After birth, the rectus abdominus muscles strengthen, closing towards each other in the midline, causing the umbilical ring to close. In most children, this closure is complete by 5 years of age, although it may take longer, sometimes into the preteen years.
If the opening is greater than 1.5cm, if there is a large amount of protruding skin or if there is an underlying disorder (such as Beckwith-Wiedemann, trisomy 21, hypothyroidism or Ehler-Danlos) or raised intraabdominal pressure from ascites, the umbilical ring may not close. Umbilical hernias are more common in children of African descent.
Umbilical hernias very rarely interfere with feeding, unless bowel is contained within it. Incarceration and strangulation is very rare.
Most umbilical hernias will spontaneously resolve and referral to a surgeon is usually not required until a child is 4 years old, unless a complication arises. Even when 4, if it is felt the hernia will eventually spontaneously close, observation may be all that is required.