USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 601:

  A healthy 29-year-old gravida 2 woman at 39 weeks has been in labor for 3 hours. She had a positive vaginal-anal culture for GBS at 37 weeks' gestation. Which one of the following statements is correct?

  A. Asymptomatic rectovaginal colonization is present in 60% of pregnant women.

  B. The transmission rate from mother to baby is approximately 25%.

  C. A rectovaginal culture should have been obtained at the first prenatal visit.

  D. Neonatal sepsis occurs in 1% of colonized mothers.

  E. Treatment with penicillin in labor is necessary only for heavy colonized mothers.

  Correct Answer: D

  Approximately 20% of pregnant women have positive rectovaginal cultures. Vertical transmission rate from mother to baby is approximately 75%. A rectovaginal culture is not indicated at the first prenatal visit because the pregnant woman may subsequently convert from a negative to a positive culture. For this reason, all pregnant women should have a rectovaginal culture at 3637 gestational weeks. If the woman goes into preterm labor before a culture is obtained, she should be treated with penicillin (gentamicin if she is penicillin allergic). The rate of neonatal sepsis is 1% of colonized mothers, a serious infection that may cause pneumonia, meningitis, and death.

• Question 602:

  Your patient has just had twins and wonders if there is any way to determine whether the twins are identical. You correctly tell her which of the following?

  A. Close examination of the placenta can often provide this answer.

  B. There is no way to tell unless one is a girl and one a boy.

  C. Only matching of human lymphocyte antigens could determine this with certainty.

  D. Identical twins occur only once in about 80 births of twins.

  E. It is unlikely because the birth weights differed by more than 200 g.

  Correct Answer: C

  Different-sex twins must be dizygous. Prenatal ultrasound can detect monochorionic, monoamnionic twins, and these must be monozygous. For same-sex twins, careful examination of the amniotic membranes after birth can reveal monozygous twins if the placental membranes are monochorionic. Dichorionic membranes can occur with either monozygous or dizygous twins. Ultimately, assessment of DNA polymorphism is the best way to determine twin zygosity

• Question 603:

  On the first pelvic examination of an 18-yearold nulligravida, a soft, fluctuant mass is found in the superior aspect of the right labia majora. This is asymptomatic. She tells you it has been present for several years and seems to be enlarging slightly. There is no defect in the inguinal ring. Which of the following is the most likely diagnosis?

  A. vulvar varicosities

  B. inguinal hernia

  C. femoral hernia

  D. cyst of the canal of Nuck

  E. granuloma inguinale

  Correct Answer: D

  The most likely diagnosis is a cyst of the canal of Nuck. These arise from inclusions of the peritoneum at the inferior insertion of the round ligament into the labia majora. They are analogous to a spermatic cord hydrocele and are typically found at the superior aspect of the labia majora. Vulvar varicosities usually involve most of the labia, occur in older and parous women, and have a classical "bag of worms" appearance. Given the physical findings, a hernia is unlikely. An ultrasound may be useful to distinguish a hernial sac from a cyst of the canal of Nuck. One-third of women with a cyst of the canal of Nuck may have a coexistent inguinal hernia.

• Question 604:

  A 22-year-old woman with cystic fibrosis is engaged to be married and asks you about childbearing. How should you advise her?

  A. An amniocentesis should be done to detect fetal cystic fibrosis.

  B. Pregnancy is contraindicated because maternal mortality is significantly increased.

  C. Her children have a 25% chance of having cystic fibrosis.

  D. Pregnancy and delivery are usually successful with special care and precautions.

  E. She should use nasal oxygen throughout pregnancy to minimize fetal hypoxemia.

  Correct Answer: D

  With improved care, women with cystic fibrosis now survive into the reproductive age and are capable of carrying a pregnancy successfully. No special precautions such as prolonged hospitalization, oxygen supplementation, bed rest, or others are necessary. Likewise, there is no need for routine cesarean section or other labor modifications, except ensuring adequate hydration and normal serum electrolytes. An amniocentesis is unnecessary. There is no constituent of amniotic fluid that is diagnostic of cystic fibrosis. Also, the fetus is at risk for cystic fibrosis only if the father is a carrier. If not, the fetus will be a carrier only. Chorionic villus biopsy can be done to determine whether the fetus has cystic fibrosis if the father carries one of the 150+ alleles for cystic fibrosis or the couple had a previously affected child. It is becoming the standard of care to screen routinely pregnant women for the cystic fibrosis gene. Currently, routine screening will identify approximately 80% of carriers of the cystic fibrosis gene.

• Question 605:

  A13-year-old girl had growth of breast buds at 11 years, followed by the appearance of pubic hair between the ages of 11 1/2 and 12 years. Which pubertal event is most likely to occur next?

  A. beginning of accelerated growth

  B. menarche

  C. Tanner stage 5 breast development

  D. maximal growth rate

  E. Tanner stage 5 pubic hair

  Correct Answer: D

  The mean age of onset of any pubertal event is approximately 11 years, beginning with the appearance of breast buds. Pubic hair appears approximately 6 months later, and this is followed by the peak height velocity (greatest rate of linear growth per unit time). Six to 12 months later, menstrual bleeding begins. Increased rate of growth begins early in the pubertal process. The sequence of pubertal events and the approximate age of appearance of each event is sufficiently predictable that significant variation in age of onset or sequence should lead to an evaluation of a cause of abnormal puberty.

• Question 606:

  An 18-year-old nullipara has suddenly stopped menstruating. She recently lost 8.6 kg when she started long-distance running. The laboratory test most consistent with her cause of secondary amenorrhea is which of the following?

  A. a serum prolactin level of 86 ng/mL normal <20)

  B. a serum LH level of 48 mIU/mL (normal 635)

  C. a serum estradiol level of 128 pg/mL (normal 40300)

  D. a serum FSH level of 3 mIU/mL (normal 518)

  E. a serum testosterone level of 156 ng/dL (normal 40110)

  Correct Answer: D

  Women with amenorrhea owing to weight loss and stress have decreased hypothalamic secretion of GnRH, and secondarily decreased serum levels of FSH and LH. As a consequence, serum estradiol levels will be low. While women with weight loss amenorrhea may have mild hirsutism, it is probably the result of a decreased estrogen secretion and decreased estrogen: androgen ratio, rather than an increase in serum testosterone levels.

• Question 607:

  A 58-year-old woman with stage II epithelial ovarian cancer undergoes successful surgical debulking followed by chemotherapy with carboplatin and radiation therapy. Subsequently, she develops nonpitting edema of both legs and pain and numbness in her legs. Which of the following is the most likely cause of her pain and numbness?

  A. nerve damage caused by the pelvic lymphadenectomy

  B. lymphedema

  C. carboplatin therapy

  D. radiation therapy

  E. recurrent ovarian cancer

  Correct Answer: C

  The nonpitting edema of her legs is likely the result of lymphedema. This may cause discomfort or pain in her legs, but not hypesthesia. The most likely cause of the peripheral neuropathy is the carboplatin. Toxicity at doses higher than 100 mg/m2 limit its use and also limit the ability to study various doses alone and in combination with other chemotherapeutic agents, such as paclitaxel (Taxol), which may also cause peripheral neuropathy. Nonetheless, the combination of tumor debulking, pelvic and paraaortic lymph node dissection, combination paclitaxel and carboplatin, and radiation offers the longest disease-free interval.

• Question 608:

  At a follow-up routine prenatal visit, the uterine fundus of a healthy 23-year-old pregnant woman is palpated halfway between her symphysis pubis and umbilicus. Which of the following is the most appropriate test to order at this stage of her pregnancy?

  A. serum human immunodeficiency virus (HIV) titer

  B. glucose tolerance test

  C. amniocentesis

  D. maternal serum alpha-fetoprotein (MSAFP)

  E. cervical culture for group B Streptococcus (GBS)

  Correct Answer: D

  The fundal height corresponds to 16 gestational weeks. Between 15 and 20 weeks, screening for open neural tube defects should be offered. In addition to MSAFP, the American College of Obstetricians and Gynecologists recommends hCG and unconjugated estriol to screen for Down syndrome and trisomy 18 as well. This triad of tests is called a triple screen or triple marker screen. Reported sensitivity of the triple screen is between 57 and 67% and the false positive rate is 5%. An abnormal result must be evaluated further by ultrasonography to identify the presence or absence of open neural tube defects or abdominal wall defects (increased MSAFP) or trisomy disorder (decreased MSAFP and unconjugated estriol, increased hCG). In skilled hands, an ultrasound reduces the risk of such an anomaly by 95%. If the diagnosis is still uncertain, the woman should be offered amniocentesis for measurement of alphafetoprotein (AFP) and acetylcholinesterase activity (increased in neural tube defects) and karyotype of fetal skin cells. Although testing for HIV can be done any time, it is most appropriate at the first prenatal visit, because earlier onset of prophylaxis with acquired immune deficiency syndrome (AIDS) drugs reduces the risk of transmission to the fetus significantly. Routine culture for GBS is not recommended because of the high recurrence rate after treatment and the low attack rate to the fetus. Amniocentesis is not a screening procedure and is reserved for those women with a specific indication, such as elevated MSAFP, low MSAFP (risk of Down syndrome), advanced maternal age, and others. A glucose tolerance test may be appropriate if there is a clinical indication for diabetes mellitus: previous macrosomic infant or stillbirth, strong family history of diabetes mellitus, persistent glycosuria, previous gestational diabetes, or elevated random serum glucose concentration.

• Question 609:

  A 23-year-old married woman consults you because she and her husband have never consummated their marriage because she has severe pain with attempts at vaginal penetration. Her pelvic examination is normal except for involuntary tightening of her vaginal muscles when you attempt to insert a speculum. Which of the following conditions would best be treated with the use of vaginal dilators?

  A. primary dysmenorrhea

  B. vaginismus

  C. deep-thrust dyspareunia

  D. anorgasmia

  E. vulvar vestibulitis

  Correct Answer: B

  Vaginismus is the painful, involuntary spasm of the musculature of the pelvis and lower third of the vagina. It may respond to properly administered dilator therapy, although there is a lack of conclusive evidence. Deepthrust dyspareunia is often the result of pelvic pathology, such as fibroids, endometriosis, ovarian cysts, pelvic adhesions, and others. Anorgasmia is usually a psychological disorder best dealt with by a psychologist or psychiatrist expert in sexual counseling and therapy. Sexual or physical abuse should be considered and the woman questioned about this possibility. Vulvar vestibulitis is an inflammatory condition of uncertain (perhaps multiple) etiology and is usually treated with topical glucocorticoids. Failure of medical therapy may require surgical excision of the affected area.

• Question 610:

  A 35-year-old G3P3 woman has been experiencing bilateral breast pain for the past year. Breast examination and mammography are normal. Conservative measures have failed. Which of the following medications is most likely to bring relief?

  A. clomiphene

  B. tamoxifen

  C. danazol

  D. hydrochlorothiazide

  E. medroxyprogesterone

  Correct Answer: B

  Breast discomfort is a problem premenstrually for many women. Simple palliative measures include administration of vitamin E, 600 units daily, and limiting methylxanthines by eliminating coffee and other caffeine-containing substances, although the mechanism of action is not well understood. Danazol (Danocrine), in doses of 200400 mg daily, is often effective in relieving breast pain. Clomiphene may have estrogenic side effects and worsen breast pain. Many women receiving progesterone note breast discomfort secondary to fluid retention. There is no evidence that diuretics such as hydrochlorothiazide relieve breast pain. In one comparison study, tamoxifen (a selective estrogen receptor modulator) was more effective than danazol.