We report the case of a pregnancy of 16 weeks with anemia and a presumptive diagnosis of partial mole. In secondary care this diagnosis was ruled out through ultrasonography and diffuse cysts were found in the myometrium. Spectral Doppler ultrasound showed no flow, but it could be observed with power angiography. Cesarean section was performed at 38 weeks and hysterectomy 24 hours after because of intra-abdominal hemorrhage. Power angiography, spectral Doppler and serum human chorionic gonadotropin are the most useful diagnostic tools in the differential diagnosis of diffuse cavernous hemangioma of the uterus. Postpartum hemorrhage is a likely complication.