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.