Bed wetting is the most common and persistent sleep problem in children. Most children between 18 months and 2 years of age become aware of the sensations of a full bladder during the daytime and begin to communicate that they must go to the bathroom. However, they often do not give much warning. Between 2 and 3 years of age, they are better able to inhibit or hold their urine until they reach the toilet. A child must have mastered these developmental skills before s/he can be trained to remain dry at night time.