Critical Clarification: Question Contains an Error
You do NOT give RhoGAM to Rh-POSITIVE women. RhoGAM is ONLY indicated for Rh-NEGATIVE women. This is a fundamental contraindication clearly stated in the FDA label 1.
Assuming you meant to ask about Rh-NEGATIVE pregnant women, here is the answer:
RhoGAM Administration Timing in Rh-Negative Pregnant Women
Standard Dosing Schedule
For routine uncomplicated pregnancy in Rh-negative women, RhoGAM is administered at 26-28 weeks gestation (antepartum prophylaxis) and again within 72 hours after delivery if the newborn is Rh-positive (postpartum prophylaxis). 1
Key Timing Points:
Antepartum (During Pregnancy):
- Primary dose: 26-28 weeks gestation - This is the standard timing recommended by FDA labeling 1
- If given before 26-28 weeks for any reason, maintain prophylaxis by repeating every 12 weeks 1
- If delivery doesn't occur within 12 weeks of the 28-week dose, give a second antepartum dose to maximize protection 1
Postpartum (After Delivery):
- Within 72 hours of delivery if baby is Rh-positive 1
- May be withheld if delivery occurs within 3 weeks of last antepartum dose, BUT must test for fetal-maternal hemorrhage >15 mL 1
- If not given within 72 hours, give as soon as recognized up to 28 days post-delivery 2
Additional Indications Requiring RhoGAM
First Trimester (<12 weeks):
- Minimum 120 μg dose for threatened/spontaneous/induced abortion 1
- Ectopic pregnancy 1
- The 2024 SMFM guideline recommends offering RhoGAM even for events <12 weeks when feasible, though this remains debated 3
After 12 Weeks Gestation:
- 300 μg dose for threatened pregnancy loss with continuation 1
- Pregnancy termination (spontaneous or induced) 1
Any Gestational Age - Sensitizing Events:
- Amniocentesis: 300 μg 1, 2
- Chorionic villus sampling: 120 μg if <12 weeks, 300 μg if ≥12 weeks 1, 2
- Cordocentesis: 300 μg 1, 2
- Abdominal trauma 1
- External cephalic version 2
- Placental abruption 2
- Placenta previa with bleeding 2
Critical Clinical Pearls
Timing is crucial: The 72-hour window is standard, but later administration (up to 28 days) still provides some benefit 2
The mid-trimester dose reduces alloimmunization from 1.8% to 0.1-0.2%, while postpartum dosing alone reduces it from 13-17% to 1-2% 3
Common pitfall: Nearly half of women may have undetectable anti-D at delivery when prophylaxis is given at 28 weeks, especially if delivery occurs >12 weeks later 4. This supports the recommendation for a second dose if delivery is delayed.
Fetal RBCs express D-antigen as early as 6 weeks gestation 3, 5, creating theoretical risk throughout pregnancy, though fetomaternal hemorrhage increases with advancing gestation (7% first trimester, 16% second trimester, 29% third trimester) 5.