Reliability of Fetal Sex Determination Using Maternal Plasma

OBJECTIVE: To determine the diagnostic accuracy of noninvasive fetal sex determination in maternal plasma. METHODS: All consecutive patients for whom fetal sex determination in maternal plasma was performed in our laboratory from 2003 up to 2009 were included in the study. Real-time polymerase chain reaction was performed for the SRY gene and multicopy DYS14 marker sequence. A stringent diagnostic algorithm was applied. In the case of a positive result for both Y chromosome-specific assays, a male-bearing pregnancy was reported. In the case of a negative result, the presence of fetal DNA was ascertained through the use of 24 biallelic insertion/deletion polymorphisms or paternally inherited blood group antigens. Only if the presence of fetal DNA was confirmed was a female-bearing pregnancy reported. Results were compared with the pregnancy outcomes. RESULTS: A total of 201 women were tested. The median gestational age was 9 0/7 weeks (interquartile range 8 0/7 to 10 0/7 weeks). In 189 of 201 cases (94%), a test result was issued; in 10 cases, the presence of fetal DNA could not be confirmed; in two cases, an early miscarriage was observed. Pregnancy outcome was obtained in 197 cases, including 105 male-bearing and 81 female-bearing pregnancies and 11 miscarriages. Sensitivity and specificity of the test were 100% (95% confidence intervals 96.6-100% and 95.6-100%, respectively). In all 10 cases in which the presence of fetal DNA could not be confirmed, a female was born. CONCLUSION: Noninvasive fetal sex determination in maternal plasma is highly reliable and clinically applicable. LEVEL OF EVIDENCE: III.