Rh Immune Globulin (Anti-D / RhoGAM) for Prevention of Rh Hemolytic Disease

For decades before RhoGAM, Rh hemolytic disease of the fetus and newborn was one of the most common causes of perinatal death and serious neonatal morbidity in the developed world. The mechanism was well understood by the 1950s: an Rh-negative mother who was exposed to Rh-positive fetal red cells during delivery, miscarriage, or amniocentesis could develop IgG anti-D antibodies. In a subsequent pregnancy with an Rh-positive fetus, those antibodies crossed the placenta, bound to fetal erythrocytes, and caused hemolysis severe enough to cause hydrops fetalis, stillbirth, or neonatal jaundice with kernicterus. In the United States alone, approximately 10,000 fetal or neonatal deaths per year were attributed to the disease before prophylaxis became available.

The idea that passive anti-D administration might suppress the active immune response drew on an established immunological principle: exogenous antibody directed against a foreign antigen can inhibit the recipient's own antibody formation against that antigen. Vincent Freda, an obstetrician, and John Gorman, a physician at Columbia University Medical Center, developed this hypothesis in the early 1960s alongside immunologist William Pollack. To test it, they enrolled male prison volunteers at Sing Sing Correctional Facility, deliberately sensitizing Rh-negative men with Rh-positive red cells and then administering anti-D to determine whether the immune response was blocked.

The Sing Sing trials showed clearly that anti-D given after antigen exposure prevented active sensitization. Clinical trials in postpartum Rh-negative women followed, with anti-D administered within 72 hours of delivery of an Rh-positive infant. The results were consistent: sensitization rates fell from roughly 13 to 14 percent in unprotected women to below 1 percent with prophylaxis. The FDA licensed RhoGAM in the United States in 1968, and the product entered clinical practice rapidly.

Subsequent refinement of the dosing schedule added administration at 28 weeks gestation, after recognition that a small proportion of sensitizations occurred during pregnancy itself, before delivery. The addition of antenatal prophylaxis reduced residual sensitization rates further. Within a decade of widespread use, the incidence of Rh hemolytic disease in countries with functioning antenatal programs had dropped by roughly 90 percent from pre-prophylaxis levels.

Parallel development of anti-D prophylaxis was also underway abroad during the same period, with groups in Liverpool, England, and Winnipeg, Canada, conducting independent trials that reached the same conclusions. Rh hemolytic disease, once requiring intensive management including intrauterine transfusion and exchange transfusion of the neonate, is now rare enough in high-income countries that many obstetricians in training have seen few or no untreated cases. In lower-income settings where anti-D is not consistently available, the disease still causes preventable stillbirths and newborn deaths.