A 24-year-old primigravida at 36 weeks gestation has rupture of membranes followed immediately by painless vaginal bleeding and a sudden fall in the fetal heart rate to 80 bpm with sinusoidal pattern. The uterus is soft and non-tender. Which of the following is the most likely diagnosis?

• A Placental abruption
• B Cord prolapse
• C Vasa previa ✓
• D Marginal placenta previa

Explanation

Vasa previa involves fetal vessels running over the internal os, unsupported by Wharton jelly or placental tissue. When membranes rupture these vessels tear, causing rapid fetal exsanguination and acute fetal bradycardia out of proportion to maternal blood loss. Abruption is painful with a tender, tense uterus, and marginal previa bleeds are maternal, not associated with this abrupt fetal collapse.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.