Obstetrics and Gynecology Flashcards

A 34-year-old woman at 28 weeks' gestation presents with sudden-onset severe headache, visual disturbances, and BP of 158/108 mmHg. Urinalysis shows 3+ proteinuria. Magnesium sulfate is initiated for seizure prophylaxis. Which of the following findings would most reliably indicate magnesium toxicity BEFORE respiratory depression occurs?

Answer: Loss of deep tendon reflexes

Loss of deep tendon reflexes (patellar reflex) is the earliest clinical sign of magnesium toxicity, occurring at serum levels of approximately 7–10 mEq/L. Respiratory depression occurs at higher levels (>12 mEq/L) and cardiac arrest at >15 mEq/L. Monitoring DTRs is the standard bedside method to detect toxicity before it becomes life-threatening. A serum level of 5 mEq/L is within the therapeutic range (4–7 mEq/L) and would not indicate toxicity.

A 27-year-old G2P1 at 32 weeks' gestation is found to have vasa previa on transvaginal ultrasound. She is asymptomatic with no bleeding. Which management strategy is most appropriate at this time?

Answer: Hospitalization, antenatal corticosteroids, and planned cesarean at 34–35 weeks

Vasa previa carries a fetal mortality rate exceeding 50% if undiagnosed at delivery due to fetal exsanguination when membranes rupture. For a prenatally diagnosed, asymptomatic case at 32 weeks, current SMFM guidelines recommend inpatient admission around 30–32 weeks, administration of antenatal corticosteroids for fetal lung maturity, and planned cesarean delivery at 34–35 weeks before labor onset. Immediate delivery at 32 weeks is premature if the patient is stable; outpatient management is unsafe given rupture risk; cerclage has no role in vasa previa management.

A 45-year-old woman undergoes total abdominal hysterectomy with bilateral salpingo-oophorectomy for endometrial cancer. Pathology returns: grade 2 endometrioid adenocarcinoma, myometrial invasion >50%, no cervical involvement, no lymphovascular space invasion, and lymph nodes negative. According to FIGO 2023 staging, what is her stage?

Answer: Stage IB

Under FIGO 2023 staging, Stage IB endometrial cancer is defined as tumor confined to the corpus uteri with invasion of ≥50% of the myometrium, regardless of grade. This patient has no cervical stromal involvement (which would make it Stage II), no adnexal or serosal involvement (Stage IIIA), and no lymph node involvement (Stage IIIC). The absence of lymphovascular space invasion is relevant for risk stratification but does not change the stage. Stage IC does not exist in the FIGO 2023 classification.

A 32-year-old woman with a history of systemic lupus erythematosus (SLE) and antiphospholipid antibody syndrome (APS) presents at 10 weeks' gestation. She has had two prior pregnancy losses at 14 and 16 weeks. She is currently on hydroxychloroquine. What is the MOST appropriate antithrombotic regimen during this pregnancy?

Answer: Low-dose aspirin plus prophylactic-dose LMWH

For obstetric APS (defined by ≥3 unexplained consecutive losses at <10 weeks OR ≥1 unexplained loss at ≥10 weeks in the setting of confirmed antiphospholipid antibodies), the standard of care is the combination of low-dose aspirin (81 mg/day) plus prophylactic-dose LMWH throughout pregnancy and for 6 weeks postpartum. This patient has late losses (14 and 16 weeks) in the setting of APS, meeting criteria for this regimen. Aspirin alone is insufficient for APS-related late losses. Therapeutic-dose LMWH is reserved for patients with a prior thrombotic event, not purely obstetric APS.

A 38-year-old woman presents with 6 months of secondary amenorrhea. FSH is 52 mIU/mL, LH is 38 mIU/mL, estradiol is 18 pg/mL, and prolactin is normal. Karyotype returns 46,XX. She desires future fertility. After counseling about her diagnosis, which statement regarding her long-term prognosis is MOST accurate?

Answer: Spontaneous ovulation and pregnancy occurs in approximately 5–10% of cases

This patient has primary ovarian insufficiency (POI), formerly called premature ovarian failure, based on elevated gonadotropins and low estradiol before age 40. Importantly, POI is not always permanent — unlike surgical menopause, women with 46,XX POI retain intermittent ovarian function in up to 50% of cases, and approximately 5–10% will achieve spontaneous pregnancy over their lifetime. HRT does not restore fertility and does not cause remission; it is used to manage hypoestrogenic symptoms and prevent osteoporosis. Clomiphene is ineffective in the setting of already-elevated gonadotropins. Oocyte donation is the most effective fertility treatment but not the only possible path.

A 29-year-old G1P0 at 39 weeks undergoes induction of labor. After 18 hours of oxytocin infusion, she is 6 cm dilated, 80% effaced, and at 0 station. Fetal heart rate tracing shows Category II decelerations with minimal variability. Intrauterine pressure catheter (IUPC) readings show Montevideo units (MVUs) of 185 over the last 30 minutes. What is the most appropriate next step?

Answer: Increase oxytocin to achieve adequate uterine activity (≥200 MVUs)

Adequate uterine activity is defined as ≥200 Montevideo units over 10 minutes. At 185 MVUs, this patient has not yet achieved adequate contractions, so augmentation failure cannot be diagnosed. The correct step is to increase oxytocin to optimize uterine activity before concluding that labor is arrested. Active phase arrest requires ≥6 cm dilation with membrane rupture AND either no cervical change in ≥4 hours with adequate contractions (≥200 MVUs) or ≥6 hours without adequate contractions. Fetal scalp stimulation is reasonable to assess Category II tracings but does not address the underlying inadequate labor progress. Terbutaline is indicated for tachysystole (>5 contractions in 10 minutes), which is not present here.