A partial mole is a type of abnormal pregnancy that occurs when an egg is fertilized by two sperm cells instead of one. This results in an abnormal growth of placental tissue, which can lead to complications. Unlike a complete mole, where there is no normal fetal tissue, a partial mole may contain some fetal development, although it is usually not viable. Women with a partial mole may experience symptoms such as vaginal bleeding, an enlarged uterus, or severe nausea. Diagnosis is typically made through ultrasound and blood tests measuring levels of the hormone human chorionic gonadotropin (hCG). Treatment often involves monitoring and, if necessary, surgical removal of the abnormal tissue.