EP21.15: Ultrasound findings: from twin pregnancy with complete hydatidiform mole and coexistent fetus to invasive mole and resolution

Twin pregnancy with a complete hydatidiform mole and coexistent fetus (CHMCF) is a rare condition with a prevalence of one in 22,000-100,000 pregnancies. Most cases have been reported as products of assisted reproductive technology. 20% of patients with a CHM develop gestational trophoblastic neoplasia (GTN) and 2% choriocarcinoma. Complications include pre-eclampsia (14.3%), severe vaginal bleeding (70.3%), and hyperthyroidism (23.3%), with a probability of a surviving neonate from 30% to 50%. We present the case of a 37 year-old patient, G3A1P0, with a twin pregnancy product of in vitro fertilization. The patient was admitted for vaginal bleeding and was evaluated with ultrasound that indicated a bichorial biamniotic 11.4 weeks twin pregnancy. The first growing sac contained a normal fetus. The second sac was empty, placenta showing a “snowstorm sign”. Human chorionic beta-gonadotropin (HCBG) of 266,000 mIU/ml with a diagnosis of gestational trophoblastic disease. The patient chose to interrupt the gestation. Pathology revealed a male fetus, the second placenta exhibited characteristics suggestive of a complete mole. Follow-up ultrasound showed signs of an invasive mole, including an enlarged uterus with heterogeneous contours, mixed echogenicity, a 5cm echogenic mass invading the myometrium, and loss of the endometrial and myometrial interface. Further imaging confirmed an uterine lesion and pulmonary nodules. EMA-CO polychemotherapy was initiated, completing 11 cycles. The lesion size decreased, HCBG levels dropped to 1.5 mIU/ml, ultrasound showed an uterus with regular contours, empty cavity, well-defined linear endometrium, and an echogenic residual image. This case provides valuable insight into the ultrasound progression of CHMCF to invasive mole and resolution leaving a residual image due to the myometrial damage, contributing to better understanding of the pathology and its ultrasonographic characteristics.