What is the recommended dose and timing of RhoGAM (Rho(D) immune globulin) administration during the prenatal period for an Rh-negative mother?

RhoGAM Administration for Rh-Negative Mothers During Pregnancy

For unsensitized Rh-negative pregnant women, RhoGAM should be administered as a 300 mcg dose at 28 weeks' gestation, followed by another 300 mcg dose within 72 hours after delivery if the infant is Rh-positive. 1, 2, 3

Dosing and Timing Protocol

Standard Prophylaxis Schedule

• At 28 weeks' gestation:

  • 300 mcg (full dose) RhoGAM for all unsensitized Rh-negative women when fetal blood type is unknown or known to be Rh-positive 1
  • Alternative regimen: Two doses of 120 mcg, one at 28 weeks and one at 34 weeks (though the 300 mcg single dose is more common) 3

• After delivery:

  • 300 mcg within 72 hours of delivery if infant is Rh-positive 1, 2
  • Must be administered even if antenatal RhoGAM was given 2

Special Circumstances

• Early pregnancy events (before 12 weeks' gestation):

  • 50 mcg (microdose) within 72 hours of spontaneous or induced abortion 4, 1
  • If 50 mcg dose unavailable, 300 mcg dose should be given 4, 1

• After 12 weeks' gestation:

  • 300 mcg for pregnancy loss, abortion, or other potentially sensitizing events 3

• Delayed administration:

  • If RhoGAM is not given within 72 hours, it should still be administered as soon as possible up to 28 days after the sensitizing event 3

Clinical Considerations

Patient Eligibility

• Only unsensitized Rh-negative women require RhoGAM 1
• Women with "weak D" (Du-positive) do not require RhoGAM 3
• If paternity is certain and father is known to be Rh-negative, RhoGAM may be unnecessary 1, 3

Monitoring for Fetomaternal Hemorrhage

• For standard deliveries, the 300 mcg dose covers up to 15 mL of fetal red blood cells (approximately 30 mL of fetal blood) 3
• Additional RhoGAM may be required for larger fetomaternal hemorrhages 3
• Consider quantitative testing for fetomaternal hemorrhage following events with potential placental trauma (e.g., abdominal trauma, placental abruption) 3

Common Pitfalls to Avoid

1. Failure to administer postpartum dose: Even if antenatal RhoGAM was given at 28 weeks, a postpartum dose is still required if the infant is Rh-positive 2

2. Unnecessary administration: Giving RhoGAM to Rh-positive women or those already sensitized wastes resources and provides no benefit 1

3. Inadequate dosing for large fetomaternal hemorrhage: For hemorrhages exceeding 15 mL of fetal RBCs, additional RhoGAM is needed (10 mcg for each additional 0.5 mL of fetal RBCs) 3

4. Delaying administration beyond 72 hours: While most effective within 72 hours, RhoGAM should still be given up to 28 days after exposure if the 72-hour window is missed 3

5. Confusing blood type with antibody status: A negative antibody screen does not mean the patient is Rh-negative; proper blood typing is essential 1

The Society for Maternal-Fetal Medicine and ACOG both emphasize that prevention of Rh alloimmunization is critical due to its substantial impact on pregnancy outcomes, including hemolytic disease of the newborn, need for fetal transfusion, hydrops, and stillbirth 4, 1.