When should an Rh-negative mother receive RhoGAM to prevent erythroblastosis fetalis?

An Rh-negative mother should receive RhoGAM at 26 to 28 weeks' gestation and again within 72 hours after delivery to effectively prevent erythroblastosis fetalis, a condition that can occur if an Rh-negative mother produces antibodies against Rh-positive fetal blood. The administration of RhoGAM at the specified times is crucial because it provides passive immunity to the mother, preventing her immune system from forming antibodies against the Rh factor that may be present in the fetus’s blood.

The timing at 26 to 28 weeks’ gestation is particularly important because it allows the RhoGAM to circulate in the mother’s system before labor, reducing the risk of sensitization if fetal blood cells enter the maternal bloodstream during delivery. The additional dose within 72 hours post-delivery is also vital, as it helps to prevent sensitization from any Rh-positive blood cells that may have mixed with the maternal blood during the birth process. This dual administration approach has been shown to significantly reduce the likelihood of developing severe Rh incompatibility issues in future pregnancies.

In contrast, the other options do not provide effective prophylaxis against erythroblastosis fetalis. Giving RhoGAM only at the time of delivery does not address the potential for antibody