Lithopedion

A lithopedion – also spelled lithopaedion or lithopædion – (Ancient Greek: λίθος = stone; Ancient Greek: παιδίον = small child, infant), or stone baby, is a rare phenomenon which occurs most commonly when a fetus dies during an abdominal pregnancy, is too large to be reabsorbed by the body, and calcifies on the outside as part of a maternal foreign body reaction, shielding the mother's body from the dead tissue of the fetus and preventing infection.