As every parent knows, the world of newborn sleep is exotic and strange.
Newborns doze at odd times. They seem oblivious to differences between night and day. They awaken frequently.
It's a recipe for exhaustion, but understanding the science of sleep can help you cope.
In this article, I review
• fundamental differences between newborn and adult sleep patterns
• circadian rhythms, and how you can help your baby develop them
• sleep cycles in the newborn, and their implications for putting babies to bed
• tips for preventing newborns from waking up, and
• advice for improving your own sleep
Throughout, I focus on babies under four weeks of age. For information about older infants, see my article on
baby sleep patterns.
If you are looking for information about newborn sleep safety, see these science-based tips for reducing the risk of SIDS.
To the sleepless parent, newborn sleep might seem totally disorganized.
Newborns sleep in short bouts—typically ranging from 30 minutes to 4 hours—at seemingly random times throughout the day and night.
To make things worse for you, newborns awaken easily. This is because they spend a large portion of their sleep time in “active sleep,” a light sleep state characterized by fluttering eyelids; rapid, irregular breathing; occasional body movements; and vocalizations (grunts or brief cries).
Finally, newborns vary greatly in the total amount of time they spend sleeping. In the first few days, the average newborn sleeps between 16-18 hours a day (Iglowstein et al 2002). By four weeks, newborn sleep averages about 14 hours. But the range is considerable. Some four-week-old babies sleep as little as 9 out of 24 hours. Others sleep for 19 hours a day (Iglowstein et al 2002).
If your baby is one of these atypical sleepers, does that mean something is wrong? Not necessarily. Some babies suffer from medical conditions that influence the way they sleep, so if you have concerns you should discuss them with your medical provider. But it appears that many healthy, normal newborns deviate several hours from the average duration of sleep.
The timing of adult sleep is governed by circadian rhythms--physiological changes that follow a 24-hour cycle. Many of these changes are influenced by your exposure to light.
When you expose yourself to sunlight each morning, you help maintain your internal clock. Even if you are sleep-deprived, morning light exposure helps ensure that you will be more alert during the day than you are at night. As the day wears on and darkness falls, your body begins to produce less cortisol (a hormone that keeps you alert) and more melatonin (the hormone of drowsiness). When you expose yourself to bright, artificial lighting in the evening--particularly to lights that include the blue part of the spectrum--you delay these changes and may find it harder to fall asleep (Wahnschaffe et al 2013).
Unfortunately for sleepless parents, newborn sleep is not governed by strong circadian rhythms.
It doesn’t start that way. During pregnancy, fetuses are tuned into their mothers’ physiological cues about day and night. Fetal heart and respiratory rates speed up when Mom is active and slow down when she is sleeping (Mirmiran et al 2003). Such changes may be influenced by maternal hormones, particularly melatonin. Maternal melatonin passes through the placenta and may direct the fetus’ internal clock (Torres-Farfan et al 2006).
But after birth, this intimate hormonal connection is broken, and newborns must rely on their own internal clocks. But they haven’t yet developed their own circadian rhythms of melatonin production (Kennaway 1996). Nor have newborns developed circadian rhythms for the production of cortisol.
Instead, the life of the newborn revolves around a new problem: Getting fed. Newborn sleep patterns are shaped by the length of time it takes them to feed, digest, and become hungry again.
For most newborns, this means feeding every few hours. Sleep episodes are brief and spaced in fairly regular intervals around the clock.
When does it end?
Most infants take about 12 weeks to show day-night rhythms in the production of melatonin, the “sleep hormone” (Rivkees 2003). Circadian changes in cortisol--a hormone that helps regulate waking--may take even longer to emerge (Rivkees 2003). And, overall, babies may take 3-5 months before they “settle” at night--meaning that they sleep for more than 5 hours at a stretch (Jenni et al 2006; Pinilla and Birch 1993).
Nevertheless, newborn sleep isn’t completely divorced from the natural rhythms of the 24-hour day. Studies show that circadian rhythms begin developing in the first days after birth.
For example, German and Japanese studies have reported that newborns sleep more at night than they do during the day (Freudigman and Thoman 1998; Korte 2004; Matsuoka et al 1991).
And scientific evidence suggests that even newborns are receptive to environmental cues about time. You can take advantage of this fact to help shape newborn sleep patterns.
• Make your baby a part of your daily routine. Some researchers argue that social cues have the biggest impact on newborn sleep patterns (Custodio et al 2007; Lorh et al 1999). When mothers include their newborns in their daily activities, newborn sleep patterns adapt more rapidly to the 24-hour day. One study took continuous measurements of mother-infant activity patterns for four months after birth. Newborns who were active at the same time of day as their mothers quickly adapted to the daily schedule (Wulff and Siegmund 2002).
• Reduce stimulation at night. When your baby wakes for night time feedings, keep activity to a minimum. Make as little noise as possible, and avoid moving your baby around. Ideally, you want to avoid waking her “all the way up.” But if that’s not possible, at least try to minimize the hustle and bustle.
• Expose your newborn to natural lighting patterns. Light cues may not instantly program your baby's clock, but they help. In a study of preterm infants kept in hospital wards, babies exposed to natural lighting patterns--brighter during the day, darker during the night--adapted to the 24-hour cycle more quickly than those exposed to constant, low levels of light (Rivkees et al 2004). In another study of full-term infants, babies who got more afternoon sunlight slept better at night (Harrison 2004). And in case you are wondering, getting outdoors might make an important difference. Babies who get outside experience much higher light levels, and may develop stronger circadian rhythms as a result (Tsai et al 2012).
• Try infant massage. One study reports that newborns who received 14 days of massage therapy (beginning when they were about 10 days old) showed more mature sleep patterns in later weeks. At 12 weeks, the massaged infants had higher levels of nocturnal melatonin (Ferber 2002). Was this a fluke? More research is needed (Bennett et al 2013), but given the soothing nature of gentle, affectionate physical contact, it seems safe to try.
• Consider keeping track of the time of day you extract and store breast milk for future use. Breast milk contains tryptophan, an amino acid that is used by the body to manufacture melatonin. Tryptophan levels rise and fall according to maternal circadian rhythms, and when infants consume tryptophan before bedtime, they fall asleep faster (Steinberg et al 1992). It’s therefore possible that breastfeeding helps newborn sleep patterns synchronize with the 24-hour day (Cubero et al 2005). This hypothesis was tested by feeding infants formula fortified with varying concentrations of tryptophan. When infants were given low levels of tryptophan during the day and high concentrations at night (mimicking the natural fluctuations of breast milk), infants fell asleep faster at night and got more sleep overall (Cubero et al 2007).
When adults fall asleep, we pass through a series of sleep stages, including bouts of deep (“slow wave”) sleep, and, finally, REM (rapid eye movement) sleep. REM is famous for its association with dreaming. But it’s also known for its distinctive pattern of brain activity, which resembles that of the busy, waking brain. Adults are much more likely to awaken during REM than they are during deep sleep.
At the end of a REM session, the sleep cycle is completed. Adults either wake up, or begin another sleep cycle. A single sleep cycle lasts about 90-100 minutes.
Newborn sleep follows a different pattern. When a newborn first falls asleep, she enters into immediately into “active sleep.” This rather restless sleep state is similar to REM (rapid eye movement) sleep in adults. Just as adults are more likely to awaken during REM, newborns are more likely to awaken during active sleep (Anders 1979; McNamara et al 2002).
Newborns may remain in this active sleep state for 25 minutes or more, after which they slip into a deeper sleep state known as “quiet sleep.” Compared to active sleep, quiet sleep is characterized by slower, more rhythmic breathing, little movement, and no eyelid fluttering.
Babies are less likely to awaken during quiet sleep, but this situation doesn’t last long. After about 50 minutes, the sleep cycle ends. Newborns then either awaken or begin another bout of active sleep (Anders 1979; McNamara et al 2002).
So newborn sleep is different in several important ways. For one thing, newborns spend much more time in active sleep than adults spend in REM. Whereas adults spend only 20% of their sleep time in REM, newborns spend at least 50% of their sleep time in active sleep. In fact, several studies suggest that, over the course of a 24 hour day, newborns spent as much as 75% of their sleep time in active sleep (e.g., Poblano et al 2007; Sadeh et al 1996). As a result, newborns spend a much greater proportion of the time “sleeping light.”
For another thing, newborn sleep cycles are much shorter than are adult sleep cycles. Instead of 90-100 minutes, the average newborn sleep cycles lasts only 50 minutes or so. As a result, newborns are vulnerable to awakening much more frequently.
This sounds like a raw deal for parents. But we should keep a couple things in mind.
First, it's normal for adults and babies alike to experience frequent arousals during sleep, and most of these arousals do not result in our waking up "all the way." A baby who seems to be waking up may, if left alone, go back to sleep very rapidly.
Second, newborns probably benefit from being light sleepers. Having a low threshold of arousal may protect babies from SIDS. And active sleep might be crucial for a newborn’s brain development (Heraghty et al 2008; Seigel 2005).
Of course, this doesn't mean that active sleep is good and quiet sleep is bad. Babies in active sleep may experience more heart rate irregularities and more episodes of sleep apnea, conditions which may put babies at higher risk for SIDS. There is also evidence that SIDS cases have special problems arousing from active sleep (Kato et al 2003). Conversely, the analog of quiet sleep in older people -- non-REM sleep -- seems to be important for good health and memory consolidation. Perhaps it plays a similar role in newborns.
• Don't rush in the moment you think your baby has awakened. As noted above, babies experience frequent arousals, but that doesn't mean they are doomed to wake up "all the way" every few minutes. Babies often jerk, sigh, or vocalize during partial arousals. If you avoid stimulating them during these moments, they may go back to sleep on their own.
• Try to feed your baby milk or formula that includes DHA. DHA is a fatty acid found in fish oil and other dietary sources. It’s important for brain development, and may play a role in shaping sleep patterns as well. In one study, children who consumed low levels of DHA had reduced amount of slow-wave (deep) sleep (Faglioli et al 1989). In another study, pregnant women with higher blood levels of DHA gave birth to babies who spent more time in quiet sleep (Cheruku et al 2002). DHA is found in breast milk, so it’s seems plausible that boosting a nursing mother's DHA intake could improve a newborn’s sleep patterns. If you bottle-feed, find a baby formula that contains DHA.
• Tank up the baby before you go to sleep. Whether you breastfeed or bottle-fed, try to give the baby an especially large meal before your own bedtime. This will encourage your baby to sleep longer.
• Check out my article on baby sleep aids, which includes more tips for improving newborn sleep.
Newborn sleep patterns take their toll on parents. In a study tracking the sleep patterns of mothers from pregnancy through the postpartum period, maternal sleep worsened after childbirth and continued to deteriorate until about 12 weeks postpartum (Kang et al 2002)—-the time when newborn sleep patterns begin to show marked circadian rhythms (Nishihara et al 2000).
Twelve weeks isn’t forever, but it can seem like it when you are severely sleep restricted. As you struggle to cope with newborn sleep patterns, don’t forget to look after yourself. Here are some tips to help you cope.
• Too wired to "sleep when the baby sleeps"? If so, keep in mind that quiet resting is better than nothing. In fact, if you are lying down with your eyes closed, you might be asleep without realizing it. In numerous lab studies, subjects who were awakened from the first stage of sleep often denied that they were asleep at all (Dement and Vaughan 1999). A nap that consists only of stage 1 sleep won't help you improve your reaction times, but it will probably make you feel less tired. And if you manage to slip into the second stage of sleep -- even for just 3 minutes -- your nap may have recuperative effects (Hayashi et al 2005).
• Don't waste energy on self-reproach or criticism from other people. You might be doing everything you can to get more sleep, and still be stuck with a baby who sleeps less than average. Research suggests that the amount of sleep we get at night is strongly influenced by genetics (Touchette et al 2013).
• Don't assume that breastfeeding will make you more sleepless than formula feeding. One study reported that the parents of breastfed babies averaged 40-45 minutes more sleep time than did the parents of formula-fed babies (Doan et al 2007).
• If you are breastfeeding, you are likely to get more sleep if you keep baby nearby. The World Health Organization recommends that you babies share a bedroom with their parents, and it's a recommendation that makes breastfeeding less disruptive. A recent study found that breastfeeding women got more sleep when they co-slept with baby (Quillin and Glenn 2004). In fact, mothers who co-slept and breastfed got more sleep than did mothers who bottle-fed their babies (Quillin and Glenn 2004).
• If your baby is asleep, don’t worry about changing diapers. If your baby can’t sleep because she needs a diaper change, she’ll let you know. And a little urine is unlikely to awaken her anyway. In a recent experiment, researchers injected water into the diapers of sleeping infants to see if this would wake them up (Zotter et al 2007). It didn’t.
• Get sunlight and avoid artificial lighting at night. Make sure you expose yourself and your baby to bright light during the day. And keep lights out—-or at least dimmed—-after sunset. As noted above, natural lighting helps influence newborn sleep patterns. But it also helps you keep your own circadian rhythms from drifting, which is important if you are going avoid insomnia and be a source of day-time cues for your newborn.
• Let a friend or family member watch your baby while you take a nap, even if this means your breastfed baby will take some of his meals from a bottle. Lactation experts often discourage breastfeeding mothers from bottle feeding babies for the first 3-4 weeks. The worry is that supplemental feeds will lead to a decreased milk supply and endanger successful breastfeeding in the long-term. But you need to balance this against the negative effects of severe sleep restriction. Lack of sleep puts parents at increased risk of illness and postpartum depression, which is bad for parents and babies. If you are at the end of your rope, you need to get help.
• Trust your instincts. If something feels wrong with you or the baby, talk to your physician.
• Remember that things will get better. Newborns have special sleep patterns and special needs. But things will start to get better around 12 weeks postpartum.
For more information about babies and sleep, see these fully-referenced Parenting Science articles.
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