Tetraploidy in human placenta. A dilemma in molar and non-molar pregnancies

17 cases of partial molar pregnancy were analysed cytogenetically by the direct-preparation method. Eight partial moles were triploid, 7 diploid/tetraploid mosaic, and 2 tetraploid. In the course of prenatal cytogenetic screening, out of 1,263 chorionic villus samplings, 2 tetraploid and 1 diploid/tetraploid cases were found. These cases of partial moles do not fit into the usual patterns of triploid partial moles. The findings presented here suggest that different causative factors may be involved in the origin of molar degenerations. These results also call to attention that tetraploidy is an existent and relatively common abnormality.