A 40-year-old foetus was discovered inside the abdomen of an 82-year-old woman. The elderly Colombian woman complained of pain and discomfort in her abdomen, but she never expected she was carrying a foetus. Doctors estimate the foetus remained inside her abdomen for nearly 40 years.Doctors at Tunjuelito Hospital originally diagnosed the woman with gastroenteritis, which can cause diarrhea and cramping. However, an ultrasound ruled out an infection. They eventually ordered an X-ray of her abdomen. When they viewed the results, they were stunned — the elderly woman was carrying a calcified foetus.Although calcified foetus’ are rare, they can happen. The foetus is called a lithopedion, also referred to as a stone baby.A lithopedion begins when a fertilized egg implants and begins to develop outside the uterus. When the egg implants inside the fallopian tube, it is called an ectopic pregnancy.Rarely, a fertilized egg will travel into the abdominal cavity, where it can become implanted anywhere from the bowel to the aorta. Although the foetus cannot survive inside the abdomen, doctors usually terminate the pregnancy to prevent future problems.As reported by NBC News, in most cases the tissue will simply break down inside a woman’s body. However, in the case of the 40-year-old foetus, it continued to grow to an advanced stage.If the foetus continues to develop, it can become too large to absorb. As a natural reaction, the foetus and the surrounding tissue eventually calcify.Lithopedion rarely cause further issues, as they often go unnoticed. For some woman, the foetus is large enough to cause pain and swelling.The Journal of the Royal Society of Medicine cites 280 recorded cases of lithopedion since 1582. While most “stone pregnancies” last around 22 years, at least one woman carried a calcified foetus for more than 60 years.