Fetus in fetu, a medical condition in which a baby is born with its malformed parasitic twin inside its own body, is so rare that it’s been documented less than 200 times in the scientific literature. Now, doctors have reported an even more unusual example of this uncommon developmental abnormality: a baby born with two fetuses inside her abdomen.
As described in the Hong Kong Medical Journal, the Chinese baby girl was born in Queen Elizabeth Hospital back in November 2010. On the day of her birth, she was admitted to the hospital’s neonatal unit because her mother’s 37 week ultrasound revealed an abnormal mass in the baby’s abdomen, which was suspected to be a tumor or perhaps a hemorrhage.
A few days later, the baby was given further ultrasound examinations and a CT scan, which revealed two solid masses, each possessing two long bones and a spine. The decision was therefore made to surgically remove the masses when the baby was just 14 days old.
Examination of the excised masses revealed two fetuses, each possessing an umbilical cord joined to a placenta-like structure. The tiny fetuses were believed to be around 10 weeks of age, measuring 37 mm and 35 mm in length and weighing just 14.2 g and 9.3 g. Despite being different sizes, the level of development was identical. They both possessed four limbs, segmented spines, well-developed rib cages, primitive brain tissue, intestines and an anus.
According to obstetrics and gynecology specialist Dr. Yu Kai-man, this is thought to be the first case of fetus in fetu in the city, and only the second regional case documented. He explained to South China Morning Post that the fetuses were so small that it would have been virtually impossible to detect the condition during prenatal checks.
“Since it is impossible for the little girl to have conceived the pregnancy on her own, the fertilization of the twin fetuses, of course, belongs to her parents, which has gone to the wrong place,” he said.
The baby girl recovered well from the operation, but the causes behind her condition remain unknown. There is still some debate over the origins of fetus in fetu, and the World Health Organization actually classifies it as a highly organized teratoma, which is a type of cancer that contains one or more of the three layers of cells (germ layers) found in a developing embryo. Others believe that it is a twin that starts off developing normally and then becomes enveloped inside its sibling. Although most cases have been found in the abdomen, other reported locations include the scrotum and inside the skull.