NBME OBGYN Form 4 - Answers & Explanations

Updated: Nov 16, 2019

1) Increasing her current anticonvulsant medication

• This patients phenytoin concentration is low - the dose should be increased

• Pregnancy → ↑ proteins that bind phenytoin → ↓ phenytoin concentration

• The benefits of treating with phenytoin outweigh the risks, as seizures in mom are dangerous for the baby; additionally, the majority of infants born to women who take phenytoin during pregnancy will not develop fetal hydantoin syndrome

• There is evidence that children exposed to multiple anticonvulsants may be at greater risk for birth defects

2) Hemoglobin electrophoresis

• This patient has microcytic anemia (MCV <80)

• Serum ferritin and iron are normal = no iron deficiency

• Hemoglobin electrophoresis should be used to check for other causes of microcytic anemia (eg, thalassemia)

3) Cervicitis • This patient is afebrile with postcoital bleeding from a new partner • Acute cervicitis commonly presents with postcoital bleeding, mucopurulent discharge, and a friable cervix

4) Normal labor

• Dilation of cervix + painful contractions = labor

• Closed cervix + painless contractions = Braxton-Hicks contractions

• Cervical insufficiency (incompetence) = painless dilation of cervix that can lead to 2nd trimester pregnancy loss

5) Cystic teratoma • Dermoid cysts are seen on U/S as a partially calcified mass (teeth) with multiple thin echogenic bands (hair) • Torsion (twisting of ovary around the infundibulopelvic and utero-ovarian ligaments) → acute-onset severe pain

6) Placement of an IUD

• IUDs are the most effective contraceptives options (~99% efficacy) • This patient is non-compliant with her HTN meds - this makes oral contraceptives (taken daily) and Depo-Provera (injections every 3 months) a poor choice

7) Intraductal papilloma • MCC of unilateral bloody nipple discharge

• No assocaited mass or LAD

8) BMI

• Low body weight, especially < 128lbs (58kg) → ↓ peak bone density → ↑ risk of fracture

• If the patient had suffered a previous fracture (not family history), then that would be the greatest risk factor for an osteoporotic fracture

9) Hysterectomy • Endometrial cancer tx: hysterectomy • Endometrial hyperplasia tx: hysterectomy or progestin

10) Uterine synechiae • Uterine synechiae = Asherman’s syndrome

• D&C → trauma to basal layer of endometrium → intrauterine scars → failure to respond to estrogen

11) Amenorrhea

• Suction and sharp curettage → denuded basal layer of endometrium → Asherman’s syndrome → 2° amenorrhea

• Diagnosis and treatment = hysteroscopy (lyse adhesions)

12) Down syndrome • Down syndrome (trisomy 21) is associated with Duodenal atresia (→ duodenal bubble)

13) Atelectasis • 5 W’s of post-op fever

• Wind (atelectasis) = Post-op day (POD) 1-2 • Water (UTI) = POD 3-5 • Walking (DVT) = POD 4-6 • Wound (infection of surgical wound) = POD 5-7 • Wonder (anything) = POD 7+

• Abdominal surgery (c-section) → pain on deep inspiration → shallow breathing → underutilization of lung bases → atelectasis

14) Vasa previa • Fetal bradycardia is an important distinguishing feature of vasa previa; occurs because hemorrhage is of fetal origin (vs. maternal origin in placenta previa)

15) Uteroplacental insufficiency • Uteroplacental insufficiency → Late decelerations (nadir of deceleration occurs after peak of contraction)

16) Vesicovaginal fistula • Pelvic surgery or irradiation → ↑ risk of vesicovaginal fistula

• Characterized by continuous, painless urine leakage form vagina (→ moist vaginal mucosa)

• Dx: Dye test, cystourethroscopy

17) Stress incontinence

• ↓ urethral sphincter tone and/or urethral hypermobility → stress incontinence → leakage of urine with ↑ abdominal pressure (eg, coughing, lifting, sneezing)

• Tx: Pelvic floor exercises, pessary

18) Placental dysfunction

• Fetal complications of maternal HTN include fetal growth restriction, oligohydramnios, and preterm delivery

• This patient has been receiving prenatal care since 8 weeks gestation - rules out incorrect gestational age

19) Amnioinfusion

• Maternal repositioning (eg, left lateral decubitus) is first-line intervention for variable decelerations as it may reduce cord compression and subsequently improve fetal placental blood flow

• Amnioinfusion is a possible second-line intervention - artificially creates more amniotic fluid which can reduce umbilical cord compression and decrease variable decelerations

20) Chlamydia trachomatis infection

Chlamydia → cervicitis → Inflamed, friable cervix

• Tx: Azithromycin and Ceftriaxone