(ABC NEWS) An elderly Colombian woman was stunned when she went to the doctor for pelvic pain and was told the pain was caused by a 40-year-old “stone” fetus.

The 82-year-old had been carrying the calcified four-pound fetus called a lithopedion for decades without realizing it, according to the Telegraph.

Doctors only discovered the rare medical phenomenon after ordering an X-ray that revealed the lithopedion, also called a “stone baby.” The woman is now expected to undergo surgery to remove it.

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