Ultrasound appearance of a developing mole.

A 40-year-old primigravida at her 9th week of pregnancy presented with uterine bleeding and an ultrasound picture of a non-embryonic pregnancy with an empty gestational sac but a thickened base of high echogenicity. A week later this thickened area showed a placenta-like disc with a picture of early molar change. At ultrasound follow-up, this progressed to a full hydatidiform mole filling the whole of the uterine cavity; the empty gestational sac had disappeared. The molar pregnancy was confirmed histologically following suction evacuation of the uterus. Early ultrasound diagnosis of a non-embryonic pregnancy or a blighted ovum may not rule out the presence of abnormal trophoblast associated with hydatidiform mole. Failed early pregnancies should be evacuated immediately once diagnosed.