Why Children Get Constipated

• They were potty-trained too early.
  
  
• They refuse to have a bowel movement (because of painful ones in the past, embarrassment, stubbornness, or even a dislike of public bathrooms).
  
  
• They are in an unfamiliar place.
  
  
• They are reacting to family stress like a new sibling or their parents' divorce.
  
  
• They can't get to a bathroom when they need to go so they hold it. As the rectum fills with stool, the child may lose the urge to go and become constipated as the stool dries and hardens.

source: http://digestive.niddk.nih.gov/ddiseases/pubs/fecalincontinence/index.htm