Noninvasive determination of fetal RhD status using fetal DNA in maternal serum and PCR

OBJECTIVE: Because prenatal testing of fetal RhD status by amniocentesis ca rries small yet finite risks to the fetus and mother, this study sought to determine whether fetal DNA in maternal serum could be used to detect fetal RhD status by polymerase chain reaction (PCR). METHODS: A retrospective analysis was made of frozen serum specimens from 2 0 sensitized RhD-negative pregnant women (ranging from 15.0 to 36.0 weeks' gestation) who were confirmed by serology at birth to have been carrying Rh D-positive fetuses. Eleven serum specimens from RhD-negative individuals se rved as controls. DNA was isolated from serum and used in two PCR-based met hods to detect a 99 base pair (bp) DNA fragment specific for the RhD gene a nd a 113 pb fragment specific for the RhCE gene as control. RESULTS: Overall, in 14 (70%) of 20 RhD-positive fetuses the 99 base pair R hD-specific PCR product was detected. There was no false positive detection among the 11 control serum specimens. CONCLUSION: The results illustrate the ability to detect fetal RhD sequence s in maternal serum of sensitized women. Moreover, the findings demonstrate that fetal single-gene disorders can be detected prenatally by using DNA i solated only from maternal serum. Copyright (C) 1999 by the Society for Gyn ecologic Investigation.