Hydatidiform mole: cytogenetic marker analysis in twin gestation. Report of two cases.

A hydatidiform mole associated with a fetus proved to be the result of twin gestation. On microscopic examination of the placenta the case was classified as a partial hydatidiform mole. Chromosomal markers were, however, consistent with a normal conception and a mole of diploid androgenetic origin. Chromosome analysis of a morphologic complete molar specimen yielded two cell lines, one consistent with a normal conception and one with diploid androgenesis. Twinning in molar specimens must therefore be considered, regardless of macroscopic appearance. The prenatal diagnosis of a coexisting fetus and molar placenta poses a real clinical problem; analyses must distinguish between a partial mole plus a triploid fetus and a normal fetus occurring with a partial or a complete mole. The distinction is important for decisions made during pregnancy and may be of prognostic significance after termination. The usefulness of chromosome marker analysis in distinguishing between the various origins is pointed out, and it is suggested that twin pregnancy with hydatidiform mole is more frequent than its description in the literature would suggest.