The diagnosis of a molar pregnancy, or hydatidiform mole is most commonly indicated by an ultrasound, a test which uses sound waves to show the contents of the uterus. If a patient has a complete hydatidiform mole, it is common for the ultrasound picture to show the uterus filled with cysts, with no evidence of a fetus.
The ultrasound findings 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 the patient is pregnant. In all cases of molar pregnancy, the diagnosis is definitively established by pathologic evaluation of the tissue removed at the time of uterine evacuation.
A blood test for a hormone called human chorionic gonadotropin (hCG) will also be performed. This hormone is present in both normal and abnormal pregnancies. In cases of GTD this is often quite elevated. This is an important test which will follow a diagnosis of molar pregnancy and will be used to determine whether the molar pregnancy has become malignant, to determine if treatment is working, and to find out if the GTD has returned.