Prenatal diagnosis by fluorescence in situ hybridization on chorionic villus cells: nonsignificance of maternal cell contamination.

We assessed the effect of maternal cell contamination on the sensitivity of prenatal diagnosis by fluorescence in situ hybridization (FISH) on overnight attached mesenchymal chorionic villus cells. Double targets FISHs with X and Y chromosome-specific probes were performed on parallel samples from the same pregnancies: (1) samples of assumed fetal tissue retained during dissection, and (2) samples of suspected maternal tissue discarded during dissection. In the karyotypically male samples the tissue retained during dissection contained 0-3% nuclei with two X-specific signals each. In the tissue discarded from the karyotypically male samples 0-50% of the nuclei had two X-specific signals each. We conclude that given thorough dissection of chorionic villi, the sensitivity of prenatal diagnosis of aneuploidies by FISH on overnight attached samples of this tissue is not critically affected by maternal cell contamination.