(Newser) – Being born pregnant is so rare it has only been documented 200 times, but it does happen. Now researchers are reporting this week in the Hong Kong Medical Journal on the November 2010 case of a newborn girl thought to have two tumors in her abdomen that were found to be 8- to 10-week-old fetuses instead. Weighing half an ounce and a third of an ounce, they were far enough along to each have four limbs, a spine, a rib cage, intestines, and an anus, and to be connected through an umbilical cord to a single placenta-like mass. "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," a local doctor tells the South China Morning Post.

The baby girl carrying the fetuses underwent successful surgery to remove them at just two weeks of age. The condition, called fetus in fetu, is thought to occur in 1 in 500,000 births worldwide. This was the second such case to be reported in the region. The World Health Organization has classified it as a type of cancer called mature teratoma, but researchers write "the theory of demised multiple pregnancy has gained much support recently. More evidence is needed to confirm either theory." (Last year, doctors found a 44-year-old calcified fetus in an 84-year-old woman.)

