RESUMO
AIM: This study evaluates the use of cell-free fetal DNA in the plasma of RhD-negative women for noninvasive early detection of fetal RhD status and gender. METHOD: Ninety RhD-negative pregnant women were enrolled in the study. Amplification by real-time polymerase chain reaction (PCR) of RhD gene sequences and SRY gene sequence for the diagnosis of fetal RhD and sex was performed. RESULTS: Among 90 RhD-negative women, according to phenotypic diagnosis, there were 61 RhD-positive and 29 RhD-negative fetuses. Also, 37 were males and 53 were females. In the first trimester, the sensitivity and the diagnostic accuracy of real-time PCR for Rh genotyping were 93.5% and 91.1%, increasing to 100% and 97.78%, respectively, in the second trimester. With regard to fetal sex determination, in the first trimester, PCR results had a sensitivity of 95.2% and a diagnostic accuracy of 97.8%, both increasing to 100% in the second trimester. CONCLUSION: The use of cell-free fetal DNA in prenatal noninvasive early detection of fetal RhD status and gender by real-time PCR is highly sensitive and accurate as early as the 11th week of gestation for RhD status and the 7th week of gestation for fetal sex.