Beckwith–Wiedemann syndrome (; abbreviated BWS) is an overgrowth disorder usually present at birth, characterized by an increased risk of childhood cancer and certain congenital features. A minority (<15%) of cases of BWS are familial, meaning that a close relative may also have BWS, and parents of an affected child may be at increased risk of having other children with BWS. While children with BWS are at increased risk of childhood cancer, most children with BWS do not develop cancer and the vast majority of children who do develop cancer can be treated successfully.