Rho(D) Immune Globulin (RhoGAM): Mechanism, Indications, and Prevention of Hemolytic Disease of the Fetus and Newborn

Pathophysiology of Rh Alloimmunization

An Rh-negative mother (lacking D antigen) carrying an Rh-positive fetus (inherited from Rh-positive father) may be exposed to fetal red cells during pregnancy or delivery. Her immune system recognizes the D antigen as foreign, producing anti-D IgG antibodies. These cross the placenta in subsequent pregnancies, destroying fetal Rh-positive red cells → hemolytic disease of the fetus and newborn (HDFN)—causing anemia, hyperbilirubinemia (kernicterus risk), hydrops fetalis, or fetal demise.

RhoGAM: Mechanism of Action

Rho(D) immune globulin is a purified polyclonal anti-D IgG derived from Rh-negative donors hyperimmunized with Rh-positive cells. Administered prophylactically, it binds fetal Rh-positive cells in maternal circulation before they can stimulate active maternal antibody production—immune cloaking.

Standard Administration Protocol

• Routine antenatal: 300 µg (1500 IU) IM at 28 weeks gestation.
• Postpartum: 300 µg IM within 72 hours of delivery if infant is Rh-positive (confirmed by cord blood typing).
• Additional indications: Miscarriage, abortion, ectopic pregnancy, amniocentesis/CVS, external cephalic version, abdominal trauma, antepartum hemorrhage, placental abruption—all within 72 hours.

Safety and Efficacy

• Reduced HDFN incidence from ~10–15% to <0.1% in at-risk pregnancies.
• Excellent safety profile: local reactions, rare low-grade fever; no viral transmission (viral inactivation steps in manufacturing).
• Does not affect current pregnancy; protects future pregnancies.

RhoGAM is a landmark preventive intervention in obstetrics, transforming Rh alloimmunization from a leading cause of perinatal mortality to a rare, manageable condition.