Molar pregnancy and living normal fetus coexisting until term: prenatal biochemical and sonographic diagnosis

The extremely rare condition of molar pregnancy with a coexisting fetus progressing to a viable infant, is reported. At 20 weeks gestational age, prenatal diagnosis was made by biochemical and sonographic findings, in which elevated free beta-human chorionic gonadotrophin (HCG, 500 ng/ml) was noted and ultrasound showed a well-defined multicystic snowstorm-like mass connecting with placenta. Chromosomal evaluation by amniocentesis was normal (46,XY) and ultrasound showed no fetal abnormalities, so the patient decided to keep the pregnancy and had no significant complications noted in the antepartal period. At 38 weeks gestational age, a Caesarean section was performed due to cephalopelvic disproportion and a 3380 g, living boy was delivered. The infant did not show any abnormality. The placenta and the connecting hydatidiform molar tissue were delivered manually. Subsequently, since persistent elevated beta-HCG was noted 2 months later, the patient was treated with chemotherapy for gestational trophoblastic disease. A normal beta-HCG concentration was noted thereafter. Prenatal differential diagnosis and postnatal management are discussed as well as the rationale for allowing the pregnancy to continue after the diagnosis at 20 weeks gestational age.