All pregnant women should be tested at the time of the first pre-natal visit for ABO blood group and Rh-D type and screened for the presence of erythrocyte antibodies. These laboratory assessments should be repeated in each subsequent pregnancy. Repeated anti-body screening is also recommended before administration of anti-D immunoglobulin at 28 weeks of gestation, post-partum, and the time of any event in pregnancy. Patients who are weak-D positive are not at risk for isoimmunization and should not receive anti-D immunoprophylaxis.
Any antibodies potentially associated with fetal hemo-lysis found during this routine screening are further eval-uated based on the strength of the antibody response, which is reported in titer format (1:4, 1:8, 1:16, etc.), with higher numbers indicative of a more significant antibody response. Although often encountered during the process of antibody screening, anti-Lewis and Anti-I antibodies are not associated with fetal hemolytic disease, and there-fore are not evaluated further.