THE ROLE OF HLA ANTIBODIES IN NEONATAL THROMBOCYTOPENIA - A PROSPECTIVE-STUDY

The role of HLA antibodies in neonatal alloimmune thrombocytopenia is controversial. We prospectively studied the sera of obstetric patients at delivery for HLA antibodies and correlated their presence with umb ilical cord blood platelet counts. We studied 493 births at The Johns Hopkins Hospital comprising of 357 African American, 115 Caucasian, an d 21 babies of other racial groups. One hundred and thirty nine mother s had HLA antibodies. Of these HLA alloimmunized mothers, only ten inf ants had platelet counts of 150,000/mu L or less. Three hundred and ei ght mothers with no detectable antibodies gave birth to 27 infants wit h platelet counts of 150,000/mu L or less. Yates corrected Chi square analysis showed no significant relationship between maternal HLA alloi mmunization and baby platelet count (p=0.709). Only 8 of sixty cord se ra from babies of HLA alloimmunized mothers were positive for HLA anti bodies. The HLA cord blood antibody results were then correlated with the neonatal platelet counts. The Fisher's exact test showed no signif icant relationship between the presence of HLA antibodies in cord bloo d samples and neonatal platelet counts (p=0.232). Although one third ( 31%) of mothers have HLA antibodies, neonatal thrombocytopenia is rare ly associated with this finding. However, HLA antibodies can cross the placenta, and in these unusual cases, may be associated with a higher risk of neonatal thrombocytopenia.