JAMBI, INDONESIA — A 60-year-old Indonesian woman has made headlines after discovering she’d been carrying a calcified fetus for an incredible 37 years. The result of an ectopic pregnancy, the fetus had died after developing outside the womb before becoming a rock-hard mass. Surgeons at a hospital in Jambi, Sumatra operated for more than two-and-a-half hours to remove it.

An ectopic pregnancy occurs when a fertilized ovum attaches and develops outside the uterus. The fetus almost never survives.

In this case, the starved fetus died and, too large to be reabsorbed, resulted in a lithopedion, also known as a ‘stone baby’.

A lithopedion occurs when the mother’s body treats the the dead fetus as foreign tissue. The immune system calcifies the mass, to prevent infection.

With the calcification process uninterrupted for almost four decades, the fetus had become a dense, stone-like mass.

So-called stone babies are one of the rarest phenomena in medical science. The last recorded case occurred in China In 2013, The host mother had carried 32-week-old calcified fetus for nearly 40 years.

In the past 400 years, only around 300 lithopedion cases have been recorded the world over. The specimen in Jambi will be kept for research.