The Science of Infant Sleep Part IV: Falling Asleep versus Staying Asleep

As we wrap up this multi-part series on infant sleep, we return to some of the original questions that led us to focus on this all important area. Several of you asked us about the popular recommendation to make sure that your baby is still partially awake when you put him in his crib. Others wanted to know why babies sleep through the night once or for several weeks and then start waking again. In this post, we'll revisit the interrelationships that we talked about in the last post, but this time, we'll discuss specifically how they may affect your baby's abilities to fall asleep and then stay asleep.

Baby Sleep is Complicated

I'm a big baseball fan (now stay with me, there is a point). One of the things I really love about baseball is that with every new batter, new pitcher, and new situation, the game changes. Baby sleep is a lot like that. Babies' sleep location, their own physical and developmental characteristics, and their parents' behaviors, all interact to influence infants' sleep. And, the game keeps changing as babies grow, as parents change, and when babies sleep in different places. I wish I could give you the answer to get babies to sleep quickly and for long stretches but I continue to believe that there is no single intervention that will help all babies, or even the same baby over time, in all circumstances. Now, I don't mean to imply that there is nothing parents can do. Instead, parents should think of themselves more like the baseball batter adjusting to the pitches that are thrown to them. Some adjustments in parents' actions and in babies' environments will help babies fall asleep, others might help babies stay asleep.

Falling Asleep

Believe it or not, there is a technical term for the time it takes to fall asleep, it's called "sleep-onset latency." Most newborns fall asleep while feeding (but they wake and feed frequently!) so falling asleep becomes more of a problem for older infants, especially those who hate being drowsy. Caffeine exposure and over stimulation can be important factors that might hinder babies' ability to fall asleep. Babies who are sick or uncomfortable (as with teething) will also have problems falling asleep. Dealing with these issues (with help as needed from the doctor) can be a big help to tired parents. But, there are other babies who don't want to fall asleep even when they are not sick or overstimulated. The research we found indicates that consistent bedtime routines (lasting from 20 to 40 minutes) can help babies to wind down. Some routines include a bath, a massage, some rocking, and a story or a song. The key is for parents to be consistent with a series of pleasant and soothing activities night after night. One large study found that a routine helped babies fall asleep faster and stay asleep longer with or without putting the babies down slightly awake.

Staying Asleep

Let's get back to the "put your baby down while awake" recommendation. This suggestion is used primarily as a way to prevent babies from calling out for their caregivers if they wake at night. The idea is that babies who always fall asleep in their parents' arms won't be able to fall asleep any other way. We found several "observational" studies that found that babies who were put down awake were more likely to stay asleep. In observational studies, researchers look at things the way they are and they don't try to change anything as they do in "intervention" studies. Because the same babies who accept being put down awake may sleep longer naturally than those who fight sleep, the relationship between the slightly awake baby and longer sleep may be related more to the baby's characteristics rather than the action of putting the baby down awake. So, we need intervention studies to see if the action results in longer sleep for all babies. This is where it gets tricky. There are plenty of intervention studies that include putting babies down while they are awake but none that includes only this one action (for infants). Most of the interventions include 1) education for parents about infant sleep, 2) standardized bedtime routines, 3) putting baby down at the end of the routine awake or not, and 4) changing parents' response if the baby protests going to sleep. Some of the interventions included instructions for parents to wait to respond (letting the baby cry). In other studies, parents were told to respond by touching the baby (like putting a hand on the baby's back) but not picking the baby up. Some interventions also included white noise, music, and other changes to the sleep environment.

Ok, that's a lot to take in. What does this all mean to you, a tired parent? We'd like to end this series with a few key messages.

• Newborns need to wake for many reasons. Get some help for this tough time.
• A single intervention is not likely to increase sleep for all babies or permanently for any baby.
• When trying to help your baby go to sleep faster and sleep longer, you need to consider his health, age, size and developmental characteristics, your own actions and beliefs, and characteristics of his sleep environment. How a baby sleeps is not an indicator of parenting skill.
• There are a lot of options for parents of older babies to get more sleep. Understanding more about how babies sleep, why they wake, and how "the game changes" over time can help you make informed decisions about what steps will work best for you.

Next time: Back to your questions!

The Science of Infant Sleep Part II: Big Changes in Sleep Patterns (6 to 16 weeks)

The first 6 weeks are finally over! New parents, give yourselves a big "high five!" You are probably noticing that things already seem a little easier. At least, you are more familiar with your babies’ needs and cues and likely to be getting a little more sleep than you were at first. In this post, we’ll share information about some of the changes your baby will go through from 6 to 16 weeks and how these changes might affect how your baby sleeps.

Six to Twelve Weeks

While you’ve been waking up several times at night to feed, diaper, and console your baby, his little body has been going through a lot of development. His body and his tummy have grown and expanded, allowing him to take in more at each feed. He still falls asleep dreaming (remember to look for those eye movements and body twitches), but he spends less and less time in the “active sleep” state after he falls asleep. That means that you won’t have to wait so long to put him down if he is sensitive to position changes when he is dreaming. Just a few minutes should do it! His body also has started to make and use hormones like melatonin and cortisol to help him develop and follow his own circadian rhythms. When he is sleeping, you’ll notice that your baby won't move as much or make as many little noises as he did when he was younger. You probably won't find swaddling to be useful anymore and you will be less likely to be awakened by his quieter late-night stirrings. He’ll start to sleep longer stretches and concentrate that sleep at night but be prepared to get up with him, because he still will be likely to need a nighttime feeding or two.

While all babies wake frequently in the first 6 weeks, some babies start sleeping longer (5 to 6 hours) by the time they are 3 months old; others do not. This period of transition can be very confusing because 3-month-old babies sometimes sleep for longer periods and parents may assume that their babies should always sleep that way. Your baby will show progress toward sleeping longer stretches, but this progress is often of the “one step forward, two steps back” variety as babies hit growth spurts or have other reasons for waking. Around 3 months, parents will start getting pressure from family, friends, and even strangers suggesting that “it’s about time” that their babies should sleep through the night even though most babies don't do so consistently until much later.

Twelve to Sixteen Weeks

Big changes happen as babies get closer to 4 months of age. Most babies start falling asleep in quiet sleep (like their parents) by the time they reach 4 months. This means that they will drift off and stay asleep even when put down right away for nap or nighttime. Babies will also be working hard at developing their “self-soothing” abilities both when they are awake, like sucking on their fingers when they are upset, and at night, by going back to sleep without crying when they wake for a few moments during the night. As with any aspect of being human, there is a great deal of variation in babies’ self soothing skills. Some parents of 4-month-olds are relieved to be sleeping for much longer stretches and other parents with waking babies are wondering what they are "doing wrong." By 4 months, the pressure is really on to reach the ultimate parenting nirvana of sleeping through the night.

Sleep-deprived parents will adopt a wide range of strategies to get more sleep including the use of sleep training methods, co-sleeping, feeding strategies (like weaning from the breast or adding cereal to baby’s bottle against the doctors’ advice), or tag-team efforts for nighttime care. Many parents are willing to try nearly anything to get more rest. Some parents seek advice from parents who claim to have “good sleepers,” hoping to find some answers. Others find that they get advice from everyone whether they want it or not. We have already learned how passionate folks can be about their efforts to get babies to sleep longer. Rather than making any attempt to prescribe the “best way” to get babies to sleep more like their parents, we’ll share (next time) what science tells us about how baby and family characteristics interact to contribute to differences in how babies sleep.

Next time: The Science of Infant Sleep Part III. The Sleeping Relationship

The Science of Infant Sleep Part I: The First 6 Weeks

For nearly all parents, the first six weeks after their babies are born seem to be the longest and toughest in their lives. Struggling to understand their babies' needs, parents are awakened at random intervals day after day and night after endless night. It is no wonder that sleep is the most common topic discussed during early visits to the pediatrician. Parents want know when their babies will sleep through the night. In this first installment of our new series on the science of infant sleep, we'll take a look at the research related to why infants sleep the way they do at different ages and what, if anything, parents can do to help their babies sleep a little more.

Before we start, it is important for parents to know that we are not likely to provide "the answers" to parents' sleep concerns. Instead, we'll bring you up to speed with the latest information from the ever growing body of research related to infant sleep. We're taking a developmental approach as we did with the series on the development of language. We'll start with the prenatal period through the first 6 weeks.

How Do Babies Sleep Before They Are Born?
Since ultrasound technologies have become so advanced, researchers know far more than ever before about babies' prenatal behaviors. Distinct sleep states are likely to appear during the last trimester of pregnancy with "active sleep" (lighter sleep with rapid eye movements) being dominant. As any mother knows, fetal sleep cycles do not necessarily to coincide with their moms' sleep cycles. Many moms nearing delivery will tell you that their babies' movements wake them up at night.

What Controls Newborn Sleep Patterns?
In older children and adults, sleep cycles are controlled by specific areas in our brains based on circadian rhythms sensitive to light/dark cycles and by other mechanisms that increase the need for sleep after longer periods of being awake. These controls make us more likely to sleep during the night but also allow us to sleep during the day if we've gone too long without sleep. Another control system influences how long we remain in different types of sleep. Newborns, who are just as happy to sleep during the day as at night, do not seem to develop effective circadian rhythms until they are around 6 weeks old or later. They also are unable to stay awake for long periods of time. Parents of newborns think that their babies wake and sleep randomly, and for the most part, that's true.

Light Sleep, Dreaming, and Brain Development
Newborns sleep very differently from adults. They fall asleep dreaming and may keep dreaming for 20 or 30 minutes. We fall asleep into a "quiet" state of sleep and dream more later in the night and close to morning. Because dreaming happens in a lighter state of sleep, newborns are much more likely to wake up in response to noises, changes in temperature, and movement. When they are dreaming, newborns can make quite a few little noises and their eyes, facial muscles, arms, and legs will move a lot. Some babies may wake themselves up by their own movements. That's why swaddling, which restricts babies' movements, can help newborns sleep a little better. As babies get older, they don't move around quite as much when they sleep and swaddling is no longer necessary.

The brain activity related to dreaming is important for babies' development. Babies brains develop in part because of brain activity in response to stimulation. While babies are awake, they get stimulation from what they see, hear, feel, and taste. While they are asleep and dreaming, babies' brains are active, allowing for brain development to continue even when babies can't stay awake for very long. As babies get older and are able to stay awake for longer periods of time, they spend less time dreaming. During quiet sleep, babies move very little and they are harder to wake.

How Can Parents Help Their Newborns Sleep Longer?
Newborns spend a great deal of time in a lighter state of sleep, waking relatively easily. This is important for babies development and makes the baby likely to wake to feed, to stay warm, and to move as needed. Newborns are not much influenced by light and dark cycles and need to feed frequently. All this means that newborns are going to wake up...a lot...and there isn't much that parents can do about it. But, there are a few things that can make this exhausting time just a bit easier.

• Swaddling can help newborns sleep a little longer because they are less likely to wake themselves up


• Breastfeeding mothers should avoid caffeine because newborns take much longer to process caffeine than adults do


• Holding newborns who have fallen asleep until after their bodies and eyes stop moving will help babies stay asleep when they are put down. Babies in quiet sleep are much less likely to wake easily


• Parents should pay attention to their newborns' noises to learn when they are still asleep and just making noises versus when they are waking up for feeding or other care

Even using all of these tips, parents of newborns will find that their babies will wake frequently. The very best preparation is to arrange to get some help from family and friends to get you through this tough time. Fortunately, things change quickly and more sleep is just around the corner.

Next Time: Big Changes in Sleep Patterns (6 to 16 weeks)

Baby Behavior Basics Part 1 - Three Reasons Why Babies Don't Sleep Through the Night

One of the most challenging parts of being a new parent is dealing with lack of sleep. Most newborns wake up every 2 hours, around the clock, and many parents desperately wonder when their babies will finally sleep through the night. Tired parents are barraged with the latest gizmos and "systems" to get their babies to sleep longer. Unfortunately, young babies are not supposed to sleep through the night. Waking up at night doesn't make anyone happy, but thankfully, it isn't long before babies naturally sleep for longer stretches. You will get some restful nights, at least until your baby grows up and learns to drive...
No matter what you've heard, there is no one age when all babies will sleep through the night and babies can vary how many times they wake. There's no getting around it; young babies need to wake up at night for some very good reasons and their physiology ensures that's exactly what they do.

Reason 1. Young Babies Wake to Eat
Newborn tummies are very tiny. They can't take in very much at each feeding. No matter how they are being fed, by breast or bottle, babies' rapid growth requires that they are fed frequently. While there is a lot of variability in how much babies can drink at one time, all babies need to eat during the night for the first few weeks of life. As they get bigger, babies can drink more at one time and they don't have to wake as often to eat.

Reason 2. Young Babies Wake Because They Dream
Babies don't sleep like adults. When adults first fall asleep, they fall into a deeper sleep without dreaming, then dream for short periods of time (off and on) throughout the night. Babies fall asleep dreaming (in "rapid eye movement" or REM sleep) and move more slowly to "deeper" forms of sleep, without dreams. For infants, dreaming is vital for normal brain development. While infants dream, blood flows to their brains and neural connections are made. Because it is so important for their development, newborns may dream 30 minutes before they fall into deeper sleep. Premature infants dream even longer and more often than term infants.

Babies, like adults, are more likely to wake up when they are dreaming than if they are in deeper forms of sleep. So, if something happens while they are dreaming, like the phone rings or they are put down into a bassinet, babies are likely to wake. When babies are dreaming, their eyelids will flutter and their faces and bodies will twitch, so it is easy for parents to see when babies stop dreaming and enter deeper forms of sleep. By waiting to put newborns down until after signs of dreaming stop, parents can help their babies stay asleep. By the time babies are 3 or 4 months old, they fall asleep in deeper sleep just like their parents. Often, parents of 4-month-old babies will notice how much "better" their babies are sleeping. Many babies will sleep most of the night around 6 to 9 months of age.

Reason 3. Young Babies Wake to Stay Comfortable and Safe
Babies are born with brand new lungs, muscles, and brains. Sometimes, their little bodies need a little time to get into synch. If babies sleep too deeply, they may get too hot or too cold or they may not wake when they need move their muscles or to get a little more air. This does not mean that babies should wake up all the time. After the first 6 weeks (when almost anything goes), most babies will settle down and sleep 3- to 4-hour stretches. As they get older and their bodies mature, they will sleep even longer.

But..."I Need My Sleep"...
Now that I've given you so much bad news, what can I say to reassure my bleary-eyed readers? I can tell you that all the sleep deprivation is directly supporting the health and development of your wonderful new baby. I can also tell you, that this time passes and before you know it, your baby will be a child, a teen, and suddenly, an adult. You won't believe me, but you'll miss these early months (well, maybe not those first 6 weeks). Meanwhile, rest when you can, even sitting quietly can be helpful. Get as much help as you can with household chores and other responsibilities. Most people love to help new moms.

Just one more thing! Sometimes interrupted sleep can be so stressful that parents may find that they can't think clearly. When we are very tired, the normal checks and balances in our brains don't always work the way they should. If you ever find yourself feeling upset or angry with your baby for waking you up (again!), make sure you take the time to get yourself fully awake before you pick up your baby. Splash some water on your face, have a drink of water, and then care for your baby. When you're awake, you'll be much more likely to make good decisions. If you find that you are often angry or having trouble controlling your emotions, get some help. It is important for you and your baby that you get help. Talk to your doctor or a trusted friend or family member. There are many people who will understand your feelings; you are not alone.
Sweet Dreams!

Next time: Baby Behavior Basics Part 2: The Many Moods of Babies