A molar pregnancy is a mass of abnormal placental cell growth (hydatidiform mole) inside the uterus that triggers symptoms of pregnancy. A complete molar pregnancy is a tissue mass that can fill the uterus, while a partial molar pregnancy may include severely abnormal fetal tissue.

Symptoms of pregnancy are often intensified in a molar pregnancy. Morning sickness may be severe, the uterus may grow at a faster-than-normal rate, and blood pressure may be unusually high.

The cause of molar pregnancy is thought to be a genetic abnormality. Girls younger than 15 and women older than 40 are at highest risk. Women who have had a molar pregnancy in the past have a slightly increased risk of having another.

All molar growth must be removed from the uterus to prevent cancerous cell growth. After the tissue is suctioned out through the cervix and vagina (vacuum aspiration), the uterus is scraped of any remaining abnormal cells (curettage). Chemotherapy is used when abnormal tissue is or may become cancerous (trophoblastic cancer).