Reliability of Fetal Sex Determination Using Maternal Plasma

To determine the diagnostic accuracy of noninvasive fetal sex determination in maternal plasma. 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. 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. Noninvasive fetal sex determination in maternal plasma is highly reliable and clinically applicable. III.