Complete hydatidiform mole with a co-existing normal fetus at mid-trimester in a dichorionic diamniotic gestation.

We report a spontaneously conceived dichorionic diamniotic twin pregnancy in which a complete hydatidiform mole co-existed with a structurally normal fetus. An early ultrasound scan demonstrated a viable fetus with an adjacent cystic area initially interpreted as subchorionic haemorrhage. A definitive diagnosis was established at 21 weeks' gestation when repeat ultrasound scan revealed a separate sac containing diffuse vesicular placental tissue consistent with a complete molar co-twin.Although serum β-human chorionic gonadotropin (β-hCG) was elevated (236,580 mIU/mL), this value falls within the physiological range described in twin pregnancies. The diagnosis was based primarily on ultrasound scan findings rather than biochemical parameters.After multidisciplinary counselling, medical termination was performed, followed by ultrasound-guided suction evacuation. Recovery was uncomplicated, with rapid regression of β-hCG levels.