Conjoined twins are an exceptionally rare and severe complication of monochorionic twin pregnancy, associated with substantial perinatal morbidity and mortality, as well as complex ethical and surgical challenges. Their embryological origin remains incompletely understood, with partial fission and secondary fusion as the principal proposed mechanisms. Advances in prenatal imaging have improved early diagnosis and characterization, but management remains highly individualized. We conducted a narrative review of literature identified through PubMed/MEDLINE, Scopus, and Google Scholar (search date: August 15, 2026), supplemented by manual screening of reference lists. Priority was given to original studies, systematic reviews, guidelines, and relevant case reports, with a focus on ethical decision-making frameworks.
Prenatal diagnosis is primarily achieved by first-trimester ultrasound, with fetal magnetic resonance imaging and fetal echocardiography providing complementary assessment of shared organs and vascular anatomy. Prognosis depends on the site and extent of fusion, shared organs, and associated anomalies, particularly cardiovascular abnormalities. Elective separation achieves survival rates of up to 50% for at least one twin in selected cases, while emergency separation carries a ~30% mortality rate per twin pair. Management requires multidisciplinary planning and may include termination, expectant management with planned delivery, or postnatal separation.
Ethical dilemmas, such as termination decisions, surgical timing, and informed consent, are analyzed within a proposed framework that considers fetal viability, parental autonomy, resource allocation, and long-term quality of life. Conjoined twins pose a major diagnostic, therapeutic, and ethical challenge. Early accurate imaging, individualized multidisciplinary management, and further research into embryogenesis and ethical frameworks are essential to optimize outcomes and support affected families.