A baby girl in Hong Kong was born "pregnant" with two fetuses in 2010 in a case so rare it's only been documented 200 times ever.
Researchers published the case study on the child born to parents from
mainland China this week in the Hong Kong Medical Journal. The condition, called "fetus-in-fetu," only occurs in about 1 in 500,000 births in the world and is considered a type of cancer called
mature teratoma, the South China Morning Post reported.
The girl was just three weeks old when doctors performed surgery to remove the twin fetuses — ranging from eight to 10 weeks old — from her abdomen, according to the Morning Post. Each "fetus" reportedly contained four limbs, a spine, rib cage, intestines, and an anus.
"It was almost impossible to detect during the prenatal check-up, as the embryo inside the baby was too small," Dr. Yu Kai-man, a specialist in obstetrics and gynecology and a former professor at Chinese University of Hong Kong, told the Morning Post.
"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."
Researchers noted in the study that it is still unknown why or how exactly the condition occurs.
"Less than 200 cases of twin fetus-in-fetu have been reported worldwide, and, to date, this was only the second regional case report," read the conclusion of the study in the Hong Kong Medical Journal.
"Although classified by (World Health Organization) as a variant of mature teratoma, the theory of demised multiple pregnancy has gained much support recently. More evidence is needed to confirm either theory. The widespread use of antenatal ultrasound in early gestation may provide more concrete evidence from longitudinal observation and give light to the aetiology of this intriguing condition."
The theory of mature teratoma, or demised multiple pregnancy, came up last year when doctors discovered a 44-year-old calcified fetus inside the body of an
84-year-old Brazilian woman, according to the Daily Mail.
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