USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 311:

  A woman with type 1 diabetes is at increased risk for having a fetus with which of the following congenital anomalies?

  A. gastroschisis

  B. duodenal atresia

  C. cleft lip and palate

  D. congenital heart defects

  E. diaphragmatic hernia

  Correct Answer: D Section: (none)

  Explanation:

  In general, women with diabetes mellitus are at increased risk for congenital abnormalities as well as spontaneous abortion, with the risk rising in direct relationship to the maternal hemoglobin A1C. The risk is particularly increased when the periconception hemoglobin A1C value exceeds 10%. In addition to congenital heart defects, which are increased approximately fivefold over the general population (2.5% vs. 0.5%), open neural defects are thought to be 10 times more common

• Question 312:

  Which of the following agents is considered the first-line therapy for prevention of eclamptic seizures?

  A. diazepam

  B. phenytoin

  C. magnesium sulfate

  D. phenobarbital

  E. carbamazepine

  Correct Answer: C Section: (none)

  Explanation:

  Magnesium sulfate has been demonstrated in randomized-controlled trials to be superior to any other anticonvulsant agent in prevention of initial eclamptic seizures and prevention of recurrence of eclampsia. Phenytoin would be considered the best alternative in patients who had an absolute contraindication to magnesium sulfate therapy (such as women with myasthenia gravis).

• Question 313:

  A35-year-old woman with two prior term pregnancies presents for her first prenatal visit at 12 weeks' gestation. She recalls having had hypertension near the end of her first pregnancy. She believes her blood pressure has been normal since, but admits that she rarely seeks preventive health care visits, and that her last examination by a physician was more than 2 years ago. Today, you find her blood pressure to be 160/100.

  Her blood pressure comes under good control after initiating medication and remains well controlled until the 36th week, when her blood pressure is noted to have risen again to 170/110. She is also noted to have 3+ proteinuria on urine dipstick testing.

  For which of the following complications is she at risk?

  A. eclampsia

  B. fetal macrosomia

  C. abnormal progress of labor

  D. postpartum hemorrhage

  E. breech presentation

  Correct Answer: A Section: (none)

  Explanation:

  The angiotensin-converting enzyme inhibitors (and angiotensin receptor blockers) are contraindicated in pregnancy due to their potential to cause decreased fetal renal perfusion, ultimately resulting in fetal oliguria, oligohydramnios, renal tubular dysplasia, and neonatal anuric renal failure, as well as defects in ossification of the fetal skull. These adverse effects occur during the second and third trimesters of pregnancy. If a woman conceives while taking an angiotensin-converting enzyme inhibitor, she should be changed to another agent during the first trimester.

  Preeclampsia causes 5070% of cases of hypertension in pregnancy. Mild preeclampsia is characterized by an increase in systolic BP of 30 mmHg, an increase in diastolic BP of 15 mmHg, or an absolute reading of 140/90 mmHg in a pregnant patient with minimal proteinuria and pathologic edema. A systolic BP greater than 160/110 mmHg with significant proteinuria (>5000 mg/24 h) and evidence of end-organ damage indicate severe preeclampsia. End organ damage results from increased vascular reactivity, third spacing of fluids, and platelet activation. Complications include oliguria, the syndrome of hemolysis, elevated liver function tests, and low platelets (HELLP) and eclamptic seizures. Seizure prophylaxis is effective in both primary prevention of eclampsia and in prevention of recurrent seizures. Fetal macrosomia occurs more commonly in pregnancies complicated by diabetes. Abnormal labor progress and postpartum hemorrhage as well as breech presentation are not more common in pregnancies complicated by preeclampsia.

• Question 314:

  A35-year-old woman with two prior term pregnancies presents for her first prenatal visit at 12 weeks' gestation. She recalls having had hypertension near the end of her first pregnancy. She believes her blood pressure has been normal since, but admits that she rarely seeks preventive health care visits, and that her last examination by a physician was more than 2 years ago. Today, you find her blood pressure to be 160/100.

  Which of the following antihypertensive agents would be contraindicated for management of her hypertension during pregnancy?

  A. labetalol

  B. alpha-methyldopa

  C. enalapril

  D. nifedipine

  E. hydralazine

  Correct Answer: C Section: (none)

  Explanation:

  The angiotensin-converting enzyme inhibitors (and angiotensin receptor blockers) are contraindicated in pregnancy due to their potential to cause decreased fetal renal perfusion, ultimately resulting in fetal oliguria, oligohydramnios, renal tubular dysplasia, and neonatal anuric renal failure, as well as defects in ossification of the fetal skull. These adverse effects occur during the second and third trimesters of pregnancy. If a woman conceives while taking an angiotensin-converting enzyme inhibitor, she should be changed to another agent during the first trimester.

  Preeclampsia causes 5070% of cases of hypertension in pregnancy. Mild preeclampsia is characterized by an increase in systolic BP of 30 mmHg, an increase in diastolic BP of 15 mmHg, or an absolute reading of 140/90 mmHg in a pregnant patient with minimal proteinuria and pathologic edema. A systolic BP greater than 160/110 mmHg with significant proteinuria (>5000 mg/24 h) and evidence of end-organ damage indicate severe preeclampsia. End organ damage results from increased vascular reactivity, third spacing of fluids, and platelet activation. Complications include oliguria, the syndrome of hemolysis, elevated liver function tests, and low platelets (HELLP) and eclamptic seizures. Seizure prophylaxis is effective in both primary prevention of eclampsia and in prevention of recurrent seizures. Fetal macrosomia occurs more commonly in pregnancies complicated by diabetes. Abnormal labor progress and postpartum hemorrhage as well as breech presentation are not more common in pregnancies complicated by preeclampsia.

• Question 315:

  A 25-year-old nulligravid woman presents as a new patient to your gynecology practice. She has recently moved to the area. She is a healthy woman with no medical problems and is currently using oral contraceptives without problems. She informs you that she and her husband are planning to start a family within the next year. On review, you find her family history is unremarkable, but she informs you that her husband's sister has cystic fibrosis.

  If she and her husband were both known to carry a cystic fibrosis gene mutation, what would be their likelihood of having a child with cystic fibrosis?

  A. 100%

  B. 75%

  C. 50%

  D. 33%

  E. 25%

  Correct Answer: E Section: (none)

  Explanation:

  Cystic fibrosis is the most common hereditary condition in Whites with a carrier frequency of 1 in 25. The American College of Obstetricians and Gynecologists, the American College of Medical Genetics, and the National Institutes of Health have recommended that cystic fibrosis carrier screening be offered to all White couples either pregnant or considering a pregnancy, and that the availability of screening be discussed with members of other ethnic groups who have a lower frequency of cystic fibrosis carrier state. Cystic fibrosis is inherited in an autosomal recessive fashion, so for a couple in which both mother and father are carriers the risk of having an affected child is 25% or 1 in 4. In the case presented, in which the husband's sister has cystic fibrosis, his likelihood of being a carrier is 2 in 3 (since he has an affected sibling, both of his parents are obligate carriers, and since he is not affected, he is either a noncarrier [1 in 3] or a carrier [2 in 3]). This pattern is true for all autosomal recessive disorders.

• Question 316:

  A 25-year-old nulligravid woman presents as a new patient to your gynecology practice. She has recently moved to the area. She is a healthy woman with no medical problems and is currently using oral contraceptives without problems. She informs you that she and her husband are planning to start a family within the next year. On review, you find her family history is unremarkable, but she informs you that her husband's sister has cystic fibrosis.

  Given that the husband's sister has cystic fibrosis, what is the likelihood that he is a carrier?

  A. 100% chance of being a carrier

  B. 67% (2 in 3) chance of being a carrier

  C. 50% (1 in 2) chance of being a carrier

  D. 25% (1 in 4) chance of being a carrier

  E. his chance of being a carrier is no greater than the general population

  Correct Answer: B Section: (none)

  Explanation:

  Cystic fibrosis is the most common hereditary condition in Whites with a carrier frequency of 1 in 25. The American College of Obstetricians and Gynecologists, the American College of Medical Genetics, and the National Institutes of Health have recommended that cystic fibrosis carrier screening be offered to all White couples either pregnant or considering a pregnancy, and that the availability of screening be discussed with members of other ethnic groups who have a lower frequency of cystic fibrosis carrier state. Cystic fibrosis is inherited in an autosomal recessive fashion, so for a couple in which both mother and father are carriers the risk of having an affected child is 25% or 1 in 4. In the case presented, in which the husband's sister has cystic fibrosis, his likelihood of being a carrier is 2 in 3 (since he has an affected sibling, both of his parents are obligate carriers, and since he is not affected, he is either a noncarrier [1 in 3] or a carrier [2 in 3]). This pattern is true for all autosomal recessive disorders.

• Question 317:

  A 25-year-old nulligravid woman presents as a new patient to your gynecology practice. She has recently moved to the area. She is a healthy woman with no medical problems and is currently using oral contraceptives without problems. She informs you that she and her husband are planning to start a family within the next year. On review, you find her family history is unremarkable, but she informs you that her husband's sister has cystic fibrosis.

  What is the approximate prevalence of cystic fibrosis carrier state in White individuals?

  A. 1in10

  B. 1in25

  C. 1in50

  D. 1in100

  E. 1in200

  Correct Answer: B Section: (none)

  Explanation:

  Cystic fibrosis is the most common hereditary condition in Whites with a carrier frequency of 1 in 25. The American College of Obstetricians and Gynecologists, the American College of Medical Genetics, and the National Institutes of Health have recommended that cystic fibrosis carrier screening be offered to all White couples either pregnant or considering a pregnancy, and that the availability of screening be discussed with members of other ethnic groups who have a lower frequency of cystic fibrosis carrier state. Cystic fibrosis is inherited in an autosomal recessive fashion, so for a couple in which both mother and father are carriers the risk of having an affected child is 25% or 1 in 4. In the case presented, in which the husband's sister has cystic fibrosis, his likelihood of being a carrier is 2 in 3 (since he has an affected sibling, both of his parents are obligate carriers, and since he is not affected, he is either a noncarrier [1 in 3] or a carrier [2 in 3]). This pattern is true for all autosomal recessive disorders.

• Question 318:

  A 28-year-old White G1 woman presents to your office for an initial obstetric visit. Her LMP is certain and allows you to estimate a 9-week gestational age today. She denies bleeding, cramping, or other symptoms of concern. She is excited about being pregnant. She has already started taking her prenatal vitamins with folic acid. She reports no significant past medical history. In fact, she states that she has not been to a doctor in many years because she has not had any problems. She has had no surgeries. She does not smoke. She drank alcohol socially prior to pregnancy but has not consumed any alcohol since she became pregnant. She has family history of hypertension, but no other significant history is elicited. On physical examination, her blood pressure is 110/60. She is healthy appearing, and there are no significant findings on examination. Your pelvic examination confirms uterine size consistent with stated dates. As part of a routine laboratory evaluation, you decide to check a thyroid-stimulating hormone (TSH). The TSH is 0.4 IU/ mL (normal range 0.55.5) and a free T4 of 1.8 ng/dL (normal range 0.72.0).

  What is the most appropriate management of this condition?

  A. thyroid ablation with radioactive iodine

  B. prescription for propylthiouracil (PTU)

  C. prescription for propranolol

  D. subtotal thyroidectomy

  E. no intervention is necessary as the problem will go away after the pregnancy

  Correct Answer: B Section: (none)

  Explanation:

  In question 66, this patient likely does not have thyroid disease. She is asymptomatic, has a normal physical examination, and her free T4 is normal. hCG shares a chemical subunit with TSH. The circulating hCG can cause suppression of the thyroid. This is a transient change and does not represent true thyroid disease. Graves' disease is the most common cause of hyperthyroidism in pregnancy. It is the cause of 9095% of such cases. Patients may complain of rapid heartbeat, weight loss, and GI symptoms such as nausea and vomiting. On examination, you may palpate diffuse thyromegaly and may note exophthalmos. The other listed causes of thyrotoxicosis are much less common in pregnancy, accounting for the remaining 510% of cases. Treatment of this problem is necessary because thyrotoxic women are at increased risk of perinatal mortality, preterm delivery, and maternal heart failure.

  Treatment is typically with PTU or methimazole. Propranolol can be used initially to reduce symptoms but does not address the underlying problem. Surgery should be reserved for women who do not respond to medical therapy. Radioactive iodine is contraindicated during pregnancy as it can ablate fetal thyroid tissue, leading to the possibility of congenital hypothyroidism.

• Question 319:

  A 28-year-old White G1 woman presents to your office for an initial obstetric visit. Her LMP is certain and allows you to estimate a 9-week gestational age today. She denies bleeding, cramping, or other symptoms of concern. She is excited about being pregnant. She has already started taking her prenatal vitamins with folic acid. She reports no significant past medical history. In fact, she states that she has not been to a doctor in many years because she has not had any problems. She has had no surgeries. She does not smoke. She drank alcohol socially prior to pregnancy but has not consumed any alcohol since she became pregnant. She has family history of hypertension, but no other significant history is elicited. On physical examination, her blood pressure is 110/60. She is healthy appearing, and there are no significant findings on examination. Your pelvic examination confirms uterine size consistent with stated dates. As part of a routine laboratory evaluation, you decide to check a thyroid-stimulating hormone (TSH). The TSH is 0.4 IU/ mL (normal range 0.55.5) and a free T4 of 1.8 ng/dL (normal range 0.72.0).

  What is the most likely cause of this patient's hyperthyroidism?

  A. toxic adenoma

  B. multinodular goiter

  C. hyperemesis gravidarum

  D. lymphocytic thyroiditis

  E. Grave's disease

  Correct Answer: E Section: (none)

  Explanation:

  In question 66, this patient likely does not have thyroid disease. She is asymptomatic, has a normal physical examination, and her free T4 is normal. hCG shares a chemical subunit with TSH. The circulating hCG can cause suppression of the thyroid. This is a transient change and does not represent true thyroid disease. Graves' disease is the most common cause of hyperthyroidism in pregnancy. It is the cause of 9095% of such cases. Patients may complain of rapid heartbeat, weight loss, and GI symptoms such as nausea and vomiting. On examination, you may palpate diffuse thyromegaly and may note exophthalmos. The other listed causes of thyrotoxicosis are much less common in pregnancy, accounting for the remaining 510% of cases. Treatment of this problem is necessary because thyrotoxic women are at increased risk of perinatal mortality, preterm delivery, and maternal heart failure.

  Treatment is typically with PTU or methimazole. Propranolol can be used initially to reduce symptoms but does not address the underlying problem. Surgery should be reserved for women who do not respond to medical therapy. Radioactive iodine is contraindicated during pregnancy as it can ablate fetal thyroid tissue, leading to the possibility of congenital hypothyroidism.

• Question 320:

  A 28-year-old White G1 woman presents to your office for an initial obstetric visit. Her LMP is certain and allows you to estimate a 9-week gestational age today. She denies bleeding, cramping, or other symptoms of concern. She is excited about being pregnant. She has already started taking her prenatal vitamins with folic acid. She reports no significant past medical history. In fact, she states that she has not been to a doctor in many years because she has not had any problems. She has had no surgeries. She does not smoke. She drank alcohol socially prior to pregnancy but has not consumed any alcohol since she became pregnant. She has family history of hypertension, but no other significant history is elicited. On physical examination, her blood pressure is 110/60. She is healthy appearing, and there are no significant findings on examination. Your pelvic examination confirms uterine size consistent with stated dates. As part of a routine laboratory evaluation, you decide to check a thyroid-stimulating hormone (TSH). The TSH is 0.4 IU/ mL (normal range 0.55.5) and a free T4 of 1.8 ng/dL (normal range 0.72.0).

  You counsel the patient that she most likely has which of the following?

  A. hypothyroidism

  B. hyperthyroidism

  C. normal thyroid function, with laboratory values altered by hormone interactions associated with pregnancy

  D. a drug reaction altering thyroid function

  E. a thyroid nodule The patient returns to the clinic for routine prenatal visits. At approximately 28 weeks' gestational age, you decide to recheck her thyroid levels. At this visit, her TSH is 0.1 IU/mL, her total T4 is 15 ng/dL (normal range 4.512.5), and her free T4 is 2.4 ng/dL.

  Correct Answer: C Section: (none)

  Explanation:

  In question 66, this patient likely does not have thyroid disease. She is asymptomatic, has a normal physical examination, and her free T4 is normal. hCG shares a chemical subunit with TSH. The circulating hCG can cause suppression of the thyroid. This is a transient change and does not represent true thyroid disease. Graves' disease is the most common cause of hyperthyroidism in pregnancy. It is the cause of 9095% of such cases. Patients may complain of rapid heartbeat, weight loss, and GI symptoms such as nausea and vomiting. On examination, you may palpate diffuse thyromegaly and may note exophthalmos. The other listed causes of thyrotoxicosis are much less common in pregnancy, accounting for the remaining 510% of cases. Treatment of this problem is necessary because thyrotoxic women are at increased risk of perinatal mortality, preterm delivery, and maternal heart failure.

  Treatment is typically with PTU or methimazole. Propranolol can be used initially to reduce symptoms but does not address the underlying problem. Surgery should be reserved for women who do not respond to medical therapy. Radioactive iodine is contraindicated during pregnancy as it can ablate fetal thyroid tissue, leading to the possibility of congenital hypothyroidism.