A molar pregnancy occurs when a fetus is not able to fully form in the uterus. Instead, the fetal tissue becomes a tumor.
In the US, a molar pregnancy occurs in 1 out of every 2,000 pregnancies. In this condition, fetal cells have an abnormal genetic makeup and form a tumor. This tumor, or "mole," can grow and even spread to other parts of a mother's body. In some cases, the mole may turn into a more dangerous cancer called choriocarcinoma.
In this condition, abnormal fetal tissue inside a woman's uterus forms a tumor. The exact reason this occurs is not known. Common risk factors for this condition include: