If your child has been potty trained and is having problems controlling their bowel movements, it could be caused by several different reasons. Sometimes a birth defect can cause fecal incontinence or a disease. In most cases, fecal incontinence in children is caused by constipation. Children who are potty trained will become constipated because they do not want to take the time away from play or TV to go to the bathroom. Maybe they feel embarrassed about going to the toilet in a public place or a place that is unfamiliar. If the child continues to hold in the fecal matter, the stool can become hardened and pile up in the rectum.