Twin pregnancy consisting of 46, XY heterozygous complete mole coexisting with a live fetus.

Complete hydatidiform mole and coexistent fetus (CMCF) is a rare occurrence and is associated with an increased risk of persistent gestational trophoblastic diseases. The aim of this study was to reveal a potential risk factor and to determine optimum management of CMCF cases. Molar tissues are cytogenetically divided into two types, homozygous and heterozygous. The molar tissue of our case showed a 46, XY heterozygous complete mole. Genomic DNA was analyzed by the polymerase chain reaction using sets of unlabelled forward and Cy-5-labelled reverse primers for DNA marker loci. The patient developed persistent trophoblastic disease (PTD) with lung metastasis. Since 1980 there have been 13 reports (including our case) that cytogenetically revealed CMCF and clarified the clinical outcome. Nine of the 16 CMCF cases before 21 weeks of gestation and seven of the 12 CMCF cases after 22 weeks of gestation developed PTD. The incidence of PTD from CMCF was not related to the gestational age at termination or delivery. There were 10 case reports that analyzed the zygosity of a mole, heterozygous or homozygous. Two of six homozygous and three of four heterozygous moles in CMCF cases developed PTD. A heterozygous mole is thought to be a high risk factor for the incidence of PTD. Cytogenetic study is clinically useful for the optimum management of CMCF cases.