A molar pregnancy is a rare complication that occurs during early pregnancy, where abnormal tissue grows inside the uterus instead of a normal embryo. This tissue can form a mass called a mole, which can be either complete or partial. In a complete mole, there is no normal fetal tissue, while a partial mole may contain some normal tissue along with abnormal growth. Symptoms of a molar pregnancy can include unusual vaginal bleeding, rapid growth of the uterus, and severe nausea. Diagnosis is typically made through ultrasound and blood tests measuring human chorionic gonadotropin (hCG) levels. Treatment usually involves removing the abnormal tissue to prevent complications.