Parental origin of triploidy in human fetuses: evidence for genomic imprinting

Two distinct phenotypes of triploid fetuses have been previously described and a correlation with parental origin of the triploidy has been suggested. We have studied the parental origin of the extra haploid set of chromosomes in nine triploid fetuses using analysis of DNA polymorphisms at a variety of loci. Maternal origin of the triploidy (digyny) was demonstrated in six fetuses with type II phenotype, paternal origin (diandry) in two cases with type I phenotype, and nonpaternity in one case. The predominance of digynic triploids in our study contrasts with the results reported in previous studies in which, through analysis of cytogenetic polymorphisms, paternal origin was found to account for the majority of triploid conceptuses. This difference may be accounted for by a combination of factors--the different methods of parental assignment used and analysis of a different subset of triploid conceptuses. The correlation between the observed phenotypes and the parental origin of triploidy may represent another example of imprinting in human development.