Weird: How Does a Baby's 'Twin' End Up Inside His Abdomen?

A newborn baby gazes at something
A stock photo of a newborn baby.
(Image credit: Phattana Stock/Shutterstock)

A baby boy in India was born with his own "twin" inside his abdomen — an extremely rare condition called "fetus in fetu." But what causes this to happen?

Doctors first noticed something was wrong when they spotted a mass inside the fetus during a routine ultrasound of the pregnant mother, according to Metro, a news outlet based in the United Kingdom. After the baby was born, doctors performed another scan, and found a partial fetus behind the baby's stomach. The partial fetus had arms, legs and a brain, but no skull, Metro reported.

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Rachael Rettner
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.