Noninvasive pre-natal diagnosis of sex by maternal cell-free plasma fetal DNA analysis
Fetal sexing from maternal plasma is aimed at early determination of fetal sex, and it is possible to detect in the maternal plasma specific alleles of the fetus, which are inherited paternally. In this case, specific Y chromosome sequences are amplified by PCR. This PCR technique is a useful tool for determining fetal sex, with no risk to the fetus. We determined fetal sex by molecular sexing technique at different gestational stages and compared the results with obstetric ultrasound information, in pregnant women between the 8th and 13th weeks of gestation, who were over 18 years of age. Among the 32 samples collected, 21 were females and 11 were males. Four samples showed false negative results, i.e., the Y chromosome DNA was not detected; however the fetus was male. All results incompatible with true fetal sex were collected from pregnant women at the 8th gestational week. In all four samples, the PCR failed to detect the Y chromosome. The determination of fetal sex from the 9th gestational week on had a satisfactory sensitivity index. The sensitivity and specificity of the tests increase with gestational age, making the test safe and with low probability of false negatives. The maternal cell-free plasma noninvasive test proved accurate for sex detection; it can be considered a practical alternative to traditional invasive diagnostic procedures.