The diagnosis of hydatidiform mole is most commonly made by an ultrasound, a test which uses sound waves to show the contents of the uterus. The ultrasound picture of a complete hydatidiform mole will show the uterus filled with cysts. There is no evidence of a fetus.
The early diagnosis of a partial hydatidiform mole will look like a miscarriage or show an abnormal fetus with an abnormal placenta depending upon the number of weeks pregnant. In most cases of partial mole, the diagnosis is made by the pathologist. A blood test will also be done to look for a hormone called human chorionic gonadotropin (known as hCG or beta-hCG) which is also present in normal pregnancy. This hormone is an important test which will be used to determine whether the molar pregnancy will become malignant, to determine if treatment is working, and to find out if the GTD has returned.
The diagnosis of choriocarcinoma is usually made when the patient develops abnormal vaginal bleeding or other symptoms, or on rare occasions when a pregnancy test is found to be elevated and there is no pregnancy.