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Vasa previa — USMLE Step 2 CK MCQ

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ModerateObstetrics & GynecologyVasa previaUSMLE Step 2 CK

A 37-year-old White woman comes to the emergency department because of pelvic symptoms or pregnancy-related concerns. History and focused examination are notable for ruptured membranes followed by painless bleeding and fetal bradycardia. Temperature is 101.5°F (38.6°C), blood pressure is 82/48 mmHg, pulse is 132/min, respirations are 28/min, and oxygen saturation is 90% on room air. Physical examination confirms the key finding and shows no unrelated abnormality that would better explain the presentation. Focused laboratory studies and initial testing support the clinical pattern described in the stem. Which of the following is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — Vasa previa

The vignette describes Vasa previa, supported by ruptured membranes followed by painless bleeding and fetal bradycardia. Vasa previa is the single best answer because it matches the diagnostic or management priority in this clinical setting. The other choices are plausible alternatives in related presentations, but they do not best fit the timing, findings, and guideline-directed approach described here.

Reference: SMFM Consult Series on Vasa Previa