A woman presents at 35 weeks with painless bright red vaginal bleeding immediately following spontaneous rupture of membranes, accompanied by acute fetal bradycardia. The Apt test is positive. What is the MOST likely diagnosis and the immediate management?

• A Placental abruption — IV fluid resuscitation and monitoring
• B Vasa praevia — immediate emergency caesarean section ✓
• C Show (bloody show) — expectant management
• D Placenta praevia — urgent ultrasound confirmation

Explanation

Vasa praevia occurs when fetal blood vessels (velamentous cord insertion or accessory lobe) cross the internal os unprotected by placenta or cord. Rupture of membranes tears these vessels, causing rapid fetal exsanguination — the blood is FETAL, confirmed by the positive Apt test (fetal haemoglobin is alkali-resistant: pink colour persists with NaOH; adult Hb turns brown). Fetal bradycardia reflects severe fetal anaemia. Perinatal mortality without immediate delivery exceeds 50%; emergency caesarean is life-saving.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.