Twin pregnancy associating a complete mole and a normal pregnancy with its own healthy trophoblast is a rare entity. The majority of studies show that the prognosis of such an association includes a risk of progression to a gestational trophoblastic tumor. We report a case of a patient who consulted for second trimester metrorrhagia and whose ultrasound revealed a bi-chorionic twin pregnancy: two gestational sacs, one with a living fetus of 21WA, another containing an amniotic cavity with a trophoblast in honeycomb appearance measuring 14cm. Medical termination of pregnancy was indicated: Induction of labor with misoprostol followed by endo-uterine aspiration. The expulsion product was in the form of a living fetus of 20 weeks with its own trophoblast associated with a vesicular mass of 14 cm and which on histological examination corresponded to a complete hydatidiform mole.

Keywords : Twin Pregnancy; Hydatidiform Mole; Obstetrical Ultrasound.