The 3 study objectives were to estimate the live birth prevalence of all HDFN, Rh factor alloimmunized HDFN only, and clinically severe HDFN; to identify clinically significant risk factors for HDFN; and to determine the rates of clinical outcomes and treatments associated with newborns with HDFN when compared with healthy newborns and other sick newborns. This evidence concerns the gene RHCE and fetal erythroblastosis.