Parental and meiotic origin of triploidy in the embryonic and fetal periods

Triploidy is a common finding both in early spontaneous abortions and in th e fetal period. Previous studies suggested that the majority of triploidy w as the result of diandry, specifically dispermy. Molecular determination of parental origin in fetal triploids has shown that digyny accounts for the majority of triploids in the fetal period. The aim of this study was to det ermine the meiotic level at which the error leading to digynic triploidy oc curs and to extend the molecular analysis of parental origin of triploidy i nto the embryonic period. Maternal age of digynic triploids was compared wi th that of the diandric cases. Using polymorphic pericentromeric markers, w e have shown that the majority of digynic triploidy is the result of errors in the second meiotic division. Digyny accounted for the majority of tripl oids, even in the non-fetal cases. Diandry predominated in a subset of the non-fetal cases in which embryos were not present and in which the placenta l findings of partial hydaridiform mole (PHM) were encountered. Maternal ag e differed between the digynic and diandric groups only for the non-fetal c ases; this was attributed to differences in ascertainment.