Features of BWS include:
- overgrowth (a high birth weight, and/or children who are bigger than other children)
- hemihypertrophy (one side of the body grows more than the other)
- macroglossia (a large tongue which may cause breathing, feeding or speech difficulties)
- Abdominal wall defects ranging from exomphalos (a hole in the abdomen that allows abdominal organs to poke through the navel see entry Abdominal Wall Defects) to umbilical hernia
- hypoglycaemia (low blood sugar) after birth
- characteristic facial appearance
- visceromegaly (abnormally large abdominal organs)
- kidney abnormalities.
Children with BWS are at an increased risk of developing several types of cancerous and noncancerous tumours, such as a rare form of kidney cancer called Wilms' tumour, rhabdomyosarcoma (a cancer of muscle tissue), and hepatoblastoma (a form of liver cancer). Not all children with BWS are at risk for Wilms' tumour but those that are should be screened regularly for these tumours. For those children who do develop a Wilms' tumour the treatment is generally successful.