Question: what are the causes of gestational trophoblastic disease?
Answer: Complete hydatidiform moles. In complete hydatidiform moles, a sperm cell fertilizes an abnormal egg cell that has no nucleus (or chromosomes). ... 
Partial hydatidiform moles. ... 
Invasive moles. ... 
Choriocarcinomas. ... 
Placental-site trophoblastic tumor. ... 
Epithelioid trophoblastic tumors.