A lithopaedion or stone baby, is a rare phenomenon which occurs most commonly when a fetus dies during an ectopic pregnancy.
The estimated incidence is at ~ 1.5 to 1.8% of abdominal ectopic pregnancies 4.
If the dead fetus is too large to be re-absorbed by the mother’s body it becomes a foreign body to the mother’s immune system. To protect itself from possible infection, the mother’s body will encase the fetus in a calciferous substance. The fetus is gradually mummified becoming a stone baby. Lithopedions may occur from 14 weeks’ gestation to full term. It is not unusual for a stone baby to remain undiagnosed for decades and found incidentally when taking plain films for various reasons.
Derives from the ancient Greek root litho (λίθο) = stone and the word paedion (παιδίον) = child.