Suppression of Primary Rh-immunization by Anti-Rh

A case is reported in which passively acquired antibody (RhoGAM®) apparently prevented maternal immunization to Rh by a large volume of Rh-positive blood. After a 1,000-ml transfusion of Rh-positive blood into an Rh-negative mother, 59 ml of Rh-immune globulin were administered in fractional doses at 12-hour intervals for eight days. During this time, tests for evidence of mixed agglutination, direct and indirect antiglobulin tests, and the hematocrit value were used to monitor patient response. The dose of Rh-immune globulin administered (17,700 μg), as well as the ratio of Rh antibody (μg) to volume (ml) of administered blood, was 18 to 1, the highest thus far reported, but adverse effects were not noted.