Gestación gemelar bicorial biamniótica con un feto vivo y una mola parcial del otro gemelo

Twin pregnancy with one sac containing a live fetus and a second sac containing a partial embryonic mole is an extremely rare entity. A 22-year-old nulliparous woman was admitted to our hospital at 16 weeks' gestation due to persistent hyperemesis unresponsive to the usual medication. Ultrasound examination revealed a bichorial biamniotic twin pregnancy with one live fetus and another fetus with absent fetal heart rate and a biometry of 12-13 weeks. The placenta of the second fetus showed signs of diffuse molar changes. The diagnosis was made with chorionic villus sampling biopsy. The patient wanted to continue with the pregnancy and was followed-up as a high risk pregnancy. Labor was induced at 38 weeks' gestation due to preeclampsia. Outcome was favorable and the patient remains asymptomatic.