For some women, pregnancy can become an unexpectedly painful experience. However, not every pregnancy proceeds to full term. Ectopic pregnancy is one of the most dangerous pregnancy complications, occurring when a fertilised egg attaches outside the uterus. The uterus is uniquely designed to expand, provide an adequate blood supply, and safely support a developing pregnancy.
In case implantation is done in other places, the pregnancy is unable to proceed normally, and it may be a serious threat to the health of the mother. In very rare cases, implantation occurs in the abdominal cavity rather than in the reproductive organs. This is referred to as an abdominal pregnancy, in which the embryo is attached to the bowel or to the lining of the abdomen. Such pregnancies often go undetected, particularly in areas with limited access to healthcare facilities.
This outcome is exceptional, despite occasional reports of abdominal pregnancies reaching late gestation and, in rare instances, resulting in the birth of a healthy baby. More frequently, however, abdominal pregnancies result in one of the rarest and strangest effects recorded in medicine: the development of a lithopaedion. The term lithopaedion originates from Greek and means “stone baby.” It is extremely rare, with only a limited number of cases reported in the medical literature.
In such scenarios, women may experience early pregnancy symptoms and, in some cases, appear to go into labour. Others even go through labour, whereby the body initiates childbirth, despite no baby being delivered. In other cases, the pregnancy might pass completely unnoticed. Unfortunately, the unborn baby in such situations does not survive. Once the gestation period is about three months, the fetal skeleton starts ossifying, which is a normal biological process in which cartilage gets hardened into bone. After ossification, the remains are already too big and complex in structure to be absorbed by the body.
The placenta in a normal pregnancy controls the blood flow of nutrients and the immune system between the mother and the foetus. Meanwhile, maternal immunity shifts to immune tolerance to prevent rejection of the foetus as foreign. These protective mechanisms are terminated when the foetus becomes non-viable. The fetal tissue is then considered foreign to the immune system.
The body may react to this by calcifying the foetus to shield it against infection or inflammation. Gradual deposition of calcium salts around the tissue, sealing it off from the surrounding organs, is known as calcification and holds the tissue in place. This resistance mechanism is protective, preventing further damage. Pregnancy is not the only time it calcifies. When calcium is deposited in dead or damaged tissue in other parts of the body, it is termed as a process referred to as dystrophic calcification. Calcium interacts with the phospholipids of cell membranes, stabilising the affected region. Coincidentally, there is a similar mechanism that helps in calcium accumulation in blood vessels during atherosclerosis.
It has also been noted that lithopaedion formation occurs in animals such as rabbits, dogs, cats, and monkeys. Among the earliest recorded human cases is that of a 68-year-old French woman who used a lithopaedion since 1582. Another case that has been commonly reported in China involves a woman who carried one for a period of more than 60 years. There have been cases in which some lithopaedions have weighed over two kilograms, and, in a rare case, twin lithopaedions have been found. Some women bear a lithopaedion without showing signs and symptoms, and those with complications such as pelvic abscess, intestinal obstruction, fistula formation, pain, or abdominal swelling. Asymptomatic cases are usually identified at autopsy.
In symptomatic cases, surgical removal is usually necessary, either laparoscopically or open abdominal surgery (depending on the complexity). Diagnosis is typically based on imaging modalities such as X-rays, ultrasound, or CT, with CT providing more detailed images. Though cases of lithopaedion are now extremely rare thanks to contemporary pregnancy testing and prenatal care, it still serves as a very striking example of the fragility of the human body as well as its strength.
References: Taylor A. Stone baby: the rare condition that produces a calcified foetus. The Conversation. January 27, 2026. Accessed January 29, 2026. Stone baby: the rare condition that produces a calcified foetus. The Conversation.
