The origin of human triploidy is controversial. Early cytogenetic studies found the majority of cases to be paternal in origin; however, recent molecular analyses have challenged these findings, suggesting that digynic triploidy is the most common source of triploidy. To resolve this dispute, we examined 91 cases of human triploid spontaneous abortions to (1) determine the mechanism of origin of the additional haploid set, and (2) assess the effect of origin on the phenotype of the conceptus. Our results indicate that the majority of cases were diandric in origin because of dispermy, whereas the maternally-derived cases mainly originated through errors in meiosis II. Furthermore, our results indicate a complex relationship between phenotype and parental origin: paternally-derived cases predominate among "typical" spontaneous abortions, whereas maternally-derived cases are associated with either early embryonic demise or with relatively late demise involving a well-formed fetus. As the cytogenetic studies relied on analyses of the former type of material and the molecular studies on the latter sources, the discrepancies between the data sets are explained by differences in ascertainment. In studies correlating the origin of the extra haploid set with histological phenotype, we observed an association between paternal-but not maternal-triploidy and the development of partial hydatidiform moles. However, only a proportion of paternally derived cases developed a partial molar phenotype, indicating that the mere presence of two paternal genomes is not sufficient for molar development.

In humans, the relationship between advancing maternal age and the incidence of trisomy has been long established, but the possible effect of increasing age of the father remains controversial. Using a fluorescence in situ hybridization (FISH) approach to directly examine individual sperm for aneuploidy of the sex chromosomes and chromosome 18, we have analyzed approximately 400,000 sperm from 24 men aged 18-60 years. There was no obvious relationship between increasing age and disomy 18, but the incidence of XY,YY and XX disomy all were significantly elevated among older men. This suggests that older men, like older women, have an increased likelihood of producing aneuploid offspring by comparison with their younger counterparts.

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