Management of Rh-Negative Mother with Rh-Positive Baby
Give anti-D to the mother only—the baby does not receive anti-D prophylaxis. 1, 2
Rationale for Maternal-Only Administration
Anti-D immune globulin (RhIg) works by suppressing the maternal immune response to fetal Rh-positive red blood cells that enter maternal circulation during delivery. 2 The mechanism involves preventing the mother from developing antibodies that would attack Rh-positive red cells in future pregnancies, not treating the current infant. 2
- The current baby is not at risk because this is typically the first exposure, and the mother has not yet developed anti-D antibodies. 1
- Future pregnancies are the concern—without prophylaxis, the mother would develop antibodies that cause hemolytic disease of the fetus/newborn in subsequent Rh-positive pregnancies. 1
Specific Administration Protocol
Timing is critical:
- Administer RhIg within 72 hours of delivery for optimal effectiveness. 1, 2
- If the 72-hour window is missed, give RhIg as soon as recognized up to 28 days postpartum—delayed administration is less protective but still preferable to none. 1
Standard dosing:
- Give 300 μg (1500 IU) intramuscularly or intravenously within 72 hours of delivering an Rh-positive infant. 1, 2
- Alternatively, 120 μg may be used with testing for fetomaternal hemorrhage exceeding 6 mL of fetal red blood cells. 1
Additional Dose Requirements
Screen for excessive fetomaternal hemorrhage:
- The standard 300 μg dose covers up to 15 mL of fetal red blood cells (approximately 30 mL of fetal blood). 1
- For hemorrhage exceeding this amount, give an additional 10 μg of anti-D for every 0.5 mL of fetal red blood cells beyond the covered amount. 1, 3
- Consider quantitative testing for fetomaternal hemorrhage following placental trauma, abruption, or abdominal trauma. 1, 3
Verification Requirements Before Administration
Confirm the following criteria are met: 2
- Mother must be Rh-negative
- Mother must not already be sensitized (no existing anti-D antibodies)
- Baby must be Rh-positive
- Baby should have a negative direct antiglobulin test
Critical Pitfall to Avoid
Do not administer anti-D to the infant—this is a maternal prophylaxis intervention only. The baby receives no benefit from anti-D administration and it is not indicated. 1, 2 The protection is entirely for future pregnancies by preventing maternal sensitization during the current delivery.
Effectiveness Data
Without postpartum RhIg, the rate of maternal sensitization is 12-13%. 2, 4 With proper postpartum administration within 72 hours, this drops to 1-2%. 1, 2, 4 When combined with the antenatal dose given at 28 weeks, sensitization rates decrease further to 0.1-0.2%. 1