Discordance between fetal RhD typing using molecular methods and neonatal typing with serology

Polymerase chain reaction (PCR)-based genotyping on amniotic fluid in an RhD-negative alloimmunized woman predicted an RhD-negative fetal blood type. The neonate was RhD-positive and developed hemolytic disease. Discrepant results were also observed on paternal testing. PCR analysis with a different set of primers correctly predicted the RhD-positive fetal and paternal blood type. Use of more than one set of primers and parental testing can avoid some of the problems associated with use of PCR genotyping.