What is "lithopedion"

n. (context medical English) A calcium-encased foetus that occurs in ectopic abdominal pregnancies when the foetus dies and is not reabsorbed by the maternal body, whereby the maternal system encases the foreign body (foetus) in calcium to isolate it.

A lithopedion – also spelled lithopaedion or lithopædion – ( = stone; = 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.

Lithopedia may occur from 14 weeks gestation to full term. It is not unusual for a stone baby to remain undiagnosed for decades, and it is often not until a patient is examined for other conditions or a proper examination is conducted that includes an X-ray, that a stone baby is found.

The condition was first described in a treatise by the physician Abulcasis in the 10th century, but fewer than 300 cases have been noted in 400 years of medical literature. The earliest lithopedion is one found in an archaeological excavation at Bering Sinkhole, on the Edwards Plateau in Kerr County, Texas dated to 1100 BC. Another early example was found in a Gallo-Roman archaeological site in Costebelle, southern France, dating to the 4th century.

In 1880, German physician Friedrich Küchenmeister reviewed 47 cases of lithopedia from the medical literature and identified three subgroups: Lithokelyphos ("Stone Sheath"), where calcification occurs on the placental membrane and not the fetus; Lithotecnon ("Stone Son") or "true" lithopedion, where the fetus itself is calcified after entering the abdominal cavity, following the rupture of the placental and ovarian membranes; and Lithokelyphopedion ("Stone Sheath [and] Child"), where both fetus and sac are calcified. Lithopedia can originate both as tubal or ovarian pregnancies.