Well, science calls it a lithopedion, which is Greek for stone baby.
News organizations have been all over the story of these two women in their '80s going to their doctor for stomach pains, only to find something like this in their bellies. The fetuses had turned to stone 40 plus years ago.
How could this possibly happen?
Well, it turns out that the body can be really stupid and really smart at the same time.
The first part is the screw up. It's when a pregnancy that occurs outside of the womb in the abdominal cavity.
The second part is the genius. The mother's body, recognizing that the fetus could be a threat, coats it in calcium, like an oyster turning an irritating grain of sand into a nice smooth pearl.
There have been about 300 cases a stone babies reported in medical literature. And they show up even further back in time. Archaeologists digging at a grave site in Texas found a stone baby that's apparently over 3,000 years old.
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Critical thinking challenge: How does a stone baby form?