Molecular analysis of a gestation consisting of a complete hydatidiform mole and normal dizygotic twin.

OBJECTIVE

To identify a twin pregnancy consisting of a complete mole and coexistent fetus by means of molecular cytogenetics and DNA polymorphisms.

STUDY

DESIGN

Seven highly polymorphic DNA markers were used to establish the androgenetic origin of a complete hydatidiform mole that coexisted with a normal 46,XY fetus. Cytogenetic analysis of mole nuclei was performed with centromeric probes, demonstrating a 46,XX constitution.

RESULTS

Molar tissue was diploid with two X chromosomes, possibly due to chromosome doubling after monospermic fertilization of an ovum with inactivated or absent nucleus.

CONCLUSION

Although contamination with maternal tissue may be difficult to avoid, molecular markers provide the possibility of distinguishing between a complete hydatidiform mole and coexisting normal fetus versus a partial mole, with methods that can be performed antenatally. This distinction is important since in the first case up to 24% of fetuses described in the literature have been viable, and the risk of subsequent development of persistent trophoblastic tumor in patients with a complete mole and a coexisting fetus is considerably higher than in patients with a single, complete hydatidiform mole.