Obstetrics Flashcards
A patient who is taking birth control pills presents with amenorrhea. What is the likely cause?
Pregnancy. No form of contraception is 100% effective (including tubal ligation), especially when patient compliance is required.
List the symptoms and signs of pregnancy.
q2
Which vitamin should all pregnant women take? Why?
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.
Define macrosomia. What is the likely cause?
Macrosomia is defined as a newborn that weighs more than 4 kg (roughly 9 lb). The cause is maternal diabetes mellitus until proven otherwise.
What routine tests should be obtained for all pregnant patients?
q5
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?
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).
When is ultrasound most accurate at estimating the fetal age?
At 16 to 20 weeks, the biparietal diameter (measured on ultrasound) gives the most accurate estimate of fetal age.
What is a hydatiform mole? What are the clues to its presence?
A hydatiform mole is one form of gestational trophoblastic neoplasia, in which the products of con- ception basically become a tumor. Look for the following clues: ■ Preeclampsia before the third trimester. ■ An hCG level that does not return to zero after delivery (or abortion/miscarriage) or one that rises rapidly during pregnancy. ■ 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. ■ Uterine size/date discrepancy. ■ “Snowstorm” pattern on ultrasound.
Distinguish between complete and partial moles. How are hydatiform moles treated?
Complete moles have a karyotype of 46 XX (with all chromosomes from the father) and no fetal tis- sue. Incomplete moles usually have a karyotype of 69 XXY with fetal tissue in the tumor. 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).
How is intrauterine growth retardation (IUGR) defined? What causes it?
IUGR is defined as fetal size below the tenth percentile for age. 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). For a discussion of TORCH infections, see question 36.
When should ultrasound be used to evaluate the fetus?
The indications for ultrasound are now quite liberal. 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).
How is fetal well-being evaluated?
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. 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. 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.
True or false: A biophysical profile often is used in high-risk pregnancies in the absence of obvious problems.
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.
True or false: Aspirin should be avoided during pregnancy.
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).
Define postterm pregnancy. Why is it a major concern? How is it treated?
Postterm pregnancy is defined as more than 42 weeks of gestation. Both prematurity and postmatu- rity increase perinatal morbidity and mortality rates. With postmaturity, dystocia (or difficult delivery) becomes more common because of the increased size of the infant. 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. A 2012 meta-analysis demonstrated that routine labor induction at greater than 41 weeks compared with expectant management resulted in lower perinatal mortality and a lower rate of meconium aspiration syndrome.
What two rare disorders are associated with prolonged gestation?
Anencephaly and placental sulfatase deficiency.
What are the normal changes and complaints in pregnancy?
Normal changes in pregnancy include nausea or vomiting (morning sickness), amenorrhea, heavy (pos- sibly 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.
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 alpha- fetoprotein (AFP) level in maternal serum.
Maternal AFP is most accurate when measured between 15 and 20 weeks of gestation. 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, gastroschi- sis), multiple gestation, or inaccurate dates.
What should be done if the AFP is elevated?
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.
What further testing should a patient undergo if the AFP remains elevated?
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.
What prenatal tests are available to screen for Down syndrome?
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.
What is the first trimester combined test? When is it performed?
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.
Describe the integrated tests.
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 evalua- tion 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.
Describe sequential testing.
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.
Describe contingent testing.
Contingent testing has not yet been proven efficacious in a prospective clinical trial and probably will not be tested on the USMLE; however, contingent screening is defined in terms of three risk cut-offs: (1) women at very high risk of having a fetus with Down syndrome after first trimester testing are offered immediate invasive prenatal diagnosis, (2) women at very low risk are provided with their risk estimate and require no additional testing, and (3) women at intermediate risk receive second trimester marker testing.
What is the quadruple test? For whom is it typically used? When is it performed?
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.
What is a maternal plasma-based test?
This is the newest option that is just becoming widely available and may someday make many of these other tests obsolete. This test, 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 associ- ated 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).
What is the next step if a woman has a positive screening test for Down syndrome?
Offer fetal karyotype determination. This is done by CVS in the first trimester and by amniocentesis in the second trimester.
Why is CVS done instead of amniocentesis in some cases?
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.
True or false: CVS can detect neural tube defects but not genetic disorders.
False. CVS can detect genetic or chromosomal disorders but not neural tube defects.
Specify the effects of Thalidomide on an exposed fetus.
Phocomelia (absence of long bones and flipperlike appearance of hands)
Specify the effects of Antineoplastics on an exposed fetus.
many
Specify the effects of Tetracycline on an exposed fetus.
Yellow or brown teeth
Specify the effects of Aminoglycosides on an exposed fetus.
Deafness
Specify the effects of Valproic acid on an exposed fetus.
Spina bifida, hypospadias
Specify the effects of Progesterone on an exposed fetus.
Masculinization of female fetus
Specify the effects of Cigarettes on an exposed fetus.
Intrauterine growth retardation, low birth weight, prematurity
Specify the effects of OCP on an exposed fetus.
VACTERL syndrome: Vertebral anomalies, imperforate Anus, Cardiac anomalies, TracheoEsophageal fistula, Renal anomalies, Limb anomalies
Specify the effects of Lithium on an exposed fetus.
Cardiac (Ebstein) anomalies
Specify the effects of Radiation on an exposed fetus.
Intrauterine growth retardation, CNS defects, eye defects, malignancy (e.g., leukemia)
Specify the effects of Alcohol on an exposed fetus.
Fetal alcohol syndrome
Specify the effects of Phenytoin on an exposed fetus.
Craniofacial, limb, and cerebrovascular defects; mental retardation
Specify the effects of Warfarin on an exposed fetus.
Craniofacial defects, intrauterine growth retardation, CNS malformation, stillbirth
Specify the effects of Carbamazepine on an exposed fetus.
Fingernail hypoplasia, craniofacial defects
Specify the effects of Isotretinoin on an exposed fetus.
CNS, craniofacial, ear, and cardiovascular defects
Specify the effects of Iodine on an exposed fetus.
Goiter, neonatal hypothyroidism
Specify the effects of Cocaine on an exposed fetus.
Cerebral infarcts, mental retardation
Specify the effects of Diazepam on an exposed fetus.
Cleft lip and/or palate
Specify the effects of Diethylstilbestrol on an exposed fetus.
Clear cell vaginal cancer, adenosis, cervical incompetence
List the teratogenic effects of maternal diabetes mellitus. What is the best way to reduce these complications?
q32
What other problems does maternal diabetes cause in pregnancy?
In the mother, diabetes can result in polyhydramnios and preeclampsia (as well as the complica- tions 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.
True or false: Oral hypoglycemic agents should not be used during pregnancy.
True. Use insulin to treat diabetes if diet and exercise cannot control glucose levels. Oral hypoglyce- mics, unlike insulin, may cross the placenta and cause fetal hypoglycemia.
What commonly used drugs are generally considered safe in pregnancy?
A short list of drugs that are generally safe in pregnancy includes acetaminophen, penicillins, cepha- losporins, erythromycin, nitrofurantoin, histamine-2 receptor blockers, antacids, heparin, hydralazine, methyldopa, labetalol, insulin, and docusate.
What are the TORCH syndromes? What do they cause?
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. T = Toxoplasma gondii: Look for exposure to cats. Specific defects include intracranial calcifica- tions and chorioretinitis. O = Other: Varicella-zoster causes limb hypoplasia and scarring of the skin. Syphilis causes rhini- tis, saber shins, Hutchinson teeth, interstitial keratitis, and skin lesions. R = Rubella: 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. C = Cytomegalovirus: Most common infection of the TORCH group. Look for deafness, cerebral calcifications, and microphthalmia. H = Herpes: Look for vesicular skin lesions (with positive Tzanck smears) and history of maternal herpes lesions.
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.
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.
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?
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.
What should you do if a pregnant woman has genital herpes?
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.
What should you do for the child if the mother has chronic hepatitis B or chickenpox?
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.
How do you treat gonorrheal and chlamydial genital infections during pregnancy?
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.
How is tuberculosis treated in pregnancy?
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.
What are the signs of placental separation during delivery?
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.
