Clinical applications of cell-free fetal DNA from maternal plasma

OBJECTIVE: To describe our clinical experience with detection and analysis of cell-free fetal DNA derived from maternal plasma for prenatal sexing and fetal rhesus-D typing. METHODS: Real-time quantitative polymerase chain reactions (PCRs) of rhesus-D sequences and the SRY gene were validated and offered to patients with an enhanced risk for sex-linked fetal pathology and patients with rhesus-D antibodies. RESULTS: In die validation group, 72 samples were analyzed. Sensitivity of the rhesus-D real-time quantitative PCR in maternal plasma was 100% (95% confidence interval [CI]91.8%, 100%) and specificity was 96.6% (95% CI 82.2%,99.9%). Sensitivity of the SRY real-time quantitative PCR was 97.2% (95% CI 85.5%, 99.9%), and specificity was 100% (95% CI 88.1%, 100%). The technique was used successfully in a clinical setting in 24 women. Overall, invasive tests were avoided in 41.7% of these patients. CONCLUSION: Detection of cell-free fetal DNA from maternal plasma is a reliable technique that can substantially reduce invasive prenatal tests. (C) 2004 by The American College of Obstetricians and Gynecologists.