twoheadedness

Twoheadedness is a lay term for a form of conjoined twinning in which an individual is born with two heads. It is a rare outcome of monozygotic twinning, where the embryo only partially splits or develops two heads that remain attached to a single body. The anatomical configuration varies widely: some two-headed individuals share a body with two necks and two heads, while other arrangements involve varying degrees of shared organs such as the chest, abdomen, or digestive systems. In many cases the two brains are separate, and each head has its own sensory input, but the bodies may be fused to differing extents.

Diagnosis and prognosis depend on anatomy and the extent of organ sharing. Prenatal ultrasound can reveal conjoined twinning during pregnancy, often followed by fetal magnetic resonance imaging or computed tomography to map anatomy for planning care. After birth, a multidisciplinary medical team evaluates the newborn to guide treatment decisions.

Prognosis varies and is heavily influenced by the degree of organ sharing and brain separation. Many conjoined twins are stillborn or die in infancy; survival among those born alive ranges widely. In selected cases, surgical separation may be possible to create two distinct individuals, but such procedures are technically demanding and carry substantial risk and ethical considerations. In configurations where separation is not feasible, long-term medical management and supportive care are required.

Ethical and care considerations focus on informed decision-making, quality of life, and the wellbeing of both the individuals and families. Survivors often require ongoing medical follow-up, rehabilitation, and psychosocial support.