Two different phenotypes of fetuses with chromosomal triploidy: correlation with parental origin of the extra haploid set.

Triploidy is a condition in which there is over-representation of one parental genome. Recent work in experimental mouse embryo-genesis suggests that the parental origin of the extra genome in triploidy may have specific effects on both embryonic/fetal phenotype and placental development due to an "imprinting" effect. We studied 19 human triploid fetuses and discerned 2 distinct fetal phenotypes, as well as the previously described placental phenotypes, which correlate with the parental origin of the extra haploid set. Although these findings suggest that in human triploids the parental origin of the extra haploid set is important in determination of both fetal and placental phenotype it is not clear to what degree placental development and function affect the resultant fetal phenotype.