Fetus-in-Fetu: Mimicking as Teratoma on Antenatal Ultrasound.

Fetus-in-fetu is a rare and unusual condition. In this condition, a malformed parastitc fetal twin develops inside the body of another fetus, most commonly in the abdominal cavity. We present a case which was thought to be a teratoma on antenatal ultrasound. However, on subsequent postnatal imaging and surgery, it was proved to be fetus-in-fetu.