A Rh-negative woman who is unsensitised delivers a Rh-positive baby. She did not receive antenatal anti-D prophylaxis. Anti-D immunoglobulin should be administered within what time frame post-delivery to be effective?
- A Within 24 hours
- B Within 72 hours ✓
- C Within 7 days
- D Within 14 days
Correct answer: B. Within 72 hours
Explanation
Anti-D immunoglobulin must be administered within 72 hours of delivery (or any sensitising event) to an unsensitised Rh-negative woman to prevent primary immunisation. The window is based on the time needed to clear fetal RBCs from maternal circulation before an immune response mounts. If not given within 72 hours, it may still provide partial protection if given up to 10 days, but 72 hours is the standard recommended maximum. The standard postnatal dose is 300 mcg IM (if fetal blood group is Rh-positive).
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.