Molar pregnancy

A molar pregnancy, also known as a hydatidiform mole, is an abnormal form of pregnancy in which a non-viable fertilized egg implants in the uterus. It belongs to the gestational trophoblastic diseases. The uterus holds a growing mass of swollen chorionic villi that resembles a cluster of grapes, and the products of conception may or may not contain fetal tissue. Molar pregnancies are classed as complete or partial. A complete mole arises when one or two sperm combine with an egg that has lost its DNA, while a partial mole arises when a normal egg is fertilized by one or two sperm, giving a triploid or tetraploid genotype. Complete moles carry a risk of developing into choriocarcinoma, and the condition occurs in roughly 1 in 1,000 pregnancies in the United States, with higher rates in parts of Asia.