USMLE Step 2 Secrets- OB
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A patient who is taking birth control pills presents with amenorrhea. What is the likely cause?
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Pregnancy. No form of contraception is 100% effective (including tubal ligation), especially when patient compliance is required.
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List the symptoms and signs of pregnancy.
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1) Amenorrhea. 2) Morning sickness. 3) Weight gain. 4) Hegar sign (softening and compressibility of the lower uterine segment). 5) Chadwick sign (dark discoloration of the vulva and vaginal walls). 6) Linea nigra. 7) Melasma (also known as chloasma or the \"mask of pregnancy\"). 8) Auscultation of fetal heart tones. 9) Gestational sac or fetus seen on ultrasound. 10) Uterine contractions. 11) Palpation/ballottement of fetus.
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Which vitamin should all pregnant women take? Why?
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Give all pregnant patients folate to prevent neural tube defects. Ideally, all women of reproductive age should take folate because it is most effective in the first trimester, before most women know that they are pregnant. Iron supplements frequently are given to pregnant women to help prevent anemia.
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Define macrosomia. What is the likely cause?
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Macrosomia is defined as a newborn that weighs more than 4 kg (roughly 9 lb). The cause is maternal diabetes mellitus until proven otherwise.
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What routine tests should be obtained for all pregnant patients? **AT FIRST VISIT**
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Blood type, rhesus (Rh) type, and antibody screen: At first visit (for identification of possible isoimmunization). Urinalysis: At the first visit and every visit thereafter (to screen for proteinuria, preeclampsia, and bacteriuria; not a good screen for diabetes). Hemoglobin and hematocrit: At the first visit to determine whether the patient is anemic (because pregnancy may worsen anemia); repeat in the third trimester. Syphilis test: At first visit (mandated in most states) and subsequent visits (for high-risk patients). Glucose screen for gestational diabetes: At first visit in patients with risk factors for diabetes mellitus (obesity, positive family history, or age older than 30 years); otherwise, screen at 24 to 28 weeks. Use fasting serum glucose and serum glucose levels 1 or 2 hours after an oral glucose load (oral glucose tolerance test).
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What routine tests should be obtained for all pregnant patients? **Subsequent Visits**
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Pap smear: If the patient is due for a pap smear. Pregnancy does not change the frequency of screening. Urine culture: Obtained at 12 to 16 weeks to screen for asymptomatic bacteriuria. Rubella antibody screen: If the patient is found to be nonimmune, counsel her to get postpartum immunization. Rubella vaccine should not be given during pregnancy. Serum alpha-fetoprotein: Performed at 15 to 20 weeks, primarily to detect open spina bifida and anencephaly.
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What routine tests should be obtained for all pregnant patients? **Subsequent Visits** continued...
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Hepatitis B antigen testing: To prevent perinatal transmission. Varicella: All pregnant women should be tested for immunity to varicella. Thyroid function: Maternal hypothyroidism may affect fetal neurologic development. Maternal hyperthyroidism can lead to fetal and maternal complications. HIV test: The American College of Obstetrics and Gynecology (ACOG) advocates an \"opt-out\" approach to screening rather than an \"opt-in\" approach to increase screening. Chlamydia screening: The Centers for Disease Control and Prevention (CDC) and ACOG advocate testing all pregnant women at the first prenatal visit. Down syndrome screening: Should be offered to all pregnant patients. There are multiple ways to screen. Group B beta-hemolytic streptococcus (GBS): Screen at 35 to 37 weeks with a swab of the lower vagina and rectum. Others: Tuberculosis skin test for women at higher risk. Testing for gonorrhea for women at higher risk of infection. Testing for toxoplasmosis is controversial. If asked, you should do chlamydia and gonorrhea cultures for any pregnant teenager. Testing for sexually transmitted infections should be repeated in the third trimester for women who continue to be at risk or for women who acquire a risk factor during pregnancy.
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On every prenatal visit, listen to fetal heart tones and evaluate uterine size. When can these factors first be noticed? What constitutes a size/date discrepancy?
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Fetal heart tones can be heard with Doppler ultrasound at 10 to 12 weeks and with a normal stethoscope at 16 to 20 weeks. At 12 weeks of gestation, the uterus enters the abdomen and is palpable at the symphysis pubis; at roughly 20 weeks, it reaches the umbilicus. Uterine size is evaluated by measuring the distance from the symphysis pubis to the top of the fundus in centimeters. At roughly 20 to 35 weeks, the measurement in centimeters should equal the number of weeks of gestation. A discrepancy greater than 2 to 3 cm is called a size/date discrepancy. Ultrasound should be done for further evaluation (e.g., intrauterine growth retardation, multiple gestations).
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When is ultrasound most accurate at estimating the fetal age?
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At 16 to 20 weeks, the biparietal diameter (measured on ultrasound) gives the most accurate estimate of fetal age.
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What is a hydatiform mole?
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A hydatiform mole is one form of gestational trophoblastic neoplasia, in which the products of conception basically become a tumor.
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What are the clues to its presence of hydatiform mole?
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1) Preeclampsia before the third trimester. 2) An hCG level that does not return to zero after delivery (or abortion/miscarriage) or one that rises rapidly during pregnancy. 3) First- or second-trimester bleeding with possible expulsion of \"grapes\" from the vagina (grossly, the tumor looks like a \"bunch of grapes\") and excessive nausea/hyperemesis. 4) Uterine size/date discrepancy. 5) \"Snowstorm\" pattern on ultrasound.
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How are hydatiform moles treated?
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Treat hydatiform moles with uterine dilation and curettage. Then follow with serial measurements of hCG levels until they fall to zero. If the hCG level does not fall to zero or rises, the patient has either an invasive mole or a choriocarcinoma (increasingly aggressive forms of gestational trophoblastic neoplasia) and needs chemotherapy (usually methotrexate or dactinomycin, both of which are extremely effective).
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Distinguish between complete and partial moles.
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Complete moles have a karyotype of 46 XX (with all chromosomes from the father) and no fetal tissue. Incomplete moles usually have a karyotype of 69 XXY with fetal tissue in the tumor.
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How is intrauterine growth retardation (IUGR) defined? What causes it?
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1) IUGR is defined as fetal size below the tenth percentile for age. 2) Causes are best understood in broad terms as maternal (e.g., smoking, alcohol or drug use, lupus erythematosus), fetal (e.g., TORCH infections, congenital anomalies), or placental (e.g., hypertension, preeclampsia).
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When should ultrasound be used to evaluate the fetus?
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Order ultrasound for all patients who have a size/date discrepancy greater than 2 to 3 cm or risk factors for pregnancy-related problems (e.g., hypertension, diabetes, renal disease, lupus erythematosus, smoking, alcohol or drug use, history of previous pregnancy-related problems). Ultrasound also is used when fetal death, distress, or abortion or miscarriage is suspected (e.g., a baby that stops kicking, vaginal bleeding, slow fetal heartbeat on auscultation).
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How is fetal well-being evaluated?
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1) A nonstress test is the easiest initial screen. It is performed with the mother at rest. A fetal heart rate tracing is obtained for 20 minutes. A normal strip has at least 2 accelerations of heart rate, each at least 15 beats per minute above baseline and lasting at least 15 seconds. 2) A biophysical profile is slightly more involved and includes a nonstress test as well as a measure of amniotic fluid (to determine whether oligohydramnios or polyhydramnios is present), a measure of fetal breathing movements, and a measure of general fetal movements. 3) If the fetus scores poorly on the Biophysical Profile, the next test is the Contraction Stress Test, which looks for uteroplacental dysfunction. Oxytocin is given, and a fetal heart strip is monitored. If late decelerations are seen on the fetal heart strip with each contraction, the test is positive. In most cases of a positive contraction stress test, a cesarean section is performed.
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True or false: A biophysical profile often is used in high-risk pregnancies in the absence of obvious problems.
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True. A biophysical profile may be done once or twice a week from the start of the third trimester until delivery to monitor for potential problems.
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True or false: Aspirin should be avoided during pregnancy.
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True. Use acetaminophen instead. One important exception is in patients with antiphospholipid syndrome, in whom aspirin may improve pregnancy outcome (subcutaneous unfractionated heparin or low molecular weight heparin also can be used to treat antiphospholipid syndrome in pregnancy).
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Define postterm pregnancy
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Postterm pregnancy is defined as more than 42 weeks of gestation.
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Why is postterm pregnancy a major concern?
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Both prematurity and postmaturity increase perinatal morbidity and mortality rates. With postmaturity, dystocia (or difficult delivery) becomes more common because of the increased size of the infant.
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How is postterm pregnancy treated?
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In general, if the gestational age is known to be accurate and the cervix is favorable, labor is induced (e.g., with oxytocin). If the cervix is not favorable or the dates are uncertain, twice-weekly biophysical profiles are done. At 41 weeks, most obstetricians advise induction of labor.
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What two rare disorders are associated with prolonged gestation?
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Anencephaly and placental sulfatase deficiency.
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What are the normal changes and complaints in pregnancy?
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Normal changes in pregnancy include nausea or vomiting (morning sickness), amenorrhea, heavy (possibly even painful) feeling of the breasts, increased pigmentation of the nipples and areolae, Montgomery tubercles (sebaceous glands in the areola), backache, linea nigra, melasma (chloasma), striae gravidarum, and mild ankle edema. Heartburn and increased frequency of urination are also common problems.
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What test is used to screen for neural tube defects? At what time during pregnancy is it measured? Explain the significance of a low or high alphafetoprotein (AFP) level in maternal serum.
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1) Maternal AFP is most accurate when measured between 15 and 20 weeks of gestation. 2) A low AFP may represent Down syndrome, fetal demise, or inaccurate dates. A high AFP may represent neural tube defects (e.g., anencephaly, spina bifida), ventral wall defects (e.g., omphalocele, gastroschisis), multiple gestation, or inaccurate dates.
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What should be done if the AFP is elevated?
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Repeat the test. As many as 30% of elevated maternal serum AFP test results may be elevated but are normal upon repeat testing. The initial elevation is not associated with an increased risk of neural tube defects.
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What further testing should a patient undergo if the AFP remains elevated?
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If the AFP remains elevated, the patient is advised first to undergo ultrasound to determine whether a neural tube defect or other anomaly is present. The ultrasound is also used to confirm gestational age, number of fetuses, and fetal viability. Further evaluation with amniocentesis may be required if the ultrasound findings are uncertain or there is a concern for nonvisualized neural tube defects (via elevated AFP level in amniotic fluid or detection of acetylcholinesterase in amniotic fluid). There is a small risk of miscarriage after amniocentesis.
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What prenatal tests are available to screen for Down syndrome?
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The first trimester combined test, integrated tests, sequential testing, contingent testing, the quadruple test, and maternal plasma-based tests. The ACOG recommends that all women be offered screening before 20 weeks of gestation.
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What is the first trimester combined test? When is it performed?
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The first trimester combined test is performed at 11 to 13 weeks of gestation. The test involves determination of nuchal translucency (NT) by ultrasound, combined with serum pregnancy-associated plasma protein-A (PAPP-A) and serum human chorionic gonadotropin (hCG). Chorionic villus sampling (CVS) is used for women who have this first trimester screening and test positive.
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Describe the integrated tests.
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The full integrated test includes an ultrasound measurement of nuchal translucency at 10 to 13 weeks of gestation, PAPP-A at 10 to 13 weeks of gestation, and AFP, unconjugated estradiol (uE3), hCG, and inhibin A at 15 to 18 weeks of gestation. Results of the full integrated test are not available until the second trimester. The serum integrated test is the same as the full integrated test but without the ultrasound evaluation of nuchal translucency. This test is used in areas where expertise in the ultrasound measurement of nuchal translucency is not available. Results of the serum integrated test are not available until the second trimester.
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Describe sequential testing.
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Step-wise sequential testing has been developed to provide a risk estimate during the first trimester. The first trimester portion of the integrated screen is performed. If the tests indicate a very high risk of having an affected fetus, CVS is offered. Those women whose results do not place them at very high risk of having an affected fetus go on to have the second trimester portion of the screening.
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What is the quadruple test? For whom is it typically used? When is it performed?
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The quadruple test includes the serum markers AFP, uE3, hCG, and inhibin A. The quadruple test is the best available test for women who receive prenatal care in the second trimester, but can be used for women who receive earlier prenatal care. It is performed at 15 to 18 weeks of gestation.
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What is a maternal plasma-based test?
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Also called cell-free fetal DNA testing, detects fetal DNA in the circulation and has a detection rate more than 98% and a false-positive rate of less than 0.5% for Down syndrome and Edward syndrome (trisomy 18). It is used after 10 weeks of gestation. Cell-free fetal DNA testing is not yet validated in low-risk women, but can be used in higher risk women (i.e., women who will be older than 35 at the time of delivery; presence of sonographic findings associated with fetal aneuploidy; history of previous pregnancy with fetal trisomy; or positive screening results on tests such as the first trimester combined test, the integrated test, or the quadruple test).
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What is the next step if a woman has a positive screening test for Down syndrome?
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Offer fetal karyotype determination. This is done by CVS in the first trimester and by amniocentesis in the second trimester.
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Why is CVS done instead of amniocentesis in some cases?
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CVS can be done at 9 to 12 weeks of gestation (earlier than amniocentesis) and generally is reserved for women with previously affected offspring or known genetic disease. It offers the advantage of a first-trimester abortion if the fetus is affected. CVS is associated with a slightly higher miscarriage rate than amniocentesis.
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True or false: CVS can detect neural tube defects but not genetic disorders
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False. CVS can detect genetic or chromosomal disorders but not neural tube defects.
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List the teratogenic effects of maternal diabetes mellitus. What is the best way to reduce these complications?
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1) Cardiovascular malformations 2) Cleft lip and/or palate 3) Caudal regression (lower half of the body is incompletely formed) 4) Neural tube defects 5) Left colon hypoplasia/immaturity 6) Macrosomia (most common and classic) 7) Microsomia (can occur if the mother has long-standing diabetes) ***Tight control of glucose during pregnancy dramatically reduces these complications***
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What other problems does maternal diabetes cause in pregnancy?
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In the mother, diabetes can result in polyhydramnios and preeclampsia (as well as the complications of diabetes). Problems in infants born to a diabetic mother (other than birth defects) include an increased risk of respiratory distress syndrome and postdelivery hypoglycemia (from fetal islet-cell hypertrophy caused by maternal and thus fetal hyperglycemia). After birth, the infant is cut off from the mother's glucose and the hyperglycemia resolves, but the infant's islet cells still overproduce insulin and cause hypoglycemia. Treat with intravenous glucose.
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True or false: Oral hypoglycemic agents should not be used during pregnancy.
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True. Use insulin to treat diabetes if diet and exercise cannot control glucose levels. Oral hypoglycemics, unlike insulin, may cross the placenta and cause fetal hypoglycemia.
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What commonly used drugs are generally considered safe in pregnancy?
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A short list of drugs that are generally safe in pregnancy includes acetaminophen, penicillins, cephalosporins, erythromycin, nitrofurantoin, histamine-2 receptor blockers, antacids, heparin, hydralazine, methyldopa, labetalol, insulin, and docusate.
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What are the TORCH syndromes? What do they cause?
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TORCH is an acronym for several maternal infections that can cross the placenta and can cause intrauterine fetal infections that may result in birth defects. Most TORCH infections can cause mental retardation, microcephaly, hydrocephalus, hepatosplenomegaly, jaundice, anemia, low birth weight, and IUGR.
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T = Toxoplasma gondii:
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Look for exposure to cats. Specific defects include intracranial calcifications and chorioretinitis.
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O = Other
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Varicella-zoster causes limb hypoplasia and scarring of the skin. Syphilis causes rhinitis, saber shins, Hutchinson teeth, interstitial keratitis, and skin lesions.
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R = Rubella
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Worst in the first trimester (some recommend abortion if the mother has rubella in the first trimester). Always check antibody status on the first visit in patients with a poor immunization history. Look for cardiovascular defects, deafness, cataracts, and microphthalmia.
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C = Cytomegalovirus
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Most common infection of the TORCH group. Look for deafness, cerebral calcifications, and microphthalmia.
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H = Herpes
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Look for vesicular skin lesions (with positive Tzanck smears) and history of maternal herpes lesions.
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True or false: With most in utero infections that can cause birth defects, obvious clues are present in the mother and/or fetus at birth.
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False. Although the USMLE probably will give clues, the mother may be asymptomatic (i.e., she may have a subclinical infection), and the infant may be asymptomatic at birth, developing only later such symptoms as learning disability, mental retardation, or autism.
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Describe therapy to reduce HIV transmission from an infected mother to the fetus. When should an infant born to an HIV-infected mother be tested?
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In untreated HIV-positive patients, HIV is transmitted to the fetus in roughly 25% of cases. When three-drug therapy is given to the mother prenatally and zidovudine is given to the infant for 6 weeks after birth, HIV transmission is reduced to roughly 2%. A noninfected infant may still have a positive HIV antibody test at birth because maternal antibodies can cross the placenta. Within 6 to 18 months, however, the test reverts to negative. This is why infants of infected mothers are tested using a direct HIV DNA PCR (polymerase chain reaction) test at birth, at 4 to 6 weeks of age, and 2 months after the second test. Babies who have these three negative tests should have an HIV antibody test at 12 and 18 months of age. Cesarean section may reduce HIV transmission to the child.
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What should you do if a pregnant woman has genital herpes?
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A decision is generally made when the mother goes into labor (not beforehand). If, at the time of true labor, the mother has active, visible genital herpes lesions, do a cesarean section to prevent transmission to the fetus. If, at the time of true labor, the mother has no visible genital herpes lesions, the child can be delivered vaginally.
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What should you do for the child if the mother has chronic hepatitis B or chickenpox?
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If the mother has chronic hepatitis B, give the infant the first hepatitis B vaccine shot and hepatitis B immunoglobulin at birth. If the mother contracts chickenpox in the last 5 days of pregnancy or the first 2 days after delivery, give the infant varicella-zoster immunoglobulin.
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How do you treat gonorrheal and chlamydial genital infections during pregnancy?
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The treatment for gonorrhea remains unchanged because ceftriaxone is safe during pregnancy. For chlamydial infection, give azithromycin, amoxicillin, or erythromycin base instead of doxycycline or erythromycin estolate.
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How is tuberculosis treated in pregnancy?
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In a similar way as for a nonpregnant patient. Use isoniazid, rifampin, and ethambutol if the risk of a drug-resistant organism is low. Pyrazinamide should be used with caution because of a lack of data on the risk of teratogenicity. However, pyrazinamide should be added if a drug-resistant organism is suspected. Streptomycin, which is a rarely used second-line agent, should be avoided. Give vitamin B6 to pregnant patients treated with isoniazid to avoid a deficiency.
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What are the signs of placental separation during delivery?
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The signs of placental separation include a fresh show of blood from the vagina, lengthening of the umbilical cord, and a rising fundus that becomes firm and globular.
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True or false: After cesarean section, a patient may have a vaginal delivery in the future.
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It depends. After a classic (vertical) uterine incision, patients must have cesarean sections for all future deliveries because of the increased rate of uterine rupture with vaginal delivery. After a lower (horizontal) uterine incision (the incision of choice), a patient may deliver future pregnancies vaginally with only a slightly increased (i.e., acceptable) risk of uterine rupture.
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Define lochia. When is it a problem?
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For the first several days after delivery, some vaginal discharge (known as lochia) is normal. It is red for the first few days and gradually turns white or yellowish-white by day 10. If the lochia is foul smelling, suspect endometritis.
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What treatment may be given to a woman who does not want to breastfeed?
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Because the breasts can become engorged with milk and thus quite painful, you may prescribe tightfitting bras, ice packs, and analgesia to reduce symptoms. Medications for the suppression of lactation (e.g., bromocriptine, estrogens, oral contraceptive pills) are generally no longer recommended because of risks of thromboembolism and stroke.
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List the common contraindications for breastfeeding.
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1) Use of alcohol or illicit drugs. 2) HIV infection,. 3) Some medications, including antineoplastic agents, antimetabolic agents (cyclophosphamide, mercaptopurine), some anticonvulsants (topiramate), amiodarone.
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What is the preferred method of anesthesia in obstetric patients? Why?
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Epidural anesthesia. General anesthesia involves a higher risk of aspiration and its resulting pneumonia because the gastroesophageal sphincter is relaxed in pregnancy and patients usually have not refrained from eating before going into labor. There also is concern about the effect of general anesthetic agents on the fetus. Spinal anesthesia can interfere with the mother's ability to push and is associated with a higher incidence of hypotension than epidural anesthesia.
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True or false: Asymptomatic bacteriuria, detected on routine urinalysis, should be treated during pregnancy.
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True. Up to 20% of patients develop cystitis or pyelonephritis if untreated. This rate is much higher than in nonpregnant patients, who should not be treated for asymptomatic bacteriuria. In pregnancy, the gravid uterus can compress the ureters, and increased progesterone can decrease the tone of the ureters, increasing urinary stasis and the risk for urinary tract infection.
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What do you need to know about vaginal group B streptococcal colonization and pregnancy?
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Pregnant women should be tested for vaginal group B streptococci. Women who are carriers should be treated during labor with penicillin G or ampicillin. Earlier treatment (e.g., second trimester) is ineffective because group B streptococci frequently return—and usually they are dangerous only during labor and delivery. The reason for treating asymptomatic carriers is to prevent neonatal sepsis and endometritis, both of which are commonly caused by group B streptococci.
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When does mastitis occur? How do you recognize and treat it?
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Mastitis (inflammation of the breast) usually develops in the first 2 months postpartum. Breasts are red, indurated, painful, and nipple cracks or fissuring may be seen. Staphylococcus aureus is the usual cause. Treat with analgesics (e.g., acetaminophen, ibuprofen), warm and/or cold compresses, and continued breastfeeding with the affected breast(s) even though it is painful (use a breast pump to empty breast if needed) to prevent further milk duct blockage and abscess formation. An antistaphylococcal antibiotic (e.g., cephalexin, dicloxacillin) is usually given for more than mild symptoms. If a fluctuant mass develops or there is no response to antibiotics within a few days, an abscess is likely present and must be drained.
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What are the diagnostic signs and symptoms of preeclampsia? When does it occur?
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Preeclampsia causes hypertension, defined as a greater than 30-point increase in systolic or a greater than 15-point increase in diastolic blood pressure over baseline. Other signs and symptoms include proteinuria (2+ or more protein on urinalysis), oliguria, edema of the hands or face, headache, visual disturbances, or the HELLP syndrome (hemolysis, elevated liver enzymes, low platelets, and right upper quadrant or epigastric pain). Preeclampsia usually occurs in the third trimester.
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What are the main risk factors for preeclampsia?
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The risk factors (in decreasing order of importance) include chronic renal disease, chronic hypertension, family history of preeclampsia, multiple gestations, nulliparity, extremes of reproductive age (the classic patient is a young woman with her first child), diabetes, and black race.
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How to treat preeclampsia?
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The definitive treatment is delivery. This is the treatment of choice if the patient is at term. In a preterm patient with mild disease, the hypertension can be treated with hydralazine, labetalol, or methyldopa. Advise bed rest and observe. If the patient has severe disease (defined as oliguria, mental status changes, headache, blurred vision, pulmonary edema, cyanosis, HELLP syndrome, blood pressure greater than 160/110 mm Hg, or progression to eclampsia [seizures]), deliver the infant once the mother's condition is stabilized. Otherwise, both mother and infant may die.
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True or false: The combination of hypertension and proteinuria during pregnancy means preeclampsia until proven otherwise.
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True
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When is edema normal during pregnancy? When is it not?
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Mild ankle edema is normal in pregnancy, but moderate-to-severe edema of the ankles or edema of the hands is likely to be preeclampsia.
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What should you consider if preeclampsia develops before the third trimester?
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The possibility of gestational trophoblastic disease (i.e., hydatiform mole, choriocarcinoma).
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Distinguish between preeclampsia and eclampsia. How can eclampsia be prevented?
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Preeclampsia plus seizures equals eclampsia. Eclampsia can be prevented by regular prenatal care so that you catch the disease in the preeclamptic stage and treat appropriately.
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What should you use to treat seizures in eclampsia? What are the toxic effects?
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Use magnesium sulfate for eclamptic seizures; it also lowers blood pressure. Toxic effects include hyporeflexia (first sign of toxicity), respiratory depression, central nervous system (CNS) depression, coma, and death. If toxicity occurs, the first step is to stop the magnesium infusion.
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True or false: When eclampsia occurs, you must deliver the infant immediately, regardless of maternal status.
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False. Do not try to deliver the infant until the mother's condition is stable (e.g., do not perform a cesarean section while the mother is having seizures).
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Why are preeclampsia and eclampsia so important?
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Preeclampsia and eclampsia cause uteroplacental insufficiency, IUGR, fetal demise, and increased maternal morbidity and mortality.
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True or false: Preeclampsia and eclampsia are risk factors for development of future hypertension.
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False
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What are the major causes of maternal mortality associated with childbirth?
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In decreasing order: pulmonary embolism (PE), pregnancy-induced hypertension (preeclampsia/ eclampsia), and hemorrhage.
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How do you recognize an amniotic fluid PE?
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Look for a recently postpartum mother who develops sudden shortness of breath, tachypnea, chest pain, hypotension, and disseminated intravascular coagulation. Treatment is supportive.
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Define oligohydramnios. What causes it? Why is it worrisome?
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Oligohydramnios means a deficiency of amniotic fluid (<500 mL or an amniotic fluid index < 5). Causes include IUGR, premature rupture of the membranes, postmaturity, and renal agenesis (Potter disease). Oligohydramnios may cause fetal problems, including pulmonary hypoplasia, cutaneous or skeletal abnormalities caused by compression, and hypoxia caused by cord compression.
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Define polyhydramnios. What causes it? Why is it worrisome?
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Polyhydramnios means an excess of amniotic fluid (>2 L or an amniotic fluid index > 25). Causes include maternal diabetes, multiple gestation, neural tube defects (anencephaly, spina bifida), gastrointestinal (GI) anomalies (omphalocele, esophageal atresia), and hydrops fetalis. Polyhydramnios can cause maternal problems, including postpartum uterine atony (with resultant postpartum hemorrhage) and maternal dyspnea (an overdistended uterus compromises pulmonary function).
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How early can a standard home pregnancy test diagnose pregnancy?
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Roughly 2 weeks after conception (about the time when the woman realizes that her period is late).
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Distinguish between a protraction disorder and an arrest disorder. What should you do when either occurs?
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A protraction disorder occurs once true labor has begun if the mother takes longer than the previous chart indicates, but labor nonetheless is progressing slowly. An arrest disorder (failure to progress) occurs once true labor has begun if no change in dilation is seen over 2 hours or no change in descent is seen over 1 hour. In either situation, first rule out an abnormal lie and cephalopelvic disproportion. If neither is present, the mother can be treated with labor augmentation (e.g., oxytocin, prostaglandin). If these steps fail, manage expectantly and do a cesarean section at the first sign of fetal distress.
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What is the most common cause of protraction or arrest disorder?
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Cephalopelvic disproportion, defined as a disparity between the size of the infant's head and the mother's pelvis. Labor augmentation is contraindicated in this setting.
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Distinguish between true labor and false labor.
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In true labor, normal contractions occur at least every 3 minutes, are fairly regular, and are associated with cervical changes (effacement and dilation). In false labor (Braxton-Hicks contractions), contractions are irregular and no cervical changes occur.
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What problems may be encountered when oxytocin is used to augment labor?
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Uterine hyperstimulation (painful, overly frequent, and poorly coordinated uterine contractions), uterine rupture, fetal heart rate decelerations, and water intoxication/ hyponatremia (because of the antidiuretic hormone effect of oxytocin). Treat all of these complications first by discontinuing the oxytocin infusion; the half-life is less than 10 minutes.
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What problems are associated with the use of intravaginal prostaglandin and amniotomy?
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Prostaglandin E2 (dinoprostone) or misoprostol may be used locally to induce the cervix (a process sometimes called \"ripening\") and is highly effective in combination with (or before) oxytocin. It also may cause uterine hyperstimulation. Amniotomy (creating a manual opening in the amniotic membrane) also hastens labor but exposes the fetus and uterine cavity to possible infection if labor does not occur promptly.
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What are the contraindications to labor induction or augmentation?
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Placenta or vasa previa, umbilical cord prolapse, prior classic (vertical) cesarean section, transverse fetal lie, active genital herpes, cephalopelvic disproportion, and cervical cancer.
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Define abortion.
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Abortion is defined as the termination (intentional or not) of a pregnancy at less than 20 weeks of gestation or when the fetus weighs less than 500 g. Miscarriage describes a spontaneous abortion.
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What are the different terms for an unintentional abortion?
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Threatened abortion: Uterine bleeding without cervical dilation and no expulsion of tissue. Treat with bed rest and pelvic rest. Inevitable abortion: Uterine bleeding with cervical dilation and crampy abdominal pain and no tissue expulsion. Incomplete abortion: Passage of some products of conception through the cervix. Complete abortion: Expulsion of all products of conception from the uterus. Treat with serial testing of hCG level to make sure that it goes down to zero. Missed abortion: Fetal death with no expulsion of tissue (in some cases not for several weeks). Treat with dilation and curettage if less than 14 weeks of gestation, attempted delivery if more than 14 weeks of gestation.
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Define induced and recurrent abortions.
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Induced abortion is an intentional termination of pregnancy at less than 20 weeks of gestation; it may be elective (requested by patient) or therapeutic (done to maintain the health of the mother). Recurrent abortion is defined as two or three successive, unplanned abortions.
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What do recurrent abortions suggest?
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1) Infection (Listeria, Mycoplasma, or Toxoplasma species, syphilis). 2)Inherited thrombophilia (factor V Leiden, G20210A gene mutation, antithrombin deficiency, deficiency of protein C or protein S). 3) Environmental factors (alcohol, tobacco, drugs). 4) Diabetes. 5) Hypothyroidism. 6) Systemic lupus erythematosus (especially with positive antiphospholipid/ lupus anticoagulant antibodies, sometimes an isolated syndrome without coexisting lupus). 7) Cervical incompetence (watch for a history of exposure to diethylstilbestrol [DES] in the patient's mother during pregnancy and/or a patient with recurrent painless second-trimester abortions; treat future pregnancies with cervical cerclage). 8) Congenital female tract abnormalities (if possible, correct to restore fertility). 9) Fibroids (remove them). 10) Chromosomal abnormalities (e.g., maternal or paternal translocations).
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True or false: hCG roughly doubles every 2 days in the first trimester.
answer
True. An hCG level that stays the same or increases only slowly with serial testing indicates a fetus in trouble (e.g., threatened abortion, ectopic pregnancy) or fetal demise. A rapidly increasing hCG level or one that does not decrease after delivery may indicate hydatiform mole or choriocarcinoma.
question
When can ultrasound detect an intrauterine gestational sac?
answer
At roughly 5 weeks after the last menstrual period (or when hCG is greater than 2000 mIU), evidence of intrauterine pregnancy can be detected by transvaginal sonography. A definite fetus and fetal heartbeat can be detected by transvaginal ultrasound at 5 to 6 weeks of gestation.
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Why do you need to know about the gestational sac?
answer
Use this information when trying to determine the possibility of an ectopic pregnancy. For example, if the patient's last menstrual period was 4 weeks ago and a pregnancy test is positive, you cannot rule out an ectopic pregnancy with ultrasound. If, however, the patient's last menstrual period was 10 weeks ago with a positive pregnancy test and an ultrasound of the uterus does not show a gestational sac, be suspicious of an ectopic pregnancy.
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What are the risk factors for developing an ectopic pregnancy?
answer
The major risk factor for ectopic pregnancy is a previous history of pelvic inflammatory disease (10-fold increase in ectopic pregnancy rate). Other risk factors include a previous ectopic pregnancy, history of tubal sterilization or tuboplasty, pregnancy that occurs with an intrauterine device in place, and a history of DES exposure, which can cause tubal abnormalities in women who were exposed in utero.
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What are the classic symptoms and signs of a ruptured ectopic pregnancy?
answer
A recent history of amenorrhea with current vaginal bleeding and abdominal pain. Patients also have a positive hCG pregnancy test. If you palpate an adnexal mass, it may be an ectopic pregnancy or a corpus luteum cyst.
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What should you do if you suspect an ectopic pregnancy?
answer
Order an ultrasound to look for a gestational sac or fetus. When the diagnosis is in doubt and the patient is doing poorly (e.g., hypovolemia, shock, severe abdominal pain, rebound tenderness), do a laparoscopy for definitive diagnosis and treatment, if necessary. Culdocentesis is rarely performed in a stable patient to check for blood in the pouch of Douglas (with a ruptured ectopic pregnancy) because it has a high false-negative rate.
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How is symptomatic ectopic pregnancy managed?
answer
Surgically. A tubal pregnancy, if stable and less than 3 cm in diameter, can be treated with salpingostomy and removal of the products of conception. The tube is left open to heal on its own; this strategy retains normal tubal function and fertility. If the patient's condition is unstable or the ectopic pregnancy has ruptured or is greater than 3 cm in diameter, a salpingectomy is required. In Rh-negative patients, give RhoGAM after treatment. Methotrexate (causes fetal demise) is an alternative treatment for small (<3 cm), unruptured tubal pregnancies.
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What are the problems with preexisting maternal hypertension in pregnancy?
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Preexisting hypertension (present before conception) increases the risk for IUGR and preeclampsia.
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What does a basic fetal heart monitoring strip contain?
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The fetal heart rate and the uterine contraction pattern over time.
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In fetal heart monitoring, what is the difference between early decelerations, late decelerations, and variable decelerations?
answer
In early decelerations, the peaks match up (nadir of fetal heart deceleration and peak of uterine contraction). This pattern signifies head compression (probably a vagal response) and is normal.
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In fetal heart monitoring, what is the difference between early decelerations, late decelerations, and variable decelerations?
answer
Variable decelerations are so-called because fetal heart rate deceleration varies in relation to uterine contractions. This is the most commonly encountered type of deceleration pattern and signifies cord compression. If it is seen, place the mother in the lateral decubitus position, administer oxygen by face mask, and stop any oxytocin infusion. If the fetal bradycardia is severe (<80-90 beats/min) or fails to resolve, check the fetal oxygen saturation or scalp pH.
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In fetal heart monitoring, what is the difference between early decelerations, late decelerations, and variable decelerations?
answer
Late decelerations occur when fetal heart rate deceleration comes after uterine contraction. This pattern signifies uteroplacental insufficiency and is the most worrisome. If it is seen, first place the mother in the lateral decubitus position; then give oxygen by face mask and stop oxytocin, if applicable. Next, give a tocolytic (beta2 agonist such as ritodrine or magnesium sulfate) if the mother is not in active labor and intravenous fluids if the mother is hypotensive. If the late decelerations persist, measure the fetal oxygen saturation or scalp pH. Consider preparing for operative delivery.
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What other patterns of fetal distress may be seen on a fetal heart tracing? What is a normal fetal heart rate?
answer
Loss of short-term (beat-to-beat) variability, loss of long-term variability (or normal baseline changes in heart rate over 1 minute), and prolonged fetal tachycardia (>160 beats/min). The normal fetal heart rate is 120 to 160 beats/min.
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What if the question gives you a value for fetal oxygen saturation or scalp pH?
answer
Any fetal scalp pH less than 7.2 or abnormally decreased oxygen saturation is an indication for immediate cesarean delivery. If the pH is greater than 7.2 or oxygenation is normal, you can generally continue to observe the mother and fetus.
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What should you do if shoulder dystocia or impaction occurs during vaginal delivery?
answer
The first step is to try the McRoberts maneuver. Have the mother sharply flex her thighs against her abdomen, which may free the impacted shoulder. Other maneuvers include applying suprapubic pressure, Woods screw maneuver (rotates the fetus so the anterior shoulder emerges from behind the maternal symphysis), delivery of the posterior arm, and fracture of the clavicle (risky). If these maneuvers fail, options are limited. A cesarean section is usually the procedure of choice (after pushing the infant's head back into the birth canal).
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What causes third-trimester bleeding?
answer
1) Placenta previa. 2) Abruptio placentae. 3) Uterine rupture. 4) Fetal bleeding. 5) Cervical or vaginal infections (e.g., herpes simplex virus, gonorrhea, chlamydial or candidal infection). 6) Cervical or vaginal trauma (usually from sexual intercourse). 7) Bleeding disorders (rare before delivery; more common after delivery). 8) Cervical cancer (which may occur in pregnant patients). 9) \"Bloody show\"
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True or false: The initial workup of third-trimester bleeding, like most conditions, requires a history and thorough physical examination, including a good pelvic examination.
answer
False. You should do a history and partial physical examination, but always do an ultrasound before a pelvic examination.
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Why do an ultrasound before a pelvic examination for third-trimester bleeding?
answer
When placenta previa is present, disturbing the placenta may make the bleeding worse and turn a worrisome case into an emergency.
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Define placenta previa. How does it present? How is it diagnosed and treated?
answer
True placenta previa occurs when the placenta implants in an area where it covers the cervical opening (os). Predisposing factors include multiparity, increasing maternal age, multiple gestation, and a history of prior placenta previa. Always do an ultrasound before a pelvic examination for third-trimester bleeding. The bleeding is painless and may be profuse. Ultrasound is 95% to 100% accurate in diagnosis. Mandatory cesarean section is required for delivery, but patients may be admitted to the hospital for bed and pelvic rest and tocolysis if they are preterm and stable and if the bleeding has stopped.
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Define abruptio placentae.
answer
Abruptio placentae is premature detachment of a normally situated placenta. Predisposing factors include hypertension (with or without preeclampsia), trauma, polyhydramnios with rapid decompression after membrane rupture, cocaine or tobacco use, and preterm premature rupture of membranes.
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How does abruptio placentae presents?
answer
Patients can have this condition without visible vaginal bleeding; the blood may be contained behind the placenta. Usual symptoms include pain, uterine tenderness, increased uterine tone with a hyperactive contraction pattern, and fetal distress. Abruptio placentae also may cause disseminated intravascular coagulation if fetal products enter the maternal circulation. Ultrasound detects only a small percentage of cases.
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How is abruptio placentae treated?
answer
Treat with intravenous fluids (and blood if needed) and rapid delivery (vaginal preferred).
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What factors predispose to uterine rupture?
answer
Predisposing factors include previous uterine surgery (especially prior cesarian section with vertical incision), trauma, oxytocin, grand multiparity (several previous deliveries), excessive uterine distention (e.g., multiple gestation, polyhydramnios), abnormal fetal lie, cephalopelvic disproportion, and shoulder dystocia.
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How does uterine rupture present?
answer
Uterine rupture is very painful, has a sudden and dramatic onset, and often is accompanied by maternal hypotension or shock. Other classic signs are the ability to feel fetal body parts on abdominal examination and a change in the abdominal contour. Maternal distress usually is more pronounced than fetal distress (unlike abruptio placentae, in which fetal distress is greater).
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How is uterine rupture treated?
answer
Treat with immediate laparotomy and delivery. Hysterectomy usually is required after delivery.
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What causes fetal bleeding to present as third-trimester vaginal bleeding?
answer
Visible fetal bleeding usually is caused by vasa previa or velamentous insertion of the cord, which occurs when umbilical vessels present in advance of the fetal head, usually traversing the membranes and crossing the cervical os. The biggest predisposing risk factor is multiple gestation (the greater the number of fetuses, the higher the risk). Bleeding is painless, and the mother's condition is completely stable, whereas the fetus shows worsening distress (tachycardia initially, then bradycardia as the fetus decompensates). An Apt test performed on vaginal blood is positive for fetal blood (this test differentiates fetal from maternal blood). Treat with immediate cesarean section.
question
Explain the term \"bloody show.\" How is it diagnosed?
answer
With cervical effacement, a blood-tinged mucous plug may be released from the cervical canal and heralds the onset of labor. This normal occurrence is a diagnosis of exclusion in the evaluation of third-trimester bleeding.
question
Describe the initial management of third-trimester bleeding.
answer
For all cases of third-trimester bleeding, start intravenous fluids, give blood if needed, start the patient on oxygen, and start fetal and maternal monitoring. Then order a complete blood count, coagulation profiles, ultrasound, and drug screen if drug use is suspected because cocaine causes placental abruption. Give RhoGAM if the mother is Rh-negative. A Kleihauer-Betke test can quantify fetal blood in the maternal circulation and can be used to calculate the dose of RhoGAM.
question
Define preterm labor. How is it treated?
answer
Preterm labor is defined as labor between 20 and 37 weeks of gestation. Put the mother in the lateral decubitus position, order bed and pelvic rest, and give oral or intravenous fluids and oxygen. In some cases these maneuvers stop the contractions. If they fail, you can give a tocolytic (beta2 agonist or magnesium sulfate) if no contraindications (heart disease, hypertension, diabetes, hemorrhage, ruptured membranes, cervix dilated more than 4 cm) are present. The mother can be managed as an outpatient with an oral tocolytic once she is stable
question
What are tocolytics? When is it not appropriate to give them?
answer
Tocolytics stop uterine contractions. Common examples are beta2 agonists (terbutaline, ritodrine) and magnesium sulfate. Do not give tocolytics to the mother in the presence of preeclampsia, severe hemorrhage, chorioamnionitis, IUGR, fetal demise, or fetal anomalies incompatible with survival.
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What is fetal fibronectin?
answer
Fetal fibronectin (an extracellular matrix protein that helps attach the amniotic membranes to the uterine lining) can be detected in the vaginal secretions of some women presenting with signs and symptoms of preterm labor.
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When is the test for fetal fibronectin useful?
answer
The test is most helpful when negative between 22 and 34 weeks of gestation because it indicates a very low likelihood of delivery in the next 2 weeks.
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Is the test for fibronectin more helpful when positive or negative?
answer
When fetal fibronectin is positive the woman remains at a higher risk for delivery in the next 2 weeks and a more aggressive approach to tocolysis and fetal lung maturity hastening is typically employe
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When should fetal lung maturity be evaluated?
answer
Evaluation of fetal lung maturity is indicated before elective deliveries that are, or may be, less than 39 weeks' gestation. Testing is not necessary for well-documented pregnancies that are 39 or more weeks' gestation, pregnancies that are less than 32 weeks' gestation (because fetal lung maturity is unlikely), or when delaying delivery because of fetal lung immaturity will place the mother or fetus at significant risk.
question
What tests can be used to assess fetal lung maturity?
answer
1) Lamellar body count. 2) Lecithin/sphingomyelin ratio. 3) Phosphatidylglycerol. 4)Surfactant/albumin ratio. 5) Optical density at 650 nm. 6) Foam stability index For the purposes of the USMLE, it is not necessary to know the details of these tests. No test performs better than another. All of these tests are better at predicting the absence, rather than the presence, of respiratory distress.
question
What is the role of steroids in preterm labor?
answer
Often steroids are given with tocolytics (at 24 to 34 weeks of gestation) to hasten fetal lung maturity and thus decrease the risk of respiratory distress syndrome in the neonatal period.
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Define quickening. When does it occur?
answer
Quickening is the term used to describe when the mother first detects fetal movements, usually at 18 to 20 weeks of gestation in a primigravida and 16 to 18 weeks of gestation in a multigravida.
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Give the order of fetal positions during normal labor and delivery.
answer
Descent Flexion Internal rotation Extension External rotation Expulsion
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What subtype of maternal antibody can cross the placenta?
answer
IgG is the only type of maternal antibody that crosses the placenta. This may be an important diagnostic point: an elevated neonatal IgM concentration is never normal, whereas an elevated neonatal IgG often represents maternal antibodies.
question
Explain Rh incompatibility. In what situations does it occur?
answer
Rh (or rhesus factor) blood-type incompatibility is of concern because it can lead to hemolytic disease of the newborn. Rh incompatibility occurs when the mother is Rh-negative and her infant is Rh-positive. The boards assume an understanding of inheritance of the Rh factor. If both the mother and the father are Rh-negative, there is nothing to worry about because their infant will be Rh-negative. If the father is Rh-positive, the infant has a 50/50 chance of being Rh-positive.
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How do you detect and manage potential hemolytic disease of the newborn?
answer
If indicated by maternal and potential fetal blood type, check maternal titers of Rh antibody every month, starting in the seventh month of gestation. Give RhoGAM automatically at 28 weeks and within 72 hours after delivery as well as after any procedures that may cause transplacental hemorrhage
question
True or false: The first child is usually the most severely affected by Rh incompatibility
answer
False. Previous maternal sensitization is required for disease to occur. In other words, if a nulliparous Rh-negative mother has never received blood products, her first Rh-positive infant will not be affected by hemolytic disease—except in the rare case of sensitization during the first pregnancy from undetected fetomaternal bleeding, which commonly occurs later in the pregnancy and in most instances can be prevented by RhoGAM administration at 28 weeks. The second Rh-positive infant, however, will be affected—unless you, the astute board taker, administer RhoGAM at 28 weeks and within 72 hours after delivery during the first pregnancy. Any history of blood transfusion, abortion, ectopic pregnancy, stillbirth, or delivery can cause sensitization.
question
How much RhoGAM should you give if the maternal Rh antibody titer is extremely high?
answer
In this setting RhoGAM is worthless because sensitization has already occurred. RhoGAM administration is a good example of primary prevention. Close fetal monitoring for hemolytic disease is required.
question
How do you recognize, monitor, and treat hemolytic disease of the newborn?
answer
Hemolytic disease of the newborn in its most severe form causes fetal hydrops (edema, ascites, pleural and/or pericardial effusions) and death. Amniotic fluid spectrophotometry and ultrasound can help gauge the severity of fetal hemolysis. Treatment of hemolytic disease involves (1) delivery, if the fetus is mature (check lung maturity with a lecithin-to-sphingomyelin ratio); (2) intrauterine transfusion; and (3) phenobarbital, which helps the fetal liver break down bilirubin by inducing enzymes.
question
True or false: ABO blood group incompatibility can cause hemolytic disease of the newborn
answer
True. ABO blood group incompatibility can cause hemolytic disease of the newborn when the mother is type O and the infant is type A, B, or AB. This condition does not require previous sensitization because IgG antibodies (which can cross the placenta) occur naturally in mothers with blood type O—but not in mothers with other blood types. The hemolytic disease is usually less severe than with Rh incompatibility, but treatment is the same. In rare instances, other minor blood antigens also may cause a reaction.
question
When should RhoGAM be given?
answer
To reiterate, give RhoGAM only when the mother is Rh-negative and the father is Rh-positive or his blood type is unknown. During routine prenatal care, check for Rh antibodies at the first visit. If the test is positive, do not give RhoGAM—you are too late. Otherwise, give RhoGAM routinely at 28 weeks and immediately after delivery. Also give RhoGAM after an abortion, stillbirth, ectopic pregnancy, amniocentesis, CVS, and any other invasive procedure that may cause transplacental bleeding during pregnancy.
question
Define premature rupture of membranes (PROM). How is it diagnosed?
answer
PROM is rupture of the amniotic sac before the onset of labor. Diagnosis of rupture of membranes (whether premature or not) is based on history, sterile speculum examination, and/or a positive nitrazine test. The sterile speculum examination shows pooling of amniotic fluid and a ferning pattern when the fluid is placed on a microscopic slide and allowed to dry. Nitrazine paper turns blue in the presence of amniotic fluid. Ultrasound should be done in cases of PROM to assess amniotic fluid volume as well as gestational age and any anomalies that may be present
question
What usually follows membrane rupture? What should you do if it does not occur?
answer
Spontaneous labor usually follows membrane rupture; for this reason, an amniotomy may be done in an attempt to induce labor if membranes do not rupture spontaneously. If labor does not occur within 6 to 8 hours of membrane rupture, the mother is term, and if the cervix is favorable, labor should be induced. Labor is induced because the main risk of PROM is infection, which may occur in the mother (chorioamnionitis) and/or the infant (neonatal sepsis, pneumonia, meningitis). The usual culprits are group B streptococci, Escherichia coli, or Listeria sp.
question
Define preterm premature rupture of membranes (PPROM). How is it managed?
answer
PPROM is defined as premature rupture of membranes before 36 to 37 weeks of gestation. The risk of infection increases with the duration of ruptured membranes. Do a culture and Gram stain of the amniotic fluid. If it is negative, treatment simply involves pelvic and bed rest with frequent follow-up. If the culture is positive for group B streptococci, treat the mother with penicillin G or ampicillin, even if she is asymptomatic.
question
How does chorioamnionitis present and how is it treated?
answer
Patients with chorioamnionitis have presenting symptoms of fever and a tender, irritable uterus, usually after delivery. Antepartum chorioamnionitis may occur in patients with PROM. Do a culture and Gram stain of the cervix and amniotic fluid, and treat with antibiotics such as ampicillin plus gentamicin while awaiting culture results.
