RESUMO
Objective To establish a noninvasive method for prenatal genetic analysis by using maternal serum and apply the method in fetal sex determination,paternity testing. Methods Samples of maternal serum from 53 pregnant women (11 to 36 weeks of gestation) were collected. The DNA extracted from each sample was amplified by using"Y-PLEX 6" amplification kit .which enabled the simultaneous analysis of six Y-STR loci including DYS393.DYS19.DYS389 II, DYS390, DYS391 and DYS385. The PCR products were detected by using ABI PrismTM 377 Sequencer and genotyped by related analysis software. Results (1) Y-STR specific alleles were detected in the maternal sera of all 29 mothers bearing male babies. Among the six Y-STR loci,specific alleles were detected in 29/29 at DYS393 locus,in 18/29 at DYS19 locus and in 10/29 at DYS390 locus. (2) Y-STR specific alleles were not detected in maternal sera of 24 pregnant women bearing female babies. (3) According to the presence of specific alleles at DYS393 locus and the value of allelic peak height and peak area, the accuracy of fetal sex determination was 100% . (4)The observed Y-STR alleles of each prenatal specimen from pregnant women with male fetuses were the same as the results of their husbands. Conclusion The assay of highly polymorphic Y-STR genotyping system developed by the authors provided a sensitive, accurate and non-invasive method to prenatal diagnosis. Our results demonstrate that fetal sex can be accurately determined and imply that paternity testing could be performed for pregnant women carrying male fetuses.