Baby Born Pregnant with Her Own Twins

A baby born in Hong Kong appears to be pregnant with her own siblings, in a very rare case

The baby's condition, known as fetus-in-fetu, is incredibly rare, occurring in only about 1 in every 500,000 births. It's not clear exactly why it happens.

Dr. Draion Burch, an obstetrician and gynaecologist in Pittsburgh said “This is one of those medical mysteries. Weird things happen early, early in the pregnancy that we just don't understand,"

The World Health Organisation considers a tiny fetus found within an infant to be a kind of teratoma, or tumor, rather than a normally developing fetus.

But the doctors who treated the baby girl wrote that rather than a teratoma, the tiny fetuses may instead be the remains of sibling twins that were absorbed during the pregnancy.

The newborn baby was referred to Dr. Yu Kai-man, an obstetrician and gynecologist at Queen Elizabeth Hospital in Hong Kong, because the baby was suspected to have a tumor, according to the case report.

The mother's prenatal ultrasound had revealed an unusual mass within the infant, but it was unclear to the doctors exactly what the mass was.

During surgery, which was done when the girl was about 3 weeks old, the surgeons discovered two fetuses between her liver and her kidney.

One fetus weighed 0.3 ounces (9.3 grams) and the other 0.5 ounces (14.2 grams) — corresponding to about 8 and 10 weeks' gestation, the case report said.

Each of the babies had an umbilical cord that linked to a placenta-like mass in the girl's belly.

The baby girl was obviously too young to have conceived the fetuses herself. Instead, it's likely that the girl was once one of triplets, the researchers said. Then, for some mysterious reason, the two smaller fetuses were absorbed into the body of the remaining child.

The fetuses would likely have still been alive and growing when they were absorbed into the surviving baby's body.