Clinical features of multiple conception with partial or complete molar pregnancy and coexisting fetuses.

The estimated incidence of twin pregnancy consisting of hydatidiform mole and a coexisting fetus is 1 per 22,000-100,000 pregnancies. Since 1965, nine patients with this entity have been treated at the New England Trophoblastic Disease Center (NETDC), Boston. One patient had a partial hydatidiform mole coexisting with a normal placenta and fetus. The other eight patients had twin pregnancies with a complete hydatidiform mole (CHM) and coexisting fetus. We compared the clinical outcomes in these 8 patients and 14 additional published case reports of multiple gestations composed of CHM and coexisting fetuses with a group of 71 patients with singleton CHM treated at NETDC. Twelve of the 22 patients (55%) with CHM and coexisting fetuses developed persistent gestational trophoblastic tumor, requiring chemotherapy. Five of these patients developed metastases requiring multiple cycles of chemotherapy to achieve remission. The presenting symptoms of multiple conception with CHM and coexisting fetuses were similar to those in patients with a singleton conception and complete mole. However, as compared to singleton CHM, patients having a multiple conception with CHM and coexisting fetuses were diagnosed at a later gestational age, had higher preevacuation beta-human chorionic gonadotropin levels and had a greater propensity to develop persistent tumor. These data indicate that patients with multiple conceptions consisting of CHM and coexisting fetuses are at high risk of developing persistent gestational trophoblastic tumor.