Complete hydatidiform mole coexisting live fetus in a twin pregnancy

Introduction: This study describes pathologic characteristics and clinical significance of a rare case of twin pregnancy, consisting of a complete hydatidiform mole and coexistent fetus (CHMF). In addition, a review of the literature was conducted. Case report: A complete hydatidiform mole and a coexisting fetus at 15 weeks gestation are reported. Ultrasound revealed a vital fetus alongside a normal placenta and a separate snow-storm cystic mass with features of a hydatidiform mole. The patient developed severe complications including excessive uterine size, anemia, preeclampsia, hyperthyroidism, and hypoproteinemia. Termination of pregnancy was chosen by the patient and performed thereafter. At 2 years follow up, there was no sign of persistent trophoblastic disease. Both the fetus and molar placenta had a 46, XY karyotype, which is rare in complete hydatidiform mole. Conclusion: Twin pregnancies consisting of a complete hydatidiform mole and coexistent fetus are rare. Individualized treatment of ongoing pregnancy with CHMF is crucial due to an increased risk of developing maternal complications. Close surveillance also in case of pregnancy termination is needed. Our case aimed to raise awareness among physicians of this rare but extremely mortal disease.