NBME OB/GYN Form 1 - Answers & Explanations

Updated: Jul 28, 2020

1) Cephalopelvic disproportion Second stage arrest of labor (no fetal descent after pushing for ≥3 hours (nulliparous) or ≥2 hours (multiparous)

• The optimal fetal position is occiput anterior; If the fetus is in occiput anterior, the most likely cause of second stage arrest of labor is cephalopelvic disproportion Montevideo units (MVU) = mmHg (60) x # of contractions in 10 mins (5) = 300 (MVU ≥ 200 is adequate)

2) Primary dysmenorrhea Crampy lower abdominal and back pain during menses with a normal examination Tx: NSAIDs if sexually inactive, OCPs if sexually active

3) Staphylococcus aureus Toxic shock syndrome likely due to prolonged tampon use → systemic inflammatory response to toxic shock syndrome toxin-1, an exotoxin that acts as a superantigen

4) Fetal ultrasonography This patient has received no prenatal care in the past. Placenta previa needs to be ruled out (painless bleeding that can otherwise be Asx)

Placenta previa must be ruled out prior to a digital exam

5) Submucosal Submucosal fibroids are closer to the endometrial lining, and thus are more prone to bleed

6) Oral contraceptive therapy and a second pelvic examination in 6 weeks Simple cysts in premenopausal women usually resolve on their own; hormonal contraceptives inhibit ovulation and thus prevents the formation of new cysts

7) Flagellated protozoa Trichomoniasis is characterized by thin yellow-green discharge and a vaginal pH >4.5 Tx: Metronidazole for patient and sexual partner

8) Gastroschisis Extrusion of abdominal contents, typically to the right of the umbilicus

Not covered by peritoneum or amnion

9) Breast engorgement

• Engorgement - Bilateral symmetric fullness, tenderness and warmth (this patients lack of breastfeeding → engorgement)

• Mastitis - Unilateral, localized tenderness and erythema (additionally, this patient is not breastfeeding, so the likelihood of her getting mastitis is low)

10) Autosomal dominant Achondroplasia has an AD inheritance pattern

11) Normal pregnancy Normal to have implantation bleeding in 1st trimester Placenta previa usually presents with sudden and profuse vaginal bleeding after 28 weeks of gestation

12) Hormone therapy

HRT → ↑ risk of endometrial and breast cancer

13) Hematocolpos This adolescent girl likely has an imperforate hymen - amenorrhea and cyclic lower abdominal pain with bulging vaginal mass (hematocolpos)

14) Reassurance This patient likely has Mittelschmerz, transient mid-cycle ovulatory pain that may mimic appendicitis Reassurance is indicated once acute pathology is excluded

15) Preterm labor and delivery This patient has a Hx of preterm labor (→ ↑ risk of future preterm labor)

16) Ureterolithiasis Flank pain radiating to the groin is consistent with lithiasis No gross hematuria, but there could be microscopic hematuria indicative of lithiasis Fever would be present if this patient had pyelonephritis

17) Osteoporosis No withdrawal bleeding = absent/low estrogen

Estrogen deficiency → ↑ risk of osteoporosis

18) Hemoglobin electrophoresis The physiological anemia of pregnancy can exacerbate the anemia from thalassemia

19) Menarche is imminent

Thelarche → Pubarche → Menarche (follows pubic hard development)

20) Admission to the hospital for intravenous hydration and parenteral antiemetic therapy

This patient likely has Hyperemesis Gravidarum (HG)

HG tx: IV hydration + parenteral antiemetic therapy; Patient is unable to keep solids or liquids down → must be admitted for IV hydration

The presence of ketones helps to differentiate HG from gestational N/V

21) Appendicitis Fever + leukocytosis + right-sided abdominal pain Hematuria and pyuria may occur if the inflamed appendix is close to the bladder or ureter

22) Cervical trauma Cervix is highly vascularized during pregnancy and can bleed more easily from trauma (eg, intercourse)

23) Fine-needle aspiration biopsy of the cyst Biopsy (often U/S guided) is required to confirm the diagnosis of a palpable mass FNA may be used for cystic/small masses; Core biopsy is used for solid masses

24) Hypoestrogenic state Hypoestrogenism → ↓ blood flow & ↓ collagen → ↓ epithelial elasticity and subsequent atrophy → thin, dry, easily denude urogenital epithelium → ↑ susceptibility to injury → vaginal/vulvar bleeding with minimal manipulation

25) Increased 5α-reductase activity

• Excessive hair growth in the absence of lab abnormalities suggests ↑ 5α-reductase activity (converts testosterone into DHT)

• Aromatase converts testosterone into estrogens (this patient has normal lab values)

26) Intravascular injection of anesthetic • Inadvertent intravascular injection of Anesthetic → toxicity → tinnitus & metallic taste (from lidocaine), ↑ HR & BP (from epinephrine)

27) Anovulation

• Irregular periods suggest anovulation → ↑ unopposed estrogen → endometrial hyperplasia

• ↑ BMI → aromatization of androgens to estrogen

28) Follicle-stimulating hormone

• This patient likely has Turner syndrome (hypergonadotrophic hypogonadism)

• If a patient with primary amenorrhea doesn’t have secondary sexual characteristics, the next best step is to measure FSH & LH levels

• GnRH is not a systemic hormone (inside hypophyseal portal blood system)

29) Suction and curettage This patient likely has a complete molar pregnancy (uterus size > gestational age, ↑↑↑ β-hCG); lack of fetal parts distinguishes from partial molar pregnancy

• Molar pregnancy is treated with D&C and the downtrend of β-hCG must be followed. Additionally, patient must be on a reliable contraceptive so that she does not become pregnant while here β-hCG downtrend is being followed

• Methotrexate is Tx for ectopic pregnancy if the patient is stable

• Misoprostol is a PGE analog used for abortion (not safe for use with molar pregnancy)

30) Decreased protein content in breast milk

• OCPs should not be given before 6 weeks postpartum

• OCPs given before 3 weeks postpartum → ↑ risk of DVT

• OCPs given before 6 weeks postpartum → ↓ protein content of breast milk (progesterone inhibits α-lactalbumin, the major protein found in breast milk)

31) Administration of Rh (D) immune globulin • This patient is Rh ⊖ and unsensitized (⊖ antibody test). This patient should be given Rhogam every time she comes into contact with fetal blood to keep her unsensitized

32) Punch biopsy of the affected areas

• This patient most likely has Lichen sclerosis

• Punch biopsy should be used to exclude malignancy

• Tx: potent corticosteroid ointment (this question asked for the most appropriate next step, not the best treatment option)

33) Congenital uterine anomalies

• This patient likely has some agenesis on the right. Development of a left sided paramesonephric (mullerian) duct → unicornuate uterus

• Palpable uterus on physical exam r/o Mullerian agenesis

34) Neisseria gonorrhoeae • Gram ⊖ intracellular diplococci • Chlamydia is difficult to stain/visualize

35) Umbilical cord compression

• This patients membranes have ruptures → loss of amniotic fluid → cord compression and variable decelerations

• Variable decelerations are due to cord compression, oligohydramnios, or cord prolapse

36) Testosterone • Sertoli-Leydig (Arrhenoblastoma) - testosterone producing tumor of the ovary

• DHEAS is produced by adrenal glands

37) Pregnancy This patient hasn’t had her period in 6 weeks, her uterus is enlarged, and she uses condoms inconsistently Thin clear vaginal discharge is physiologic in pregnancy