A Rh-negative woman delivers a Rh-positive baby. Kleihauer-Betke test reveals 0.3% fetal cells in maternal blood. Calculated fetal-maternal hemorrhage is approximately 15 mL of fetal blood. How many doses of standard anti-D immunoglobulin (300 mcg) are required?
- A Two doses (600 mcg)
- B Three doses (900 mcg)
- C One dose (300 mcg) ✓
- D One dose is insufficient; direct Coombs test is needed first
Correct answer: C. One dose (300 mcg)
Explanation
Each 300 mcg dose of anti-D immunoglobulin covers up to 30 mL of fetal blood (or 15 mL fetal red cells). A fetal-maternal hemorrhage of 15 mL of fetal blood is well within the coverage of a single 300 mcg dose. Additional doses are required only if FMH exceeds 30 mL of fetal blood. The Kleihauer-Betke test is used to quantify FMH and guide anti-D dosing.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.