Anti-RhD IgG serum concentration (mean ± SD) after administration of anti-RhD immune globulin. Rhophylac was administered both intravenously and intramuscularly at the standard dose of 1500 IU (300 μg) anti-RhD as determined by the AutoAnalyzer. MonoRho was administered both intravenously (IV) and intramuscularly (IM) at different doses defined by measurement of purified anti-RhD antibody (optical density [OD], 280 nm). Anti-RhD IgG levels in serum were measured using a sensitive FACS assay as described in “Patients, materials, and methods.”