Objective: Our purpose was to determine the frequency of confined placental mosaicism in newborns with unexplained intrauterine growth retardation compared with infants with appropriate in utero growth.
Study design: Amnion, chorion, and villi from 12 growth-retarded infants and 24 appropriately grown, matched controls were karyotyped. Fluorescence in situ hybridization with chromosome-specific probes was then used to confirm the karyotypic abnormality at additional uncultured placental sites.
Results: Karyotype analysis revealed placental mosaicism involving either aneuploidy or polyploidy in three of 12 (25%) cases versus two of 24 (8.3%) controls. Fluorescence in situ hybridization confirmed the karyotypic abnormalities in the placentas from growth-retarded infants only.
Conclusion: Confined placental mosaicism was identified three times more frequently from placentas of growth-retarded infants compared with those of newborns with appropriate growth. Molecular studies of the placentas suggested a wider distribution of cells with abnormal karyotypes in cases compared with controls and support a biologic influence of placental mosaicism on fetal growth.