A one-month-old baby girl in India underwent surgery on Monday to remove her twin sister’s fetus from her stomach.

Pooja Kumar’s newborn daughter was sent home from the hospital with a swollen abdomen. But, after a month of colds, stomach aches and stiffness, the infant was readmitted to Sir Sundarlal Hospital.

That’s when doctors realized the baby was suffering from a medical condition called “fetus in fetu” and the one-pound-one-ounce fetus of the baby’s twin sister was in her stomach.

“Fetus in fetu” is an abnormality which happens only in one in every 500,000 births.

The one-month-old is doing well after surgery and will be named next month.

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