The BWS presents itself in childhood with variably pronounced phenotype of the above mentioned clinical characteristics.
In particular, macroglossia (present at 85%) and hypoglycemia with a high need for glucose substitution (present at approx. 50%) allow a clinical diagnosis to be made already during the neonatal period. Apart from additional symptoms and complications (premature birth, abdominal wall defects, hyperinsulinism that is difficult to treat), the newborns usually develop in a regular and neurologically inconspicuous manner. A neurocognitive developmental delay may occur after severe neonatal hypoglycemia or chromosomal rearrangement. Macroglossia can cause additional difficulties due to feeding difficulties, airway obstruction and persistent hypersalivation, and about 40% of children have a surgical reduction of the tongue.
Up to the age of 7, children with BWSp have a much higher risk of cancer, depending on the genotype, so that close control examinations (see below) are recommended. Before puberty, the tumor risk is similar to that of the normal population. In adulthood the clinical symptoms are often very discreet or no longer identifiable.