Detection of a lithopedion coexisting with a 12-week viable intrauterine pregnancy: a rare case report.

Introduction: A lithopedion ('stone baby') is a rare complication of abdominal pregnancy from calcification of a deceased fetus. Coexistence with a viable intrauterine pregnancy is extraordinarily rare. Case presentation: A 27-year-old lady (G2P1L1) with a history of cesarean section presented with acute abdominal pain at 12 weeks of gestation. Ultrasonography revealed a single viable intrauterine fetus and a complex extrauterine mass containing calcified fetal structures with posterior acoustic shadowing suggestive of a dead fetus corresponding to 22 weeks of gestation, consistent with lithopedion. Because of symptoms, possible mass effect on the gravid uterus, and risk of mechanical obstruction as pregnancy progressed, exploratory laparotomy was performed. The lithopedion was excised without disturbing the ongoing pregnancy. Postoperative recovery was uneventful, and follow-up confirmed continued normal intrauterine gestational development. Discussion: A lithopedion coexisting with a viable gestation has been documented in fewer than a dozen modern cases. Prior cesarean section is a recognized risk factor for uterine scar disruption, increasing susceptibility to secondary abdominal pregnancy. Diagnosis is often delayed because vague symptoms may be attributed to the ongoing pregnancy. Although observation may suffice when asymptomatic outside pregnancy, surgery is usually advised when symptoms or mass-effect risks are present. Conclusion: Ultrasonography is critical when evaluating abdominal pain during pregnancy. In symptomatic cases diagnosed during gestation, individualized surgical planning may allow safe removal of a retained lithopedion while preserving the viable intrauterine pregnancy and reducing mass-effect-related obstetric complications.