Hydatidiform moles occur in about 1 pregnancy out of 1,000 in the United States and Europe. In very rare cases (less than 1%), a normal fetus can develop along with the hydatidiform mole.

In about 15% of cases, a hydatidiform mole will progress to become an "invasive" mole. Overall, invasive moles occur at an estimated rate of 1 pregnancy in 15,000.

Choriocarcinoma, a malignant form of GTD, is even less common, affecting approximately 1 pregnancy out of 40,000 in the United States. Like other forms of GTD, choriocarcinoma is more common in many Asian and African countries.

About 2% to 4% of hydatidiform moles progress to become choriocarcinoma. But only half of all gestational choriocarcinomas start off as molar pregnancies. About one-quarter of all choriocarcinomas develop in women who have a miscarriage (spontaneous abortion), intentional abortion, or tubal pregnancy (the fetus develops in the fallopian tube, rather than in the uterus). Another one-quarter occur after normal pregnancy and delivery.

Overall, gestational trophoblastic tumors account for less than 1% of female reproductive system cancers.

Cure rates depend on the type of GTD and its stage, as described in the section "How is gestational trophoblastic disease treated?"

Last Medical Review: 10/13/2009
Last Revised: 10/13/2009