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Development of Sleep
(Excerpted from The Dream Sleeper. Printed with permission from Jossey-Bass.)
A child’s sleep patterns and sleeping abilities change tremendously in the first year of life, although what’s “normal” at this age can vary. Some babies sleep through the night, while others sleep in shorter bursts around the clock. Even the same baby can have very different nights back-to-back for no apparent reason.
Birth to Two Months
We are the only species of animal born without a fully formed brain. When we are born, our brains have not yet begun to use their cerebral cortex, where memory and attention reside. Newborns use only their brain stems and therefore are able to do only very basic things like sleep and eat; even their body movements are primarily driven by reflexes. That’s the reason it seems as if your child sleeps the first month away. It’s essentially all she can do. Her mind needs to sleep to keep growing, so it will be ready to help her body start doing cool tricks when she’s physically more mature.
Even the way newborns sleep is underdeveloped. During the first one to two months of life, babies are incapable of deep sleep. They cycle between light sleep and REM sleep until around either weeks of age, when deeper sleep starts to appear. Most newborns do not have trouble falling asleep. That’s the upside. The downside is that because they are always in lighter stages of sleep, they do not generally stay asleep for very long stretches.
Newborns can’t tell the difference between night and day because they do not yet have a circadian rhythm. This is the twenty-four hour biological cycle that tells us daytime is for activity and night is for sleep. This means you’ll be up a lot because their sleep is more equally distributed between day and night. Around six weeks, babies begin to produce the hormone melatonin, a natural neurotransmitter that helps establish a normal sleep-wake cycle. Melatonin, produced by the pineal gland in the brain, helps set the body’s circadian rhythm.
That’s a lot of change in two months. Since all babies develop in slightly different ways and at different rates, we urge you to resist the temptation to compare your baby to others of the same age. There’s a wide rage of what’s normal.
Two to Four Months
At the two-month mark, something major has happened: your baby’s brain stem has started communicating with his cerebral cortex, a process called myelination. This developmental milestone allows your baby to start forming memories so he can start to recall past events (for example, “I made this sound, and my mommy picked me up”).
By three months of age, more regular sleep rhythms start kicking in. Babies are now capable of all four stages of quiet sleep, including the deepest stages.
At this point, some children begin sleeping longer stretches, while babies who previously were perfectly sound sleepers may all of a sudden become incredibly restless. One of the reasons this occurs is that some children think they should let you know whenever they are awake. They now remember how you responded the last time and will call for you to repeat the action. Although it’s true that a baby’s sleep ability at three months is a good predictor of the kind of sleeper he is predisposed to being, it doesn’t mean that he can’t learn to be a sound sleeper. Rather, you might have to be more organized or structured about how you teach your child to sleep and how you keep him on track.
Babies of this age are better able to self-regulate and do some amount of self-soothing because they are now functioning with more of their cerebral cortex instead of only their brain stem. But remember that just because a child doesn’t pick up on self-soothing skills on his own doesn’t mean he can’t be great at it with a little practice and encouragement.
Children start to be on a more predictable schedule at this age. Although they may not be the same day to day, generally most children need to sleep after every one and a half to two hours of being awake.