Molar pregnancy is an abnormal form of pregnancy, characterize by the presence of a hydatidiform mole (or hydatid mole, mola hytadidosa), an anomalous growth containing a nonviable embryo which implants and proliferates within the uterus. In some cases the uterus contains a normal embryo in addition to the mole. A hydatidiform mole is removed upon diagnosis because there is some risk that it develop into choriocarcinoma, a form of cancer.