A team of Hong Kong doctors has described an extremely rare medical occurrence: what appeared to be a pair of fetuses inside the body of a newborn girl.
They were both joined to a placenta-like mass by umbilical cords. Each one had four limbs, skin, a ribcage, intestines and primitive brain tissue, according to a study published this month in the Hong Kong Medical Journal.
It was “one of those very rare things that make the world stand still,” said Dr. Nicholas Chao, one of the surgeons who operated on the baby. He said he’d never seen anything like it before during his career in pediatric medicine.
The unusual condition, known as “fetus-in-fetu,” is estimated to happen once in every half-million births but has been reported fewer than 200 times worldwide, according to the study published by Chao and his colleagues.
The baby, weighing about 9 pounds, was born in November 2010 to a woman from mainland China. The little girl recovered well from the operation to remove the mass of tissue, Chao said Tuesday.
But uncertainty remains over how the two unusual entities ended up inside her and whether they can even be classed as fetuses.
“There are controversies over what these things really are,” Chao said, explaining that they might be considered as other fetuses that had been in gestation or as a very mature type of tumor, known as a teratoma.
In the case of teratomas, the cells divide and acquire the maturity of the different tissues.
“Both theories are sound,” Chao said, and there’s “not enough hard scientific data to prove either one because of the limited cases.