Bedwetting, or enuresis, occurs when a child who has developed bladder control during the day continues to wet the bed at night. For very young children, this is normal. Bedwetting is typically not considered a problem until the child reaches a certain age or unless the bedwetting causes significant distress in the child’s life. The age that bedwetting becomes a concern is not entirely agreed upon, but most pediatricians agree that it falls between the ages of 5 and 7 years.

The kidneys produce urine, which is stored in the bladder. The walls of the bladder stretch when it fills and send a message to the brain that it needs to be emptied. Then, the bladder walls contract and the muscle that keeps the bladder closed (sphincter) opens. This pushes the urine through the urethra and out of the body.

In infancy, the kidneys continue to produce urine at all times, both day and night, and the bladder empties whenever it is full. The bladder is small at first and cannot hold much urine, but it increases in capacity every year. As the child grows and develops, several changes take place. A hormone (antidiuretic hormone) is secreted that reduces the amount of urine produced at night. As a child ages, his or her growing bladder can hold more urine. As the central nervous system develops, the child’s brain becomes capable of recognizing a full bladder and keeping it from emptying until the child finds an appropriate time and place to urinate. Eventually, the central nervous system develops to the point that it can wake a sleeping child when the bladder is full.

Children generally gain daytime bladder and bowel control between the ages of 2 and 4 years. They learn to tell their parents or other caregivers when diapers need to be changed and eventually to use the toilet themselves. This is called toilet training. However, daytime bladder control occurs before nighttime control. Children who remain dry during the day may still wet the bed for some time. This may continue for many years, but it becomes less common as the child ages. According to the American Academy of Pediatrics (AAP), about 40 percent of children still wet the bed at age 3. The rate drops dramatically in the fourth year, with about 15 percent continuing to wet the bed, according to the American Academy of Child and Adolescent Psychiatry (AACAP). However, bedwetting typically stops well before puberty.

Nearly all children wet the bed on occasion. Wetting the bed is not typically considered diagnosable enuresis unless it occurs at least twice a week for at least three consecutive months. However, if the bedwetting is less common than this and causes significant distress to the child, a pediatrician may still consider it problematic enuresis.

There are two types of bedwetting:

• Primary enuresis. The most common type of bedwetting. It occurs when the child has never developed consistent nocturnal (nighttime) bladder control and has wet the bed regularly since infancy.
  
  
• Secondary enuresis. Occurs when the child begins to wet the bed after several months or even years of remaining dry at night. It may result from stress or illness.

Although bedwetting can be very embarrassing and stressful for both the child and the parents, it generally causes no physical problems. However, a rash can sometimes develop on the buttocks and genital area. This is particularly true if the child continues to sleep in wet underwear. To prevent a rash, parents can help the child rinse the area each morning. Covering the area with a petroleum ointment before bed may help some children.

In most cases, enuresis is not caused by an illness or physical problem. It is not usually associated with emotional problems. Because girls develop a bit faster than boys, girls tend to develop nocturnal bladder control at an earlier age. According to the American Academy of Family Physicians, more than twice as many boys as girls continue to wet the bed after age 5.