A Rh-negative mother delivers an Rh-positive infant. When should Rho(D) immune globulin be given?

• A. Within 72 hours after birth
• B. Within 24 hours after birth
• C. During prenatal period only
• D. Any time within first week postpartum

Answer: (A)

Rho(D) immune globulin prevents the Rh-negative mother from forming antibodies to the Rh factor by binding any Rh-positive fetal red cells that enter her circulation during delivery. This prophylaxis is given after exposure to Rh-positive fetal blood, with a standard window of up to 72 hours after birth to catch the feto-maternal hemorrhage that occurs during delivery. Administering it within 72 hours protects future pregnancies from alloimmunization; giving it earlier is acceptable but waiting longer than 72 hours increases the risk of sensitization. Providing it only during the prenatal period would miss the postpartum exposure at birth, and waiting a full week postpartum is less effective. Thus, the best timing is within 72 hours after birth.