Bed-wetting tends to run in families. For many children, it may be a hereditary condition. If one parent has a history of it, the child has a 44-percent chance. Recent research also indicates that some children may not have enough of anti-diuretic hormone during sleep. The hormone reduces urine production.
Studies also show that some bed-wetters have smaller bladders than other children.
While many other children don't need to go to the bathroom during the night, bed-wetters do. But quite often, a child who wets the bed is a deep sleeper. He sleeps so deeply he does not sense when his bladder is full. Even when their parents try to wake them up, they are unresponsive. Bed-wetting may occur regularly or intermittently.