Hydatidiform mole

An uncommon noncancerous tumour that develops from placental tissue early in a pregnancy in which the embryo has failed to develop normally. The mole, which resembles a bunch of grapes, is caused by degeneration of the chorionic villi. The cause of the degeneration is unknown. In a small number of affected pregnancies, the mole develops into a choriocarcinoma. Vaginal bleeding and severe morning sickness generally occur. Ultrasound scanning reveals the tumour. Urine and blood tests detect excessive amounts of human chorionic gonadotrophin (see gonadotrophin, human chorionic), which is produced by the tumour. The tumour can be removed by suction, a D and C, or, less commonly, a hysterectomy.