[Optimum time of maternal blood sampling for prenatal diagnosis with fetal cells].

To investigate the optimum time of maternal blood sampling for prenatal diagnosis with fetal cells.,Zinc-finger protein gene on Y-chromosome (ZFY) sequences were examined by nested polymerase chain reaction in the peripheral blood of 41 pregnant women.,19 pregnant women carrying male fetuses, and another 22 women found to carry female fetuses. Among the 19 pregnant women, ZFY gene were detected in 1/19 (5.3%) cases before the 6th gestational weeks, in 13/19 (68.4%) before the 11th weeks, and in 18/19 (95.0%) before the 14th weeks. The results of this study clearly demonstrated that the gender prediction obviously increased along with the gestational weeks. ZFY gene was not detected in the blood of another 22 women carrying female fetuses. The final accuracy of 97.8% (40/41) was attained in all cases.,The optimum time of maternal blood sampling is at the 14th week, and the appearance of fetal cells in maternal blood was quite case-variable from the 6th to 14th weeks.