An Rh-negative primigravida delivers a Rh-positive baby. Her indirect Coombs test at 28 weeks was negative. The Kleihauer-Betke test after delivery shows 0.8% fetal cells in maternal blood. What dose of anti-D immunoglobulin should be administered?

• A 150 mcg (750 IU) is sufficient as the standard postpartum dose
• B No anti-D needed as the fetal cell percentage is <1%
• C 300 mcg (1500 IU) single dose covers up to 30 mL of fetal blood exposure ✓
• D 600 mcg (3000 IU) because the Kleihauer-Betke result indicates massive feto-maternal hemorrhage

Explanation

A Kleihauer-Betke result of 0.8% fetal cells in maternal blood corresponds to approximately 40 mL of fetal whole blood (0.008 × 5000 mL maternal blood volume = ~40 mL). A standard dose of 300 mcg (1500 IU) anti-D immunoglobulin covers up to 30 mL of fetal RBCs or ~60 mL of fetal whole blood. Since 40 mL of fetal blood falls within this range, a single 300 mcg dose is adequate. Massive feto-maternal hemorrhage (>30 mL fetal RBCs) would require additional doses. In India, the dose is 300 mcg within 72 hours of delivery.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.