A one-year-old girl with an enlarged head underwent surgery to remove her identical twin’s foetus from her skull.
Doctors at Huashan Hospital at Fudan University in China said the unborn twin had developed upper limbs, bones, and fingernails while inside its sibling in the womb for months. This is caused by a condition known as foetus-in-fetus.
The foetus had gone undetected for a year after the girl’s birth and was only discovered when the parents of the surviving twin took their daughter to the hospital due to her large cranium and motor skills.
The unnamed girl underwent CT scans, which revealed that her unborn twin was pressing against her brain.
Because it shares a blood supply with its sibling, the foetus survived inside the skull for a year before being surgically removed.
She also had hydrocephalus, a condition in which fluid accumulates in the brain, causing an enlarged head, extreme fatigue, and seizures.
Medical personnel are unsure whether the surviving child will suffer long-term consequences as a result of the unusual condition.
“The intracranial foetus-in-foetu is proposed to arise from unseparated blastocysts,” said Dr Zongze Li, a neurologist who treated the girl.
“During neural plate folding, the conjoined parts develop into the forebrain of the host foetus and envelop the other embryo.”
Foetus-in-foetus is an extremely rare phenomenon that has only been documented 200 times, with 18 of these occurrences occurring in the brain.
The unusual syndrome has been observed in the pelvis, mouth, intestines, and scrotum.
The unborn twin can survive and grow inside its sibling for months, even growing organs and limbs.
The condition occurs when identical twins, formed when one egg splits, fail to separate completely in the womb, for unknown reasons.