SRY gene amplifications and genotypings revealed the occurrence of the hidden maternal decidual cells in 46,XX karyotyped spontaneous abortions: Reports of abnormal karyotypes or normal 46,XY karyotypes of the abortion materials derivated from tissue cultures are mostly addressing the pregnancy loss tissues. The accuracy of the cytogenetic reports of normal 46,XX karyotypes is obscure, as the results may reflect the normal karyotyped female pregnancy losses or the hidden maternal decidual cells covering the cytogenetically normal or abnormal male or female products of conception. In the present study, thirty-eight 46,XX normal karyotyped abortion materials cultivated from villi were re-analysed for excluding maternal cell contamination by using molecular approaches in an accurate algorithm. Abortion materials DNAs were amplified by polymerase chain reaction (PCR) technique in order to search the products of the sex determinating region gene of chromosome Y (SRY). Sixteen out of 38 abortion materials revealed Y-chromosome component (42.1%). Amplification negative DNAs and their parental DNAs were genotyped by using high-polymorphic microsatellite DNA markers to identify the origin of the components of the chromosome X. Maternal chromosome X components were detected in 18 (81.8%). As a result, SRY amplifications and genotypings ascertained the high rate of maternal decidual cells in 46,XX products of conception.