A 26-year-old primigravida at 38 weeks with no prior ultrasound presents with heavy vaginal bleeding and fetal distress. Emergency cesarean reveals a velamentous cord insertion with fetal vessels running through the membranes overlying the cervix. The fetus is delivered but is pale with hemoglobin of 6 g/dL. What is the estimated fetal blood volume that can be lost before fetal decompensation occurs in vasa previa rupture?

• A 10% of fetal blood volume
• B 20% of fetal blood volume ✓
• C 30% of fetal blood volume
• D 50% of fetal blood volume

Explanation

The fetus can tolerate loss of approximately 20% of blood volume before decompensation. Fetal blood volume is approximately 80-100 mL/kg. Loss exceeding 20% leads to fetal anemia, hydrops, and death. This explains why even small volumes of bleeding in vasa previa can cause rapid fetal demise.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.