Pregnant woman (illustration) By: Chan Yuan

A teenager was shocked to learn that his unborn twin grew inside his abdomen for 18 years, doctors in India said.

18-year-old Narendra Kumar of Uttar Pradesh, made the shocking discovery after suffering from severe stomach pains for months.

Kumar was rushed to a hospital after vomiting violently.

During an examination, doctors learned that 5 pounds of bones, hair and teeth, had formed in the abdomen of the young man.

Kumar was diagnosed with a rare condition that develops during pregnancy of twins, in which a fetus enters the other through the umbilical cord and ends up living there as a parasite.

Doctors at the Swaroop Narayan Hospital, told the teen that the parasite had been living and growing in his body since birth.