A newborn baby's head contained the foetus of its identical twin, leaving doctors shocked

TW: Graphic description

You hear all sorts of crazy stories about giving birth. There's the baby who was born holding his mum's IUD in his hand, and then there's the woman who gave birth to twin girls in two different years.

In this story, the parents got concerned about their daughter’s abnormally large head and motor skills, so they rushed her to the hospital for checks. The doctors couldn’t believe their eyes when they found the foetus of her unborn twin baby in her brain.

An very rare situation

Doctors at Huashan Hospital at Fudan University in China discovered a rare case of Fetus-in-fetu after they attended to a patient - a little girl.

Her parents were concerned about her large head and motor skills so the child underwent CT scans. The hospital staff could believe their eyes when they saw shocking images of the unborn twin pressing against the little girl’s brain.

The foetus of her sibling had continued growing for months while inside her head in the womb and had developed upper limbs, bones and fingernails. When found, it was still alive and had survived so long because it was sharing its sibling's blood supply.

The little one who was just one year old had also developed hydrocephalus, which leads to a build-up of fluid in the brain. It can cause an enlarged head, extreme fatigue and seizures. So, the foetus had to be surgically removed.

Medical staff are unsure whether the surviving child will suffer long-term damage as a result of the rare condition.

Dr Zongze Li, a neurologist who treated the girl, said:

The intracranial foetus-in-foetu 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.

Fetus-in-fetu: an explanation

Fetus-in-fetu is incredibly rare, with only 200 similar cases ever recorded, 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 the medical community don't know why this happens.

Some scientists reckon the healthy twin connects to the mother through the placenta but the other doesn't, instead getting its blood supply via its sibling's blood vessels. As the healthy twin grows, the smaller one is then absorbed.

Another possible cause of Fetus-in-fetu is late cell division, but experts remain divided on the topic.

Read more:

⋙ This baby had severe mobility issues, doctors couldn't believe what they found inside her brain

⋙ This couple made an unusual decision after using a surrogate mother to have a baby

⋙ Rare photo of Boris Johnson’s baby shows just how similar father and son are

Sources used:

- Mirror: 'Baby born with abnormally large head as doctors find unborn twin inside her SKULL'