Microsatellite analysis reveals a high incidence of maternal cell contamination in 46,XX products of conception consisting of villi or a combination of villi and membranous material

OBJECTIVE: With the use of microsatellite analysis, we sought to determine the incidence of maternal cell contamination in 46,XX products of conception consisting of villi or a combination of villi and membranous material. STUDY DESIGN: Deoxyribonucleic acid from cultured fibroblasts of 46,XX products of conception specimens and a corresponding maternal blood sample were obtained from 31 women. Maternal and fetal genotypes for several highly polymorphic microsatellite markers were compared. RESULTS: Maternal cell contamination was present in 26 (89.7%) of the 29 products of conception specimens from which conclusive results were obtained. The contamination appeared to completely obscure the fetal material in 24 of these specimens. CONCLUSIONS: A significant proportion of 46,XX karyotypes from products of conception represents maternal cell contamination. When maternal cells rather than fetal cells are karyotyped, no information is gained regarding the chromosome constitution of the abortus, and genetic counseling regarding recurrence risks for future pregnancies may be inaccurate. Thus laboratories should exercise caution when reporting normal female karyotypes on products of conception and should consider using microsatellite analysis to determine whether 46,XX results are truly representative of the fetal karyotype.