Placental Mosaicism in Multiple Gestation: Complete Hydatidiform Mole with Coexisting Twin Fetus

Hydatidiform mole coexistent with a live fetus (CMCF) is a rare entity occurring in 1:20,000 to 1:100,000 pregnancies. Three mechanisms of this type are possible: (1) a singleton pregnancy consisting of partial mole with a triploid fetus, (2) a twin gestation consisting of an androgenic complete hydatidiform mole with a biparental diploid fetus, and (3) a twin gestation consisting of a biparental diploid fetus with a normal placenta and a partial hydatidiform mole (PHM) with a triploid fetus. The abnormal triploid fetus in a partial mole tends to die in the first trimester while the fetus coexisting with a complete or partial mole in the dizygotic twin pregnancy has a chance to survive. Early detection and diagnosis of a molar gestation with a viable fetus is needed to allow medical interventions, if available. Three cases of complete mole with a twin fetus (CMTF) that were diagnosed in the prenatal period by ultrasonography will be presented. This report will also discuss the indications for continuing the pregnancy, and review the literature on the recommended prenatal care, intrapartum management, and postpartum surveillance. This report aims to encourage others to document cases of CMTF in order to arrive at a consensus regarding its optimal management.