Finally, structural chromosome alterations such as deletions/duplications (1–2% of BWS cases) and uniparental disomy (UPD) at 11p15.5 involving CDKN1C (10–20% of BWS cases) [15] cause umbilical hernias in about half of patients, whereas in others no abdominal wall defects are described [18]. Here, CDKN1C is linked to Beckwith-Wiedemann syndrome.