In the context of Anti-D immunoglobulin, when should prophylaxis be administered during pregnancy?

Prophylaxis with Anti-D immunoglobulin is recommended to prevent Rh sensitization during pregnancy in Rh-negative women who are carrying an Rh-positive fetus. The most critical times for administration are during the third trimester and after delivery.

The optimal time to administer Anti-D immunoglobulin is at 28 weeks of gestation for Rh-negative women, as this timing helps ensure that any fetal Rh-positive red blood cells that may have entered the maternal circulation are neutralized before any potential sensitization can occur. Additionally, postpartum administration is essential to further reduce the risk of sensitization if the baby is found to be Rh-positive.

Administering Anti-D immunoglobulin at 20 weeks or at conception is not standard practice and does not align with established guidelines, as the likelihood of fetal-maternal hemorrhage before 28 weeks is lower and doesn't warrant prophylaxis at that early stage. The administration at delivery is also important, but it should not be the only time this intervention occurs, as antepartum prophylaxis at 28 weeks is crucial for successful prevention of sensitization.