A mother recently reported to me that: “When we were first training our 4 year old son, he had a difficult bowel movement on the toilet. He cried and became very upset. That was when our worst problems began. After that, he didn’t want to poop at all. He became constipated and would only poop at night in his pull-up, after he went to sleep.”
Having bowel movements in bed, while falling asleep or while sleeping, is not uncommon for children who are functionally constipated. It usually occurs at the onset of functional constipation when a child is intentionally withholding poop in order to avoid another painful bowel movement. Intentional withholding requires a child to pay close attention for any bodily signals of urgency. However, once the child falls asleep, conscious withholding stops and stool passes.
Compared to other symptoms of functional constipation, nighttime bowel movements are relatively easy to eliminate once a child begins to withhold less (or not at all) during the day. Detailed instructions for decreasing and stopping withholding can be found in The Ins and Outs of Poop.