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)