A one-year-old who had an enlarged head has undergone surgery to remove the foetus of her identical twin from her skull. Doctors at Huashan Hospital at Fudan University in China said the unborn twin had continued growing for months while inside its sibling in the womb and had developed upper limbs, bones and fingernails. This is due to a medical condition known as foetus-in-foetus.
The foetus had gone undetected for a year after the girl's birth and was only found when the surviving twin's parents took their daughter to the hospital because of her large cranium and motor skills. The girl, who has not been named, was subjected to CT scans which showed her unborn twin pressing against her brain. The foetus had managed to survive for a year inside the skull because it shares a blood supply with its sibling but ultimately was surgically removed.
She also had hydrocephalus, a condition that causes a build-up of fluid in the brain that can cause an enlarged head, extreme fatigue and seizures. Medical staff are unsure whether the surviving child will suffer long-term damage as a result of the strange condition. Dr Zongze Li, a neurologist who treated the girl, said: "The intracranial foetus-in-foetus is proposed to arise from unseparated blastocysts."The conjoined parts develop into the forebrain of the host foetus and envelop the other embryo during neural plate folding."Foetus-in-foetus is an extremely rare phenomenon and has only been recorded 200 times, with 18 of these occurring in the brain. The bizarre syndrome has also been seen in the pelvis, mouth, intestines and scrotum. The unborn twin can survive and continue to grow for months inside its sibling, even growing organs and limbs. The condition occurs when identical twins, who are formed when one egg splits, fail to separate completely in the womb, but doctors don't know why this happens.