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
38) Severe preeclampsia • This patient has new-onset HTN (systolic BP ≥140 or diastolic BP ≥90) with severe features (eg, thrombocytopenia, visual or cerebral sxs)
39) Atelectasis • Surgery/Post-op care often → atelectasis + fever • Lack of erythema at incision site r/o wound infection
40) Spontaneous disappearance of the lesions within 1 week • Herpes simplex virus (HSV) generally resolves within a week of lesion development • HSV recurrences become less frequent over time
41) Mastitis • Mastitis - Unilateral, localized tenderness and erythema + fever
• Non-fluctuant nature R/O breast abscess
42) Decreased external urethral sphincter tone • ↑ abdominal pressure (eg, cough, sneeze) → urine loss (stress incontinence)
• Multiparity or previous pelvic surgery → laxity of pelvic floor musculature → urethral sphincter insufficiency
43) Uteroplacental insufficiency
• The fetus is 33 weeks but fetal size is consistent with 30 week gestation = IUGR (uteroplacental insufficiency)
• Lupus → hyalinization of blood vessels → uteroplacental insufficiency
• U/S at 20 weeks showed a fetus with normal anatomy (the kidneys develop before this, thus renal agenesis would have been identified at that time)
44) Propylthiouracil therapy
• PTU is preferred treatment in thyroid storm because it inhibits T4 → T3 conversion
• For treating general hyperthyroidism, PTU is preferred for first trimester, Methimazole is preferred for second/third trimester (there is limited conflicting data on these drugs, and neither is absolutely contraindicated - it's a poor/old question)
45) Interstitial cystitis
• This patient has pain with urination (worse with bladder distention, improves upon urination) and bladder tenderness (anterior vaginal wall tenderness)
• U/A is within normal limits - rules out UTI
• No menorrhagia, dysmenorrhea - rules out adenomyosis
• No dysmenorrhea, dyschezia, or dyspareunia - rules our endometriosis
46) Type 2 diabetes mellitus • ↑ sugar → overgrowth of yeast (particularly in the vagina)
47) Trimethoprim-sulfamethoxazole
• Prophylactic treatment is advocated for women with ≥2 UTIs in 6 months, or ≥3 UTIs in 12 months
• Use of TMP/SMX is reported to be effective and well tolerated, but does raise concerns about antimicrobial resistance
48) Normal postoperative course
• This patients regional LAD and pain at incision site are normal post-op sxs
• Incisional seroma → collection/pocket of fluid (not found in this patient)
49) Abruptio placentae • Classic presentation: 3rd trimester sudden-onset bleeding, abdominal/back pain, high-frequency low-intensity contractions, and hypertonic/tender uterus
50) Chorioamnionitis • Intraamniotic infection (chorioamnionitis) is diagnosed with maternal fever, plus
one or more of the following: fetal tachycardia (>160), maternal leukocytosis, or purulent amniotic fluid
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