Even before birth, your baby’s days were divided between periods of sleep and wakefulness. By the eighth month of pregnancy or earlier, her sleep periods consist of the same two distinct phases that we all experience:
1. Rapid eye movement (or REM) sleep, the time during which she does her active dreaming. During these periods her eyes will move beneath her closed lids, almost as if she were watching a dream take place. She also may seem startle, twitch her face, and make jerking motions with her hands and feet. All are normal signs of REM sleep.
2. Non-REM sleep, which consists of four phases: drowsiness, light sleep, deep sleep and very deep sleep. During the progression from drowsiness to deepest sleep, your baby becomes less and less active, and her breathing slows and becomes very quiet, so that in deepest sleep she is virtually motionless. Very little, if any, dreaming occurs during non-REM sleep.
At first your newborn probably will sleep about 6-10hours a day, divided into 3- or 4-hour naps evenly spaced between feedings.
Each of these sleep periods will include relatively equal amounts of REM and non-REM sleep, organized in this order: drowsiness, REM sleep, light sleep, deep sleep and very deep sleep.
After about 2-3 months the order will change, so that as she grows older, she will cycle through all the non-REM phases before entering REM sleep. This pattern will last into and through adulthood. As she grows older, the amount of REM sleep decreases, and her sleep generally will become calmer. By the age of three, children spend one-third or less of total sleep time in REM sleep.