A study published in China revealed an extremely unusual case of an unborn fetus removed from the head of its living twin, IFLScience reported.
The one-year-old girl from Shanghai displayed several indicative problems, such as an enlarged head and motor skill deficiencies. CT scans revealed that her brain was compressed, and there was an excess of fluid caused by a growth in the ventricles, which was discovered to be the child’s unborn twin. The fetus-in-fetu had formed upper limbs and appendages resembling fingers, although the rest of its form was severely underdeveloped.
While this phenomenon may sound bizarre to most, it is known as “fetus-in-fetu” and is extremely rare. It occurs during the early stages of twin pregnancy when the blastocyst, a cluster of dividing cells, fails to separate properly, resulting in one of the embryos being enveloped by the other.
The enveloped embryo fails to develop but remains “alive” due to the other twin’s blood supply. The conjoined parts of the embryos develop into the forebrain of the host fetus and envelop the other embryo during neural plate folding.
Although it is unclear how the girl recovered after the surgery, similar cases have shown that children with fetus-in-fetu can and do recover well.
In a study published in 1982, a six-week-old child with an enlarging head size was found to have a 14-centimetre fetus with developing limbs, a head, and a body inside their body. The fetus was successfully removed, and the child had an “excellent recovery.”
Fetus-in-fetu cases are exceptionally rare, occurring in approximately one in every 500,000 births. They are mostly found within the bodies of the live babies, making them exceptionally uncommon to affect the brain.