What are the causes of nighttime incontinence?

Many: For children, bedwetting is common and gradually decreases as the child ages. The cause is usually idiopathic and improves with time. Some children require treatment for bedwetting including bed alarms, medications to decrease urine production in kidneys.

Only nighttime?: There are several reasons for incontinence or leakage. I don't know if you are female, but a common cause is damage to the pelvic muscles during childbirth. You don't say whether this is urinary incontinence or fecal incontinence. If urinary, you should see a urogynecologist or a urologist who specializes in pelvic floor disorder. If fecal, you should see a colon and rectal surgeon.