Prevalence of new maternal alloantibodies after intrauterine transfusion for severe Rhesus disease.

Limited information is published on the frequency of new maternal alloantibodies found in patients treated for isoimmunization. The purpose of this study was to determine the prevalence of additional maternal red cell alloantibodies, found after the initiation of treatment for Rhesus (Rh) disease. A retrospective review of all patients treated for severe Rh disease was undertaken. Rh disease requiring intrauterine blood transfusion was defined as severe. Gravidas with alloantibodies in addition to Rh were included, but those without Rh antibodies were excluded. New alloantibodies were defined as antibodies absent in previous pregnancies and on initial pregnancy screening, and found after the onset of invasive treatment. There were a total of 84 intrauterine blood transfusions performed in 31 gravidas with severe Rh disease. Seven patients (23%) were found to develop additional red cell alloantibodies after treatment during the pregnancy. Induction of additional maternal red cell alloantibodies after treatment for severe Rh disease is relatively common. This may have significant implications for future pregnancies in this high-risk population.