Abstract： Objective To assess the frequency and significance of maternal cell contamination (MCC)in the invasive prenatal diagnosis,and to analysis the MCC effect on prenatal diagnosis results.Methods Totally 519 amniotic fluid samples from second trimester pregnancy,57 chorionic villus samples from first trimester pregnancy,and 576 blood samples from corresponded pregnant women were collected and genotyped by Promega PowerPlex 16 system.MCC was determined according to the genotyping results.Karyotypic and molecular diagnosis results were contrasted between MCC and non-MCC specimen of the same fetal.Results MCC presented in 3.1％(16/519)uncultured amniotic fluid,1.3％(7/519)cultured amniotic fluid and 5％(3/57)villi specimens.In the study of fetal karyotype,MCC had no significant effect on normal female fetus;but for male fetus and abnormal female fetus,there were risk of erroneous results of mosaics.As to molecular diagnosis,MCC resulted in more complex effects for the different diagnostic methods.And 10％ MCC had led to misdiagnosis.Conclusions For the prenatal cytogenetic tests,MCC should be excluded when there were mosaicism karyotype results or suspicious MCC of chorionic villi samples.The effects of MCC had more seriously impact on prenatal molecular testing,which suggesting the recommend regular identity test for MCC should bc carried out.