According to a new report of the infant’s case, a baby in Hong Kong was born pregnant with her own siblings.
However, this is not the first case of this type, even though this condition is extremely rare. It is known as fetus in fetu (or foetus in foetu) and it occurs in only about 1 in every 500,000 births. Why exactly it happens is still unknown. One of the theories is that the mass begins as a normal fetus but becomes enveloped inside its twin. The other is that the mass is a highly developed teratoma.
Dr. Draion Burch, a gynecologist and obstetrician in Pittsburgh says that early in the pregnancy weird things can happen and they (doctors) just cannot understand why. His colleague Dr. Drai says: “This is one of those medical mysteries.”
As mentioned above, the World Health Organization considers this tiny fetus found within an infant to be a kind of teratoma, or tumor – not a normally developing fetus.
Nevertheless, the doctors who treated this baby girl born in Hong Kong said that rather than a teratoma, the tiny fetuses were the remains of sibling twins that were absorbed during the pregnancy.
This infant was referred to Dr. Yu Kai-man, a gynecologist and obstetrician at Queen Elizabeth Hospital in Hong Kong. According to the case report, it was suspected to have a tumor at first.
During the prenatal ultrasound an unusual mass within the infant was seen, but, to the doctors, it was unclear what exactly the mass was.
When the baby girl was about 3 weeks old, a surgery was made and the surgeons discovered two fetuses between her liver and her kidney.
The case report said that one of the fetuses weighed 0.5 ounces (14.2 grams) and the other 0.3 ounces (9.3 grams) — corresponding to about 8 and 10 weeks’ gestation. Each of the babies had an umbilical cord that linked to a placenta-like mass in the girl’s belly.
Being too young to have conceived the fetuses herself, the baby girl was obviously one of triplets once, according to the researchers. Then, the two smaller fetuses were absorbed into the body of the remaining child, for some mysterious reason.
It is most likely that the fetuses have still been alive and growing when they were absorbed. However, according to Brunch, after the absorption their development couldn’t proceed normally. In Brunch’s words: “They need placental flow and all that other stuff to really grow”.
Brunch also claims that fetus-in-fetu may be similar to a surprisingly common phenomenon: vanishing twin syndrome. In a lot of twin pregnancies, one of the twins is absorbed and “vanishes” into the body of the other. He adds: “When you do a delivery and you see an extra placenta and a cord, you say, ‘Oh, it must have been a twin,’”
Fetus-in-fetu has been reported in about 200 cases in the medical literature. According to NBC News, in 2006, doctors in Pakistan removed two fetuses from a 2-month-old girl named Nazia. And as the Seattle Post-Intelligencer reported, in 2011, an 18-year-old boy had his retained twin removed in a major surgery.