Rho(D) immune globulin is administered to an Rh-negative mother to prevent alloimmunization at which times?

Rho(D) immune globulin is administered to an Rh-negative mother to prevent alloimmunization at which times?

• A. At 12 weeks gestation
• B. Only after delivery
• C. At 28 weeks gestation and within 72 hours after birth if the newborn is Rh-positive
• D. Only if the mother is Rh-positive

Answer: (C)

Rho(D) immune globulin prevents the Rh-negative mother from becoming sensitized to Rh-positive fetal red cells by neutralizing those cells in the maternal circulation before she mounts an antibody response. The timing is chosen to cover both pregnancy and delivery: give it at 28 weeks gestation to protect against fetomaternal hemorrhage later in pregnancy, and administer again within 72 hours after birth if the newborn is Rh-positive to prevent sensitization from the delivery process. Giving it at 12 weeks would miss the window when fetal blood can cross into maternal blood later in pregnancy, and waiting only until after delivery wouldn’t prevent exposure that occurs during pregnancy. This strategy is for Rh-negative mothers; an Rh-positive mother wouldn’t need it.

Rho(D) immune globulin prevents the Rh-negative mother from becoming sensitized to Rh-positive fetal red cells by neutralizing those cells in the maternal circulation before she mounts an antibody response. The timing is chosen to cover both pregnancy and delivery: give it at 28 weeks gestation to protect against fetomaternal hemorrhage later in pregnancy, and administer again within 72 hours after birth if the newborn is Rh-positive to prevent sensitization from the delivery process. Giving it at 12 weeks would miss the window when fetal blood can cross into maternal blood later in pregnancy, and waiting only until after delivery wouldn’t prevent exposure that occurs during pregnancy. This strategy is for Rh-negative mothers; an Rh-positive mother wouldn’t need it.