholamine that stimulates beta1-adrenergic, alpha1-adrenergic, and dopaminergic receptors in dose-dependent fashion; stimulates release of norepinephrine.At low dosages (2-5 mcg/kg/min), acts on dopaminergic receptors in renal and splanchnic vascular beds, causing vasodilation-selective dilation of renal vasculature, enhancing renal perfusion. Also reduces sodium absorption, decreasing energy requirement of damaged tubules. This enhances urine flow, which, in turn, helps prevent tubular cast obstruction. Most clinical studies have failed to establish this beneficial role of renal-dose dopamine infusion.At midrange dosages (5-15 mcg/kg/min), acts on beta-adrenergic receptors to increase heart rate and contractility.At high dosages (15-20 mcg/kg/min), acts on alpha-adrenergic receptors to increase systemic vascular resistance and raise blood pressure. Dosing Adult 1-5 mcg/kg/min IV Interactions Monoamine oxidase inhibitors (MAOIs) may prolong effects; beta-blockers may antagonize peripheral vasoconstriction caused by high doses; butyrophenones (eg, haloperidol) and phenothiazines can suppress dopaminergic renal and mesenteric vasodilation induced with low-dose infusion; low doses concurrently administered with diuretics may produce additive effects on urine flow; hypotension and bradycardia may occur with phenytoin; may decrease effects of phenytoin Contraindications Documented hypersensitivity; pheochromocytoma or ventricular fibrillation Precautions Pregnancy C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus Precautions Closely monitor urine flow, cardiac output, pulmonary wedge pressure, and blood pressure during infusion; before infusion, correct hypovolemia with whole blood or plasma, as indicated; monitoring of central venous pressure or left ventricular filling pressure may help in detecting and treating hypovolemia; in patients who have received MAOIs the last 2-3 weeks, doses should not exceed 1/10th the initial dose of dopamine; ventricular arrhythmias and hypertension may occur in patients receiving cyclopropane or halogenated hydrocarbon anesthetics
Follow-up Deterrence/Prevention -Ovarian hyperstimulation syndrome (OHSS) is a self-limiting disease of the luteal phase. Without luteinizing hormone (LH) or its imitator hCG, ovulation or the luteal phase does not occur. Avoidance of hCG during ovarian stimulation offers an opportunity to prevent OHSS in high-risk patients. However, those patients do not conceive. Other options are delaying hCG (coasting) for 1-3 days until estradiol levels plateau or decline (<2500 pg/mL), using a GnRH agonist to induce ovulation, or lowering doses of hCG. -The best preventive method is to adapt the treatment and to closely monitor patients at risk. Remember that women at risk are those with high levels of estrogen and many follicles at the assumed time of ovulation. Patients with polycystic ovarian syndrome should be closely monitored as well. -Laboratory findings of a serum estradiol concentration greater than 2000 pg/mL and a progesterone concentration greater than 30 ng/mL in the early part of the luteal phase are warning signs of developing OHSS. -Vaginal intercourse is restricted in women with any grade of OHSS because of the risk of rupturing a cyst. Patients should also avoid impact-type activities or strenuous exertion. Prognosis The prognosis is excellent if ovarian hyperstimulation syndrome is mild or moderate. In severe OHSS, the prognosis is optimistic if good treatment is given. Hypercoagulability may endanger the patient. Death from OHSS is largely due to hypovolemic shock and electrolyte imbalance, hemorrhage, and thromboemboli. Estimated fatality rates are 1 per 400,000-500,000 stimulated cycles. Patient Education Patients are instructed to record their weight on a daily basis, to avoid exercise and intercourse, and to maintain adequate hydration after in vitro fertilization. They should measure their abdominal girth, intake, and output, and they should report urinary output of less than 1000 mL in any 24-hour period. Patients are educated to report progressive bloating, abdominal discomfort, decreases or increases in urination, cramping, dizziness, shortness of breath, and weight gain of more than 5 lb/wk.

Wednesday, January 9, 2008

Prenatal Diagnosis of Chromosomal Anomalies /DR. Alaa Mosbah , MD OBS & GYN

Introduction : Prenatal diagnosis of chromosomal anomalies employs a variety of techniques either as a screening procedure for relatively prevalent disorders or as a diagnostic procedure for known familial conditions. The former identifies an increased likelihood of a fetal abnormality in an apparently normal pregnancy, whereas the latter confirms or refutes the existence of an actual anomaly in a fetus believed to be at increased risk . Currently available prenatal non-invasive screening tests are ultrasonography and various biochemical tests, while CVS, amniocentesis, and fetal blood sampling are invasive diagnostic procedures. High-risk pregnancies : include the following 1. Advanced maternal age (age 35 years or more at estimated date of delivery). Some authors also consider paternal age of approximately 50 years or older. 2. Family history (self, spouse, child, parent or sibling) of previous birth of a child with chromosome abnormality / multiple structural defects / ONTDs, or metabolic disorder. 3. Suspicious biochemical results. 4. Abnormal morphological scan. 5. Parent with a chromosome disorder. 6. Parent who are carriers of specific genetic defects such as cystic fibrosis, Tay-Sach dystrophy, sickle cell anemia, Falconis anemia&thalassaemia The most common reason for prenatal diagnosis of chromosome abnormalities is to look for evidence of trisomies, Turner syndrome and triploidy. Trisomy 13, 18, and 21 are the most common, with trisomy 21 comprising about half of all the trisomies identified. Various screening and diagnostic procedures used to detect common chromosomal abnormalities are discussed here. Screening procedures : Non invasive diagnostic procedures : 1.Ultrasonography Ultrasound scanning is offered to all pregnant women. It is non-invasive and has no inherent procedure related loss. First-trimester sonography is offered mainly to confirm the gestational age, to identify singleton or multiple pregnancy and to measure nuchal thickness (NT). Second-trimester ultrasound is generally recommended at 19 to 21 weeks to detect fetal structural defects. Nuchal translucency (NT) : NT refers to the subcutaneous space between the skin and the cervical spine in the fetus. The ultrasonographic findings of NT in the first-trimester of the pregnancy reportedly has been associated with fetal chromosome abnormalities including trisomies 21,18,13 and triploidy and Turner syndrome (45XO). Among karyotypically normal fetuses increased NT may be related to certain birth defects including cardiac septal defects, diaphragmatic hernia, renal defects, omphalocele, body-stalk anomaly, fetal akinesia syndrome, and certain skeletal dysplasias. Certain genetic defects and infections may also lead to increased NT. Various genetic defects associated with increased NT are Arthrogryposis, Noonan's syndrome, Smith-Lemli-Opitz syndrome, Stickler syndrome, Jarco-Levine syndrome, Miller-Dieker syndrome. Increased NT may be found in a normal fetus. Therefore, increased NT does not mean that the fetus is chromosomally abnormal but it does mean an increased risk for some disorders and birth defects. NT measurements can be taken from the sagittal section of the fetus usually used to obtain the crown-rump length, or from a transverse suboccipitobregmatic view of the fetal head. NT values are crown-rump-length-dependent. Measurements equal to or more than 3mm in the first-trimester and more than 6mm in the second-trimester are considered as abnormal. NT is apparently a powerful tool for the detection of aneupolidy, particularly Down's syndrome. For isolated nuchal edema, the risk for trisomy 21 may be 15 times the background. The estimated detection rate for Down's syndrome using NT at 10 to 14 weeks of gestation combined with maternal age is about 80% at a cut off risk of 1 in 300 or higher. However, there is considerable disagreement in the literature as to the precise Down's syndrome detection rate that can be expected with this form of sonography. Cystic hygroma I s caused by the malformation of the fetal lymphatic system and is found commonly in fetuses with Monosomy X (Turner syndrome), and other chromosomal anomalies. An important part of evaluation of nuchal membrane is the evaluation of the subtle signs of hydrops fetalis. Even in the presence of a normal karyotype, perinatal outcome is very poor in the presence of fetal hydrops. Choroid plexus cyst (s) Vast majority of cyst (s) is benign and usually disappears by 24-25 weeks. However, these cysts may be associated with chromosomal anomalies, primarily trisomy 18 but occasionally trisomy 21. Choroid plexus cysts have been reported to be associated with trisomy 18 in 1% to 6 % cases. For isolated choroid plexus cysts, the risk for trisomy 18 and trisomy 21 is about 1.5 times the background. Intracardiac echogenic foci Increased echogenicity (golf ball) located in chordae tendinae is seen in 3 to 5 % of fetuses and is considered by most investigators of no pathological significance. However, they are sometimes associated with chromosomal abnormalities particularly, trisomy 21. For isolated hyperechogenic foci the risk for trisomy 21 may be four times the background. Hyperechogenic fetal bowel Hyperechogenic bowel has been described as a normal variant, but may also be associated with cystic fibrosis, meconium peritonitis, cytomegalovirus infection or trisomy 21. For isolated hyperechogenic bowel, the risk for trisomy 21 may be three times the background. Mild hydronephrosis Minimal pyelectasis in the fetus is common and unlikely to be significant in every case. However, UPJ obstruction and reflux may manifest initially as mild fetal pyelectasis. In addition, karyotype abnormalities, remarkably trisomy 21, are reported to be associated with mild pyelectasis. Long bone biometry Short humeri and short femurs may be found in fetuses with Down's syndrome. Measurements are usually compared with BPD rather than menstrual age due to the uncertainty of the menstrual history. If the femur length is below 5th centile and all other measurements are normal, the fetus is likely to be normal but rather short. However, this finding is rarely related to dwarfism and occasionally trisomy 21. Fetal hand Abnormalities of fetal hand such as polydactyly, over-riding fingers, or abnormal hand positioning, especially if associated with polyhydramnios, have been reported to be associated with fetal chromosomal abnormalities. Club foot / Rocker bottom feet (positional deformities) Club foot has been associated with a variety of chromosomal abnormalities, especially trisomy 13 and 18. Whether or not infants with isolated club foot are at significantly increased risk of chromosomal abnormalities is still unresolved. Rocker bottom feet are also a feature of trisomy 13 and 18. The finding of this deformity should be a stimulus to detailed fetal examination and fetal karyotyping. Single umbilical artery A single umbilical artery is found in 0.5% to 2% of newborns and is associated with structural or other anomalies in 20% to 50% of cases; usually relatively minor anomalies of the renal or genital tracts. Whether or not the presence of an isolated single umbilical artery is an indication for genetic studies is still uncertain. Intrauterine growth restriction A significant percentage of fetuses with chromosomal abnormalities are growth restricted. Some investigators have suggested the presence of IUGR alone is an indication for genetic studies. Many additional abnormalities such as cerebellar hypoplasia, isolated pericardial effusion, sandal-foot, reduction defect of forearm, low set ears or shortened ear length, fetal cholecystomegaly, and polyhydramnios have been found to be associated with chromosomal anomalies. When these findings are seen in isolation, it is still controversial whether or not amniocentesis should be offered. The sensitivity of ultrasonography for detection of fetal trisomic conditions varies with the type of chromosome abnormality, gestational age at the time of sonography, reasons for referral, criteria for positive sonographic findings, and the quality of the sonography. As an estimate, 1 or more sonographic findings can be identified in approximately 90% of fetuses with trisomy 13, 80% of fetuses with trisomy 18, and 50 % to 70% of fetuses with trisomy 21. Clusters of minor sonographic markers greatly increase the likelihood of karyotypic abnormality compared with a single minor marker . Cardiovascular anomalies Since malformations of the heart are the most common birth defect in fetuses with serious chromosomal abnormalities, color Doppler ultrasound evaluation of the cardiovascular system can be used to improve the detection rate of these abnormalities. By the inclusion of color Doppler sonography in genetic ultrasound, 96% of fetuses with Down's syndrome, 98% of all trisomies, and 88 % of all chromosomal abnormalities can be detected . A complete normal ultrasound examination result reduces the risk of abnormal karyotype,by,62%. 2.Biochemical,tests A large number of serum analytes have been found to be associated with chromosomal abnormalities. Various principal biochemical analytes currently available for the prenatal screening of chromosomal abnormalities during first and second-trimester of pregnancy are; pregnancy associated plasma protein-A (PAPP-A), maternal serum alpha-feto-protein (MSAFP), free-beta hCG, total hCG, unconjugated estriol (uE3), and inhibin-A. PAPP-A and free-beta hCG are only biochemical markers identified to be of value in first-trimester screening. Free-beta hCG is the only marker that is effective in both the first and second-trimester pregnancy. PAPP-A It is a homotetrameric glycoprotein (metzincins family of metalloproteases) which is synthesized in chorionic villi [35]. It can be measured in maternal serum; its concentration increases rapidly after 7th week of pregnancy and its potential clinical usefulness is greatest in the first trimester (10th to 14th week of gestation). When the fetus is affected with trisomy 21, PAPP-A levels are decreased by more than half [36]. Low PAPP-A is also associated with trisomy 18 and 13. Using PAPP-A alone, detection rate of Down's syndrome is about 40%. When PAPP-A was combined with maternal age, the detection rate increased to 50% with a 5% screen-positive rate [37]. Decreased production of PAPP-A may cause intrauterine growth restriction [38] as this hormone control the level of insulin -like growth factors (IGF) in the placenta. MSAFP MSAFP is a glycoprotein produced by the fetal yolk sac and fetal liver. Fetal plasma concentration increases to a maximum (approximately 3.0-4.0 g/L) between 13-14 weeks of gestation. Maternal serum levels peak at about 30 weeks (about 250 mg/L). After birth, maternal and infant AFP rapidly declines. High MSAFP levels may occur in the following conditions; 1. Underestimated gestational age 2. Multiple gestation. 3. Neural tube defects (anencephaly, spina bifida, encephalocele). 3 Abdominal wall defects (omphalocele, gastroschisis) 4. Various other fetal abnormalities such as hydrocephaly, microcephaly, cystic hygroma, cyclopia, tetralogy of Fallot, duodenal atresia, congenital nephropathies, sacrococcygeal teratoma, hydrops fetalis and Turner's syndrome without hygroma. 5. Complications of pregnancy ( fetal distress, growth retardation, early intrauterine death, placental defects, abdominal pregnancy, and maternal proteinuric preeclampsia). 6. Congenital fetal neoplasms, and maternal AFP producing neoplasms. Low MSAFP levels may be associated with 1. Incorrect pregnancy dating (less advanced than originally thought). 2. Complications of pregnancy (missed abortion, spontaneous abortion, late fetal death, molar pregnancy, choriocarcinoma). 3. Some normal pregnancies. 4. Large-for-dates. Very low MSAFP predicts an unusually high rate of large birth weight infants, with increased fetal, intrapartum, and neonatal consequenses. 5. MSAFP less than the median may indicate an increased risk of chromosomal abnormalities such as trisomy 21 and trisomy 18. The level of MSAFP in Down's syndrome pregnancies are about 72% of the normal values for weeks 14 to 21. Using maternal age and MSAFP level, the detection rate of Down's syndrome pregnancies is about 25-33%, at a false positive rate of 5% . Total hCG hCG is a dimeric glycoprotein composed of two non-covalently linked polypeptide sub-units, alpha and beta. It is first secreted by the fertilized ovum and later by placental tissue. Serum hCG levels increase exponentially between 3-10 weeks of pregnancy. Levels reach a peak during the first-trimester (about 100000 m IU/ml) and decline during the second and third-trimesters. In normal second-trimester maternal sera, the level of intact hCG ranges from 20,000-50,000 mIU/ml. In trisomy 21 pregnancies, second -trimester hCG levels are elevated varying from 2.04 to 2.5 MoM or greater while in trisomy 18 and 13, hCG levels are lower than normal. Using maternal age and hCG levels, Down's syndrome detection rate is about 60 % at a false positive rate of 6.7 % . Very high levels of hCG suggest trophoblastic disease. Various workers found a significant increase in the levels of free beta-hCG in trisomy 21, and concluded that this biochemical analyte is superior to intact hCG for the detection of trisomy 21. The levels of this analyte are reduced in the blood of women carrying fetuses with trisomy 18 . Unconjugated estriol (uE3) The substrate for estriol begins as dehydroepiandrosterone (DHEA) made by the fetal adrenal glands. This is later hydroxylated in fetal liver and cleaved by steroid sulphatase in placenta where unconjugated fraction converts to uE3. The amount of estriol in maternal serum is dependent upon a viable fetus, a properly functioning placenta, and maternal wellbeing. In normal pregnancies, uE3 levels increase from about 4 nmol/L at 15 weeks gestation to about 40 nmol/L at delivery. uE3 tends to be lower when trisomy 21or 18 is present and when there is adrenal hypoplasia with anencephaly. Second-trimester maternal serum uE3 levels in Down's syndrome pregnancies are approximated 75% of the values expected in normal pregnancies . Using maternal age and uE3 levels detection rate of about 45.7% at a false positive rate of 9.1 % was found . Inhibin-A Inhibin-A is a heterodimeric glycoprotein of placental origin similar to hCG. Inhibin-A levels in maternal serum are relatively constant through the 15th-18th week of pregnancy. Maternal serum levels of inhibin-A are twice as high in pregnancies affected by Down's syndrome as in unaffected pregnancies while in trisomy 18, inhibin-A levels are lower than normal. Inhibin-A is used with three other analytes (MSAFP, hCG, uE3) and maternal age to characterize more accurately Down's syndrome risk, and a reduction of the false positive rate was detected. Currently available evidences suggest that sensitivity of individual maternal serum markers is substantially low. To improve the sensitivity and specificity of biochemical markers, various combinations of 2, 3, or 4 analytes are offered during first and / or second-trimester screening. Various combinations of analytes include; 1. First-trimester maternal serum double test using PAPP-A and free-beta hCG. This is vastly more effective than any other screening program and is of great advantage because it is available in the first-trimester. The disadvantage is that the test will not detect neural tube defects, so a MSAFP test will still need to be done. After combining PAPP-A and free beta-hCG with maternal age, detection rate of aneuploidy is about 60% at a 5% screen-positive rate. 2. Second-trimester screening includes; double test (MSAFP+ free-beta hCG or total hCG), triple test (MSAFP+hCG+uE3), and quad screen test (MSAFP+hCG+uE3+inhibin-A). When an ultrasound scan is used to estimate gestational age the Down's syndrome detection rate for a 5% false positive rate is estimated to be 59% using the double test (AFP and hCG), 69% using the triple test (AFP,hCG,uE3), and 76% using the quad test (AFP,hCG,uE3, inhibin-A), all in combination with maternal age. Main disadvantage of second-trimester screening is the timing of the test. By the time a definitive diagnosis is made via amniocentesis (after a positive screen result), the option of termination of pregnancy can be difficult. MSAFP is always included as a component of second-trimester biochemical screening because this analyte is widely used for the detection of ONTDs at this stage of pregnancy. Addition of uE3 as an analyte for prenatal screening is controversial. Some authors pointed out that inclusion of this analyte does not improve detection rates, where as in another study a fall in detection rate was noticed. On the other hand, some workers rely on the usefulness of uE3 as a serum marker. In a study, it was found that double test is not worse than the triple test and the double test is preferred because of lower running cost. Comparing free beta-hCG and total hCG, it was found that free beta hCG is better option because it improves the Down's syndrome detection efficiency by 10 % over total hCG at a lower false positive rate. Review of the literature suggests that the combined use of free beta-hCG and AFP instead of total hCG, AFP and uE3, is better screening test because it is more effective, less expensive, and is not limited to 16-20 weeks gestation. The addition of uE3 and inhibin-A adds no significant advantage to the double test. However, some workers recommend triple test while some rely on quad test for better results. Combined screening Since maternal biochemical and sonographic markers are largely independent, combined risk estimate results in even higher detection rate than either alone. Thus combination of a multiple marker test (PAPP-A and free b-hCG) and an ultrasound at 11 to 14 weeks which is targeted to look NT, and maternal age gives a detectable rate of aneuploidy of about 90 % with an invasive testing rate of about 5%. But in many high-risk situations this may still leave the patient at risk. Integrated screening The integrated test includes measurements of PAPP-A and NT in the first-trimester and measurements of MSAFP, uE3, hCG, and inhibin-A in the second-trimester. The integrated test can achieve a high detection rate with a much lower false positive rate (0.9%) than screening based on markers measured in either trimester alone. Consequently the need for amniocentesis or CVS is reduced by four fifths, with a similar reduction in the loss of unaffected fetuses. The estimates of the integrated test's performance are based on there being little or no correlation between the first and second-trimester markers used with the exception of free beta-hCG and total hCG. Disadvantage of the test is that it is expensive, and option of making the diagnosis in the first-trimester is eliminated. Recently, Azuma M, et al used Lens culinaris agglutinin reactive alpha-fetoprotein ratio for the detection of fetal Down's syndrome in combination with traditional serum markers such as AFP, hCG and uE3 and found a detection rate of 83.9% with a 5.1% false positive rate. Various factors affect the accuracy of biochemical tests. Therefore, adjustments are made to take account of these factors when categorizing the result as screen positive or screen negative. These factors are: 1. Gestational age: Measured concentrations of the serum markers vary with gestational age, Between 9 to 14 weeks, maternal serum free beta-hCG decreases, median free beta-hCG also decreases while median PAPP-A increases. Between 14-22 weeks, Median MSAFP and median uE3 increases, median hCG decreases while median inhibin-A is less affected. 2. Maternal weight: Maternal weight has a significant effect on the screening process. There is inverse correlation between body weight and concentration of biochemical markers. If the volume of distribution is greater, the concentration of AFP will be smaller. Maternal weight also has a significant inverse correlation on inhibin-A levels. PAPP-A and free beta-hCG also show a small but significant negative correlation. But there is no correlation for uE3. 3. Smoking: Maternal smoking has a small effect on overall screening performances. Women who smoke are more likely to produce a small amount of PAPP-A. 4. Effect of parity: Parity significantly affects the mean MoM of hCG but did not affect the values for uE3 or MSAFP. 5. Multiple pregnancies: On an average, the levels of MSAFP and free beta-hCG were twice as high in twins and over three times as high in triplets. 6. Difference between races of ethnic groups: Medians are significantly different in races of ethnic groups. Black women, on an average, have higher levels of MSAFP than Caucasian, Asian or Hispanic women. 7. Insulin-dependent diabetes mellitus: MSAFP levels in IDDM have shown an approximately 20% decrement while uE3 and inhibin-A levels are reduced to a smaller extent . Conclusions of multiple marker screening test: 1. Maternal blood screening is originally developed for pregnant women who are at a 'low-risk' for disorders being screened. However, in certain situations maternal serum marker screening can be assayed in women > or =35 years.. 2. Gestational age must be accurately known. First-trimester screening is offered between 10 to 14 weeks of gestation, while second-trimester screening tests are given between 14 and 22 weeks of pregnancy, with 16 to 18 weeks (when the hormone levels are most consistent) being the optimum time. Recently Muller F, et al assessed the diagnostic value of maternal serum marker screening at 18-35 weeks and concluded that biochemical screening is feasible at 18 weeks and later, which may be of interest in selected cases. 3. Multiple gestation screening is not as sensitive as singleton screening with biochemical analysis. 4. Screening utilizing biochemical test, NT and maternal age mainly identifies aneuploidy and some other chromosomal abnormalities only and therefore shall miss majority of other non-Down, non-trisomy 18 chromosome abnormalities, nor does it identify other physical or mental birth defects. 5. A low PAPP-A, low MSAFP, low uE3, and high free beta-hCG, and high inhibin-A levels are associated with higher risk for Down's syndrome while low levels of all hormones suggest an increased risk for trisomy 18. In trisomy 13, PAPP-A and free beta-hCG levels are low but detection rate using second-trimester analytes is poor. 6. Although screening protocol has a 90 % pickup rate of aneuploidy, it is not diagnostic. Hence, suspicious screening results will tell of an increased risk of a problem, but not diagnose the problem as being present or being absent. Therefore, a negative screening result may falsely reassure many women who are carrying an affected fetus. Conversely, a false positive result may culminate in termination of a normal pregnancy. The main aim of screening test is to identify a group of women at significantly high-risk of having an affected child to justify the offer of a diagnostic test. 3. Non-invasive screening using fetal blood cells and fetal DNA. (a)Fetal blood cells: The fetal and maternal circulations are separated by the placental membranes, but this barrier is incomplete to cellular trafficking. Bi-directionality and bimodality (cell and cell-free DNA) of fetomaternal trafficking is an established fact. Fetal nucleated cells such as trophoblasts, erythrocytes and white blood cells are found in maternal blood, and have been widely pursued as potential substrates for noninvasive prenatal diagnosis. However, concentration of these cells in maternal blood is very low (1fetal cell in 103-108 maternal cells) and therefore isolation of these cells for cytogenetic analysis requires expensive euipments and great expertise. Isolation of erythroblasts has attracted most attention because they are abundant in early fetal blood, they are extremely rare in normal adult blood and their half-life in adult blood is only about 30 days. Relatively specific monoclonal anibodies against these cells are also available. Trophoblastic cells and white cells are not used for prenatal screening because trophoblastic cells are cleared by maternal lungs whereas half life of the white cells is very long which may lead to contamination from previous pregnancies. A combination of sophisticated physical and immunological methods are used for the identification, isolation and enrichment of different types of fetal blood cells from maternal blood obtained at 12-16 weeks of gestation. Physical methods include triple density gradient centrifugation and micromanipulation techniques while immunological methods include the use of magnetically labelled or fluorescent monoclonal antibodies such as anti-CD71 (transfferin receptor). Commonly used immunological methods are, magnetic cell sorting (MACS) or fluorescence activated cell sorting (FACS). By these methods the fetal cells can be enriched to about 1 in 10-100 materanl cells. Enriched cells are used for the detection of specific chromosomes by fluorescent in situ hybridization (FISH) and for the analysis of fetal genetic loci by single cell PCR. FISH involves the hybridization of DNA probes representing a specific chromosome or chromosomal region to target DNA such as metaphase chromosomes or interphase nuclei. Fetal trisomy is suspected if some of the enriched cells show three-signal nuclei rather than the normal two. Over the past decade, progress has been made towards the isolation and analysis of fetal blood cells from maternal blood, using various enrichment strategies and analysis by fluorescent in situ hybridization with choromosome-specific probes and PCR. It is now possible to identify simultaneously all major chromosomal abnormalities by the use of multicolor probes directed against chromosomes 21,18,13,Y and X in interphase nuclei. Another method that is currently being explored involves culturing fetal blood cells. The sensitivity for detecting aneuploidy using fetal cells is competitive with first or second-trimester maternal serum screening with the advantage that the invasive testing rate may be as low as 0% rather than 5%. But the current technology precludes application of this concept for mass population. However, fetal cells might be analyzed only after a positive serum or ultrasound finding. If fetal aneuploid cells are not recovered, an invasive diagnostic procedure could be avoided. (b) Fetal DNA Isolation of fetal cells from the cellular fraction of maternal blood needs expensive and advance equipment because of the rarity of such cells. Recently, there has been much interest in the use of the non-cellular portion of blood, namely plasma, for molecular analysis diagnosis. Fetal DNA has been identified in the plasma of pregnant women at concentrations much higher than those present in the cellular fraction. Until recently, it was assumed that fetal DNA detected in maternal plasma was cell free and a definitive diagnosis of fetal chromosomal aneuploidies was not thought possible. Studies now indicate that some fetal DNA originates from intact fetal cells. Trophoblasts may be the predominant cell population involved in the liberation of fetal DNA into the cell-free fraction. It was found that the absolute concentration of fetal DNA in maternal serum increases with gestational age, with a sharp rise near the end of the pregnancy. Fetal DNA is cleared rapidly from maternal blood after delivery with a half-life of minutes. Increase in fetal DNA in maternal plasma has been noticed in pregnancies affected by fetal trisomy, and in premature labour, and preeclampsia. Using fetal DNA in maternal plasma for the screening of fetal chromosome aneuploidies is possible, especially in conjugation with other established serum markers. The median fetal DNA concentration in Down's syndrome cases was found to be 1.7 times higher than in controls. Second-trimester cell-free fetal DNA estimation gave a 21% detection rate at a 5% false-positive rate. When added to quadruple marker screening, fetal DNA estimation modestly increased the screening performance above what is currently available in the second-trimester. The relative ease and reliability with which fetal DNA can be detected have thus opened new possibilities for non-invasive prenatal diagnosis. Invasive diagnostic procedures 1.Chorionic villus sampling CVS is a prenatal test that involves taking a sample of some of the placental tissue. Main complications of CVS include severe transverse limb defects and oromandibular-limb hypogenesis [103]. Possible mechanism of severe transverse limb abnormalities is hypoperfusion, embolization and release of vasoactive substances due to trauma during the procedure. There is strong association between the severity of the defect and the gestation at sampling. Decreasing risk and a trend from proximal to distal limb damage with increasing gestational age at CVS provide biologic plausibility for a true association with limb reduction defects [104,105]. CVS as early as 8 weeks of gestation may lead to amputation of whole limb while sampling at 10 weeks only affects terminal phalanxes. Thus, to avoid severe limb defects, CVS prior to 11 weeks of gestation should be discouraged. The increase in the miscarriage rate following this procedure is about 0.5% above the background risk for miscarriage, which is 2-3% at 10-12 weeks of pregnancy. Various trials compared CVS in first-trimester and amniocentesis in the second-trimester and concluded that both procedures are equally effective and safe with similar rates of procedure-induced fetal loss at experienced centers. The main advantage of CVS over amniocentesis is that prenatal diagnosis is achieved during the first-trimester, which allows a couple the opportunities to consider their options earlier in the pregnancy in the event of an abnormal result. However, screening for ONTDs cannot be achieved through CVS. The main indication for repeat CVS is mosaicism. 2.Amniocentesis Amniocentesis was first used for prenatal diagnosis in the 1950's and the feasibility of culturing and karyotyping amniotic fluid cells was first demonstrated in the late 1960s. Although the exact risk associated with amniocentesis is controversial, it is also not a completely innocuous procedure and can result in various complications such as spontaneous abortion, premature labour, placental abruption, intrauterine death and neonatal death. Other reported procedure-related complications include increased risk of respiratory distress syndrome and pneumonia in neonates, talipes and dislocation of the hip, postprocedural amniotic fluid leakage of amniotic fluid, vaginal bleeding, chorioamnionitis, amniotic band formation and rare needle puncture of the fetus. Amniocentesis may results in future reproductive complications secondary to sensitization to Rh and other rare antigens such as Kell. Amniocentesis can be performed as early as 11-13 weeks of gestation. But at this stage of pregnancy, the procedure is not only technically difficult to perform, it is also associated with increased incidence of total fetal loss, talipes equinovarus and post-procedural amniotic fluid leakage. Incidence of failed culture is also high in early amniocentesis. Thus, the procedure should not be performed before 13 weeks gestation unless there are special circumstances. Potential advantage associated with amniocentesis includes; 1.The amniotic fluid can be tested to measure the amount of AFP, which is a diagnostic test for detecting ONTDs 2. Possibility of an abnormal chromosome result due to chromosomal mosaicism confined to the placenta is reduced.