Prenatal Platelet Genotyping for Neonatal Alloimmune Thrombocytopenia.

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To reveal the prevalence of maternal alloimmunization to platelet antigens (HPA) and the incidence of neonatal alloimmune thrombocytopenia (NAT), 10,000 maternal sera were tested for the presence of anti-HPA antibodies using the Mixed Passive Haemagglutination. Ninety-six anti-HPA were found ; anti-HPA-4b, -5a, -5b and anti-Nak^a in 23,2,70 and one pregnant women, respectively.Optimal management of NAT requires the determination of fetal HPA status as early as possible. We explored the feasibility of fetal HPA-4 genotyping by amplification of DNA from amniotic cells using sequence specific primers-polymerase chain reaction (PCR-SSP). Three babies in which fetal HPA-4 type from amniotic fluid cells was completely concordant with type using the blood of these infants studied. Two fetuses were shown to be homozygous PHA-4a/a, and had normal platelet counts. The third fetus was heterozygous HPA-4a/b incompatible with maternal antibody, and developed thrombocytopenia. These findings suggest that HPA-4 genotyping can be reliable determinied from amniotic fluid by DNA amplification.