Important Infant Sleep FactsIn order to better understand the how-to’s of getting you and your baby to enjoy going to sleep and staying asleep, here are some important principles of sleep that every new parent needs to understand.
1. How you sleep.After dressing or undressing for bed, most adults help themselves relax for sleep by performing various bedtime rituals: reading, listening to music, watching TV, or having sex. As you drift into sleep, your higher brain centers begin to rest; enabling you to enter the stage of deep sleep called “non-REM” (non-rapid eye movement — NREM), or deep sleep (also called quiet sleep). Your mind and body are quietest during this stage of sleep. Your body is still, your breathing is shallow and regular, your muscles are loose, and you’re really “zonked.” After about an hour and a half in this quiet sleep stage, your brain begins to “wake up” and start working, which brings you out of your deep sleep and into light sleep or active sleep, called rapid eye movement or “REM” sleep. During this stage of sleep your eyes actually move under your eyelids as your brain exercises. You dream and stir, turn over, and may even adjust the covers without fully awakening. It is during this sleep stage that you may fully awaken to go to the bathroom, then return to bed and fall back into a deep sleep. These alternating cycles of light and deep sleep continue every couple hours throughout the night, so that a typical adult may spend an average of six hours in quiet sleep and two hours in active sleep. Thus, you do not sleep deeply all night, even though you may feel as though you do.
2. How your infant sleeps.You’re rocking, walking, or nursing your baby and her eyelids droop as she begins to nod off in your arms. Her eyes close completely, but her eyelids continue to flutter and her breathing is still irregular. Her hands and limbs are flexed, and she may startle, twitch, and show fleeting smiles, called “sleep grins.” She may even continue a flutter-like sucking. Just as you bend over to deposit your “sleeping” baby in her crib so you can creep quietly away, she awakens and cries. That’s because she wasn’t fully asleep. She was still in the state of light sleep when you put her down. Now try your proven bedtime ritual again, but continue this ritual longer (about twenty more minutes). You will notice that baby’s grimaces and twitches stop; her breathing becomes more regular and shallow, her muscles completely relax. Her fisted hands unfold and her arms and limbs dangle weightlessly. Martha and I call this “limp-limb” sign of deep sleep. Baby is now in a deeper sleep, allowing you to put her down and sneak away, breathing a satisfying sigh of relief that your baby is finally resting comfortably.
NIGHTTIME PARENTING LESSON #1:Babies need to be parented to sleep, not just put to sleep. Some babies can be put down while drowsy yet still awake and drift others need parental help by being rocked or nursed to sleep. The reason is that while adults can usually go directly into the state of deep sleep, infants in the early months enter sleep through an initial period of light sleep. After twenty minutes or more they gradually enter deep sleep, from which they are not so easily aroused. As you probably know from experience, if you try to rush your baby to bed while she is still in the initial light sleep period, she will usually awaken. Many parents tell me: “My baby has to be fully asleep before I can put her down.” In later months, some babies can enter deep sleep more quickly, bypassing the lengthy light sleep stage. Learn to recognize the stages your infant sleeps in. Wait until your baby is in a deep sleep stage before transitioning her from one sleeping place to another, such as from your bed to a crib or from carseat to bed or crib.
3. Babies have shorter sleep cycles than you do.Stand adoringly next to your sleeping baby and watch him sleep. About an hour after he goes to sleep, he begins to squirm, he tosses a bit, his eyelids flutter, his face muscles grimace, he breathes irregularly, and his muscles tighten. He is reentering the phase of light sleep. The time of moving from deep to light sleep is a vulnerable period during which many babies will awaken if any upsetting or uncomfortable stimulus, such as hunger, occurs. If the baby does not awaken, he will drift through this light sleep period over the next ten minutes, and descend back into deep sleep. Adult sleep cycles (going from light to deep sleep, and then back to light sleep) lasts an average of 90 minutes. Infant sleep cycles are shorter, lasting 50 to 60 minutes, so they experience a vulnerable period for nightwaking around every hour or even less. As your baby enters this light sleep, if you lay a comforting hand on your baby’s back, sing a soothing lullaby, or just be there next to baby if he is in your bed; you can help him get through this light sleep period without waking.
NIGHTTIME PARENTING LESSON #2:Some babies need help getting back to sleep. Some “resettlers” or “self-soothers” can go through this vulnerable period without completely awakening, and if they do wake up, they can ease themselves back into a deep sleep. Other babies need a helping hand, voice, or breast to resettle back into deep sleep. From these unique differences in sleep cycle design, we learn that one of the goals of nighttime parenting is to create a sleeping environment that helps baby go through this vulnerable period of nightwaking and reenter deep sleep without waking up.
4. Babies don’t sleep as deeply as you do.Not only do babies take longer to go to sleep and have more frequent vulnerable periods for nightwaking; they have twice as much active, or lighter, sleep as adults. At first glance, this hardly seems fair to parents tired from daylong baby care. Yet, if you consider the developmental principle that infants sleep the way they do — or don’t — for a vital reason, it may be easier for you to understand your baby’s nighttime needs and develop a nighttime parenting style that helps rather than harms the natural infant sleep rhythms. Here’s where I’m at odds with modern sleep trainers who advise a variety of gadgets and techniques designed to help baby sleep more deeply through the night — for a price, and perhaps at a risk.