Newborns tend to sleep a lot—at least for the first couple of weeks, which comes as a relief to their shell-shocked parents. The average newborn crams in around sixteen to eighteen hours of sleep per day, which tends to drop to around fourteen to fifteen hours by the time they are a month old. At this stage, a newborn’s sleep patterns are more influenced by the fullness of its belly than by whether it’s light or dark outside, but by two or three months, it is beginning to grasp the notion of night and day.
As anyone who has suffered from jet lag will know, we humans have a firmly entrenched body clock, which means our bodies respond differently depending on what time of day it is. As night falls, we produce more of the sleep-promoting hormone melatonin, which makes us increasingly drowsy as the evening progresses.
So what about babies? The body’s master clock is located at the front of the brain in an area called the suprechiasmic nucleus (SCN). It is in direct contact with the eyes and can be shifted forward or backward by exposure to bright light, which is how the body manages to reset itself within a couple of days when you travel across time zones. The SCN is thought to have developed by around twenty weeks of pregnancy, and fetuses do show differences in their heart rates, breathing movements, and hormone levels depending on the time of day—although these rhythms are probably being driven by signals from the mother, rather than being self-generated.
The SCN continues gradually to mature after birth. For the first few weeks, a baby’s sleep is distributed pretty evenly over twenty-four hours, but by six weeks, most babies are slightly more active during the day and sleepier at night, and by three months, higher levels of melatonin can be detected in a baby’s blood at night.
Your grandmother may tell you that a good way of getting a baby to sleep through the night is to stick it outside in the garden during the daytime. Although you may be suspicious that this is simply a ruse for the mother to get some peace and quiet, Grandma might be correct: Research has shown that two- to three- month-olds who are exposed to plenty of bright sunlight during the day sleep better at night. This is probably for the same reason that people overcome jet lag faster if they get outdoors into the sunshine—bright light plays a crucial role in setting the body’s central clock and ensuring that it runs on time.
Most people broadly fall into one of two categories: early birds, who wake up early and like to turn in to bed soon after it gets dark; and night owls, who like to slumber through the morning and are more active during the evening. Just which category you fall into seems to be inherited, to some degree, which is good news for owl-like parents who dread being woken up by a “dawn baby chorus.”
Interestingly, just how much of an early bird or night owl someone becomes also seems to be driven by the season in which they were born. Several European and Canadian studies have suggested that babies born during spring and summer are more likely to turn into night owls, while those born in autumn and winter are more likely to become early birds. The effect was particularly strong among babies born in Montreal during late September and October, a high proportion of whom became morning types. This might be explained by the fact that the months from October to December tend to be gloomy for those living in Montreal, with the lowest average hours of sunshine over the year. Researchers believe that there may be a critical window of time after birth when the body clock is extremely sensitive to light and its future pattern can be set. Studies in rats have suggested that those raised in dim light are more sensitive to its effects, finding it harder to sleep during daylight, for example.
What about other aspects of sleep? Much of what we know about the inheritance of sleep patterns comes from studies of identical twins. Because they share the same genes, you can look at differences in twins’ behavior to calculate what proportion comes down to genetics and what proportion can be attributed to external factors such as how they were raised, the hours they work, and their social lives. Twin studies have suggested that approximately a third of the difference in the amount of sleep people need, the amount of time it takes people to fall asleep, and how often they wake during the night can be explained by genetic factors. This means that although a baby’s sleep patterns should show some relation to how you sleep as parents, external factors have a greater influence.
The average newborn sleeps sixteen to eighteen hours a day, but there is a lot of variability among individuals. One large study found that some newborns slept for just nine hours per day, while others clocked up a whopping nineteen hours of sleep over twenty-four hours. The same is true at two months of age, with some babies sleeping for just twelve hours a day and others managing twenty-one.
The good news for parents who find themselves blessed with a sleepy newborn is that the amount of sleep babies need and their general degree of fussiness seems to remain relatively consistent as they get older—although how often they wake, feed, and cry can vary according to what’s going on in their lives.
As for sleeping through the night, parents shouldn’t expect too much too soon. Though studies have found that up to three quarters of babies are sleeping through the night by twelve weeks of age, what “sleeping through the night” means to researchers is five hours of undisturbed sleep in a row—a definition I suspect most parents would find reason to quibble with. A review of twenty-six studies focusing on babies’ sleep found that just 37 percent of healthy three-month-olds regularly slept for eight hours at night without waking their parents.
While the amount of sleep a baby needs is inherited, to some degree, research suggests that parents’ interactions with the baby play a crucial role in terms of getting it to sleep through the night. So how do you encourage your baby to fall into the sleepy category?
Most sleep researchers agree that introducing a consistent bedtime routine in the run-up to bed, such as brushing teeth, taking a bath, and reading a story, helps babies to fall asleep, as do waking them at the same time each morning (assuming they don’t wake you first) and ensuring that they get some kind of physical exercise during the day. Making a clear distinction between night- and daytime seems to help, for example, by settling babies for naps in rooms that aren’t too dark during the daytime and minimizing interaction at night. At least one study found that babies exposed to more natural light in the early afternoon slept better at night than those exposed to less.
Babies are creatures of habit and quickly learn to associate certain cues with sleep. This means that if parents aren’t careful, they can form bad habits. A review of studies on night waking and other bedtime issues found that some of the most common problems included needing to be rocked or held or for the parent to be present in order for the baby to fall asleep; needing to be fed to sleep; and habitually waking several times during the night. It is unlikely that parents set out to form such habits; more likely, they are born out of desperation—taking a baby into bed and breast-feeding it back to sleep when it wakes for the fifth hour in a row, for example.
Trying to prevent bad habits from forming in the first place can be easier than trying to break them once they’ve become established. Most experts agree that parents should try to put a baby down in its crib while still awake so the baby doesn’t become reliant on their presence in order to fall asleep.
There are a few other tactics that parents can use to try to establish good sleep habits from a tender age. A study of 610 women found that those who were taught the following techniques when their babies were ten days old were 10 percent more likely to have a baby who slept consistently for five hours or more at twelve weeks, compared to parents who received little or no advice.
(The next eight points are taken from “Use of a behavioral programme in the first three months to prevent infant crying and sleeping problems,” Journal of Paediatrics and Child Health, June 2001, vol. 37, issue 3, pp. 289–97.)
1. During the daytime, feed your baby whenever she seems hungry, and spend plenty of time interacting with her. Try to bathe her at around the same time each day.
2. Encourage your baby to take a “focal feed”—either a longer than normal breast-feed or a larger formula feed—between ten P.M. and midnight.
3. If your baby is still awake after feeding and changing, try not to hold, rock, or nurse him to sleep. Instead, put him into the crib while he’s still awake and leave him to settle himself. Lights should be dimmed, although it doesn’t have to be completely dark.
4. If your baby doesn’t settle, check the following:
(a) Does the diaper need changing?
(b) Does he need to be burped?
(c) Is he too hot or cold?
(d) Stroke and talk softly to your baby. If necessary, pick him up and have a cuddle.
Give each tactic at least ten minutes to work before moving on to the next one.
5. Try to distinguish between genuine crying and fretting in order to reduce the number of times your baby is picked up at night. Babies may fret before settling to sleep and don’t always need further attention.
6. Try to keep the lights dimmed during night feeds. Respond to your baby’s needs by changing the diaper or feeding her and then settle her back to bed. If your baby doesn’t settle, work through step 4 again. Avoid playing or socializing with your baby.
7. If your baby is waking more than every three to four hours at night, he probably don’t need the diaper changed every time.
8. Make nights as uninteresting as possible for your baby. Nighttime is for sleeping.
Once babies were three weeks old (so long as they were healthy and gaining weight), moms were told to start lengthening the time between night feeds. This didn’t mean leaving babies to “cry it out” for long periods on their own, but teaching them to dissociate waking and feeding so they didn’t automatically expect to be fed if they woke at night. Delaying tactics included changing the diaper, resettling them back to sleep, patting, or carrying them. (Note: The current advice from breast-feeding experts is to resist cutting out night feeds for at least the first few weeks of breast-feeding, when feeding on demand is necessary to establish a good and regular supply of milk.)
Many of the women in this study didn’t bother with the prolonged evening feed, presumably because they felt uneasy about waking a baby who was already asleep. They also took closer to six weeks to start lengthening the space between night feeds. Still, the fact that there was a difference between the groups suggests there are measures that parents can take to boost nighttime sleep.
The use of focal feeds (also known as “dream feeds”) was investigated in a separate (although small) study of twenty-six women and their newborn babies, half of whom were told to give an extra-large feed between ten P.M. and midnight and then to gradually increase the amount of time between night feeds by resettling the baby without feeding if it woke at night by swaddling or changing the diaper. The mothers also tried to settle babies in the crib for daytime naps rather than carrying them and tried to maximize differences between night and daytime (for example, by not using blackout blinds during the day and trying to engage as little as possible at night).
By the time these babies reached eight weeks, all of those following the program were sleeping for regular five-hour stretches at night, compared to just 23 percent of babies who weren’t. Even though the babies were feeding less frequently at night, the researchers found that their weight gain and overall milk intake over twenty-four hours was the same as for babies who fed more often. They seemed to make up for the reduced night feeds by drinking more milk in the early morning.
Co-sleeping is the norm for around 90 percent of the world’s population, yet child-care experts in many Western countries advise against it. Part of the reason is safety, since studies have linked co-sleeping to a slightly increased risk of sudden infant death syndrome (SIDS), although steps can be taken to reduce the risk. However, there’s also a prevailing fear that if babies start off sleeping in the parental bed, it will become impossible to kick them out of it.
Despite these fears, co-sleeping seems to be on the increase in many Western countries. One survey of U.S. parents found that the number of mothers co-sleeping with their baby for all or part of the night doubled between 1993 and 2000 to 12.8 percent, while a separate study reported that nearly half of UK mothers share a bed with their baby at some point during the first month of its life; this drops to 29 percent when babies are three months old.
Those who champion co-sleeping claim that it makes breast-feeding easier, boosts the baby’s development, and promotes bonding—and that it actually reduces the risk of SIDS, because parents can keep a closer eye on their baby. It is true that studies have found a higher rate of breast-feeding among mothers who share a bed with their baby compared to babies who sleep alone, although it’s difficult to disentangle the fact that many women who choose to co-sleep are also keen to breast-feed. One small study that filmed babies either sharing a bed with their moms, lying in an open-sided crib that was attached to the bed, or lying in a separate cot found that those in the bed or crib attempted to feed more often and had more successful feeds than those in the separate cot, which could help establish a better milk supply. However, a separate study found no difference in the rate at which babies gained weight between co-sleepers and babies who slept in cribs.
Evidence that co-sleeping benefits brain development is also patchy. One study that followed 205 children from birth through to the age of eighteen found better cognitive performance in areas such as memory and decision-making among those who co-slept as babies when they reached the age of six, but the effect was small, and there was no difference in their cognitive, social, emotional or developmental maturity when they were assessed again at age eighteen. Meanwhile, a separate study of 175 babies who slept alone and 29 babies who routinely co-slept found that the solitary sleepers were generally less irritable than the co-sleepers when they were assessed at four months of age.
A key problem is that the definition of co-sleeping varies among researchers, health professionals, and parents. Researchers tend to define co-sleeping as sharing the same room rather than the same bed, while health professionals use co-sleeping to describe bed-sharing. Those who champion co-sleeping often cite a study that found higher self-esteem among women who co-slept as young children, but it actually looked at women who spent several years sleeping in their parents’ bedroom, not necessarily sharing a bed with them. The fact is that very little good-quality research has been done on the physical or emotional benefits of co-sleeping, so the jury is out.
The issue of safety is also far from straightforward. Those studies that have looked at the characteristics of babies who died from SIDS have identified co-sleeping as a possible contributing factor, but it is difficult to disentangle it from other factors that go alongside bed-sharing, such as poverty, parents who smoke, or the baby sleeping on its front. Depending on the characteristics of individual families, estimates on the risk of SIDS for babies who share a bed with their parents ranges from no increased risk among nonsmoking families to a twelve-fold increased risk for babies sleeping on a sofa with a parent who smokes.
Given this uncertainty, it probably comes down to individual parents to decide what works best for them. If you do want to share a bed with your baby, factors that seem to increase the risk of SIDS include smoking (particularly if the mother smoked during pregnancy, which may affect the development of the brain), sleeping with the baby on a sofa, and consuming drugs or alcohol. Overheating and smothering with pillows are possible risks, so take steps to prevent these from happening.
No subject is more divisive among parents than controlled crying. Those who support it claim the pain is only temporary and that teaching babies to settle themselves is one of the greatest gifts a parent can give. Those who oppose it believe that leaving a child to cry is tantamount to cruelty and may cause lasting damage. Parenting books also disagree on the matter. Out of thirty-nine books on infant sleep that are currently available in the U.S., twenty-four endorse or advocate controlled crying as a means of teaching children to sleep, while twelve oppose or warn against it. The remainder take no position.
In terms of teaching babies to sleep, controlled crying does seem to work, although other, less severe methods appear to be equally effective. In 2006, the American Academy of Sleep Medicine (AASM) published a review of fifty-two studies that evaluated the effectiveness of various methods of sleep training, many of which involved some degree of controlled crying.
In its strictest form, controlled crying (also known as “extinction” or “crying it out”) involves ignoring all crying, tantrums, and calls for parents, unless the child is hurt, ill, or in danger—and doing this every night, no matter how long the crying lasts. The claim is that if you cave in and respond to the child, it will simply learn to cry longer the next time. Softer variations include leaving progressively longer intervals before going in and reassuring the child, then leaving; or staying in the room with the child but ignoring its cries. The ultimate goal is to teach the child to develop its own self-soothing skills so it can fall asleep independently of its parents.
Other strategies for teaching children to sleep involve establishing positive bedtime routines, such as taking a bath and reading a story; scheduled awakenings, when a child is deliberately roused fifteen to thirty minutes before it would usually wake up, then settled back down while semi-conscious; and educating parents about establishing regular naptimes, consistent bedtime routines, and putting babies into their cribs when they’re drowsy but not asleep.
According to the AASM review, all of these strategies worked to some degree, and of the few studies that conducted head-to-head comparisons of the different methods, there was little evidence to suggest that any were vastly superior in terms of effectiveness in the long run. Strict controlled crying seemed to work faster than scheduled awakenings in babies who woke often at night, but the different forms of controlled crying seemed to be pretty much on a level playing field in terms of teaching babies to sleep, along with establishing positive bedtime routines.
Parents should consider a baby’s age before considering any form of sleep training.
At least two randomized controlled trials have found that trying to use any form of sleep training on babies younger than three months is ineffective and doesn’t decrease crying. There are steps you can take to prevent bad habits from forming (see 100: “How can I get my baby to sleep through the night?”).
Most experts agree that controlled crying shouldn’t be used on babies under six months of age, as they may need to feed during the night. You might try working on establishing positive bedtime routines and making sure your baby gets regular naps during the day—or try scheduled awakenings if your baby wakes often during the night.
If you and your baby still aren’t getting enough sleep and you’re considering controlled crying, you can take comfort from several studies that have investigated whether it has any long-term adverse effects. The general conclusion is that, overall, sleep training makes babies more secure, more predictable, and less irritable than they were before treatment. An Australian study of 225 babies whose parents used controlled crying at eight to ten months of age found that controlled crying reduced babies’ sleep problems by around 30 percent within four months, although 15 percent of babies didn’t respond to it. When parents completed questionnaires assessing their children’s emotional and behavioral development at various points until the age of six, there seemed to be no difference between children who had received sleep training as infants and those who hadn’t.
There is one final note of caution. In 2012, a study was published suggesting that controlled crying did have a short-term physical effect on a baby’s stress levels even after it had stopped crying out for its parents at night. Wendy Middlemiss and her colleagues at the University of North Texas measured daily levels of the stress hormone cortisol in twenty-four babies aged four to ten months as they underwent a five-day residential sleep-training program at a hospital in New Zealand. The program involved a typical regime of controlled crying in which mother and baby were separated at bedtime and a nurse settled the baby into its crib. It was then left to fall asleep by itself, although a nurse would go in and check on the baby every ten minutes if it continued to cry. The mother was not allowed to comfort the baby but was in a nearby room and could hear its cries.
Levels of cortisol were similar in moms and babies before sleep training commenced; perhaps unsurprisingly, they rose considerably after the first night. The same thing happened on the second night, but by the third night, the babies had learned to settle themselves to sleep and cried considerably less. At this point, the mothers’ cortisol levels began to fall, and they expressed relief that their babies were beginning to respond to sleep training and they were finally getting a decent night’s sleep. However, measurements of cortisol revealed a disconnection between the babies’ outwardly calm appearance and what was going on inside. Although the babies no longer cried, they continued to experience high levels of cortisol, similar to those on the first night. This might suggest that, though they’re calm on the outside, they are unhappy on the inside.
No further measures of cortisol were taken after the program ended, so it’s impossible to know at this stage whether the babies’ stress levels eventually normalized—although the fact that other studies have found no lasting negative effects from controlled crying is somewhat reassuring. Further studies are clearly needed to confirm how long babies remain stressed. “It may well be that the infant is still in a transition period and will be fine,” says Middlemiss, “but the disturbing thing for me is that the mother can’t choose whether or not to respond to the infant’s distress, because she can’t see it.”
Given that less severe forms of controlled crying seem to be just as effective as the strict version in terms of curbing sleep problems, I’d personally be tempted to try one of these variations first.
As with controlled crying, parents tend to split over whether babies should adhere to strict schedules or have Mom and Dad at their beck and call. In The New Contented Little Baby Book, Gina Ford suggests that in order to get your baby to sleep through the night from an early age, you need to establish the right associations and structure your baby’s feeds and naps from the day you arrive home from the hospital. At the opposite end of the spectrum, attachment-parenting gurus such as Jean Liedloff advocate prolonged holding, frequent breast-feeding, co-sleeping, and rapidly responding to a baby’s cries in order to foster strong emotional bonds between mother and baby.
In a recent study, Ian St. James-Roberts and colleagues at the Thomas Coram Research Unit in London compared the impact of these very different parenting styles on the amount of time young babies spent crying and sleeping. They recruited three groups of parents: one from London, one from Copenhagen, and a third group of mixed-nationality parents who practiced an extreme form of attachment parenting (also known as proximal care), in which babies were carried around for much of the day, breast-fed on demand, and parents rapidly responded to cries. Parents were asked to keep daily diaries of what they did and how their babies responded at various points during the baby’s first twelve weeks. They also completed questionnaires about infant feeding and sleeping patterns. Parents in the proximal-care group spent around sixteen and a half hours a day holding their ten-day-old babies and fed them fourteen times a day, while London parents tended toward the tough-love approach, holding babies around half this amount of time and spacing out feeds so they ate eleven times a day. Babies in Copenhagen fell somewhere in between, held for nearly ten hours a day and fed twelve times. London parents also left their baby to cry for around three times longer each day than either the Copenhagen or proximal-care parents.
At twelve weeks of age, 85 percent of proximal-care and 70 percent of Copenhagen babies were still exclusively breast-fed, compared to just 37 percent of London babies (though this could be for cultural reasons), and most proximal-care parents co-slept with their infants, while just 16 percent of Copenhagen parents and 9 percent of London parents did the same.
So how did the babies respond? Those living in London spent around 50 percent more time fussing and crying than those in the other groups, though there was no difference in bouts of inconsolable crying (see 89: “What causes colic?”). When parents were asked how many nights in the past week their twelve-week-old baby had slept for five hours or more, London and Copenhagen parents reported around five such nights, while proximal-care parents reported just three and a half nights on average.
This is just one study, but it does suggest that the extreme form of proximal care is more likely to result in frazzled parents, without any obvious benefit in terms of sleep quality or the amount of time babies spend crying, compared to the more moderate approach of the Danes. By the parents quickly responding to their baby’s cries, the Danish babies spent less time crying overall (although we don’t know if extra crying is actually harmful to babies), and they seemed to sleep just as well. On the other hand, the tough-love approach of the London parents didn’t mean they got any less sleep—they just may have had to put up with sore eardrums during the day.