Calcified foetus, 19th-century illustration. Sagittal section through the abdomen of a pregnant woman with a calcified foetus. Also known as a lithopedion or stone baby, this rare event occurs when a foetus dies and rather than being reabsorbed by the body or aborted, it is instead calcified as part of a defense mechanism intended to protect the body from infection. Artwork from 'Hygiene et Medecine Des Deux Sexes' (1890) by French author Alexis Clerc (1841-1894).