How to Get Your Baby to Sleep Through the Night

Most babies can sleep a sustained stretch of about eight hours by around six months of age, but getting there depends on a mix of biological readiness, consistent habits, and realistic expectations about what “sleeping through the night” actually means. The phrase itself is surprisingly misleading, and the gap between what parents expect and what infant sleep researchers measure is one of the biggest sources of frustration in early parenthood. What follows is a practical, evidence-based look at how infant sleep develops, what you can do to support it, and where the science is more nuanced than the advice books suggest.

What “Sleeping Through the Night” Really Means

One of the earliest and most cited definitions of sleeping through the night came from a 1957 study that set the bar at sleeping from midnight to 5 a.m. That five-hour window was enough to count. In a survey of parents, over 80 percent disagreed with that definition, reporting that they expected sleeping through the night to mean something closer to 8 p.m. to 6:30 a.m., with an average expected stretch of about nine and a half hours.¹ That mismatch matters. When a pediatrician says a baby “should” be sleeping through the night by a certain age, they may be referencing a very different standard than the one keeping you awake.

A review of the research literature found that most infants can sustain eight hours of sleep by about six months and nine or more hours after that, which actually meets more demanding criteria than the old midnight-to-five standard.² But “can” and “will” are different things. Your baby’s ability to produce a long stretch of consolidated sleep depends on their neurological maturity, feeding patterns, and whether they have learned to resettle themselves when they briefly wake between sleep cycles, which all babies do.

When Your Baby’s Brain Is Ready

Newborns do not have a functioning circadian clock. Their bodies cannot distinguish day from night on a hormonal level, and no amount of routine or environment tweaking changes that in the first few weeks. Research tracking the emergence of circadian rhythms in human infants found that the body-temperature rhythm appears first, within the first week of life. The wake rhythm becomes statistically detectable around day 45, roughly the same time melatonin starts rising in the evening. The sleep rhythm lags behind, not reaching significance until after day 56.³

What this means practically is that for the first two months, your baby is not ignoring your efforts to establish a day-night pattern. Their brain literally cannot produce one yet. The circadian system comes online gradually, and melatonin production, which helps signal sleepiness in the evening, ramps up around six to eight weeks. Expecting consolidated nighttime sleep before that biological switch flips is setting yourself up for disappointment. Once it does flip, though, you can start reinforcing the signal with environmental cues like bright light during the day and dim light in the evening.

The Power of a Consistent Bedtime Routine

If there is one intervention that has broad support and almost no controversy, it is establishing a predictable bedtime routine. A study of infants and toddlers found that introducing a consistent nightly routine led to significant improvements in how quickly children fell asleep, how often they woke during the night, and how long they stayed awake after waking. Sleep continuity increased, and fewer mothers rated their child’s sleep as problematic. Notably, maternal mood also improved.⁴

A separate large-scale study confirmed a dose-dependent relationship: the more consistently a bedtime routine was practiced, the better the sleep outcomes, and the younger the child was when the routine started, the stronger the effect.⁵ A conceptual model of bedtime routines identifies the key components as spanning nutrition (a final feeding or healthy snack), hygiene (a bath, brushing teeth), communication (reading, singing), and physical contact (cuddling, rocking, massage).⁶ You do not need to do all of these every single night, but the consistency and predictability are what matter. A bath, a book, a feed, and lights out, done in roughly the same order at roughly the same time, gives your baby’s brain a reliable set of cues that sleep is coming.

Sleep Training Methods and What the Evidence Shows

Sleep training is one of the most debated topics in parenting, but the research on it is more settled than the internet arguments suggest. A randomized controlled trial tested two common approaches on infants aged six to sixteen months. Graduated extinction, sometimes called “Ferber-style” training, involves putting your baby down awake and responding to crying at increasing intervals. Bedtime fading involves temporarily pushing bedtime later so the baby is more tired, then gradually shifting it earlier. Both methods produced significant improvements in how quickly babies fell asleep. Graduated extinction also led to large decreases in the number of night wakings and the total time spent awake after initially falling asleep.⁷

The trial also measured salivary cortisol (a stress hormone) in the babies over the study period and found no adverse stress responses compared to the control group. That finding is worth pausing on, because the most common objection to sleep training is that it causes harmful stress. A separate, smaller study did find something more complicated: after three days of an extinction-based program, babies had stopped crying at bedtime, but their cortisol levels remained elevated even though they were no longer showing behavioral distress.⁸ That study gets cited often as evidence that sleep training causes hidden harm, but it involved only 25 infants in an inpatient setting using full (unmodified) extinction, which is not what most families practice at home. And the cortisol finding was a snapshot on one day, not evidence of a lasting pattern.

Does Sleep Training Affect Your Relationship With Your Baby?

The most rigorous answer to this question comes from a five-year follow-up of a randomized trial that tracked families who had received a sleep training intervention against families who had not. At the five-year mark, there were no differences between the groups on child-parent closeness, conflict, the overall quality of the relationship, or signs of disinhibited attachment.⁹ This is important because the attachment concern is the main reason parents hesitate. Based on the available long-term evidence, graduated extinction and similar approaches do not appear to harm the parent-child bond or the child’s emotional development.

That said, sleep training is not mandatory and is not appropriate for every family or every baby. Some babies respond quickly and dramatically; others do not. If your baby is younger than about four months, sleep training is generally not recommended because the circadian system is still immature. And if the idea of any crying feels unbearable to you, gentler approaches like bedtime fading, the “chair method” (sitting near the crib and gradually moving farther away), or simply optimizing the bedtime routine can still make a meaningful difference, even if they work more slowly.

How Feeding Affects Night Sleep

The relationship between feeding and sleep is more tangled than the common advice (“just give a bigger bottle before bed”) suggests. Breastfed infants actually tend to have longer nighttime sleep durations at multiple ages compared to formula-fed infants, but they also wake more often between six and twelve months.¹⁰ A study of a Chinese population found a similar pattern: exclusively formula-fed babies had slightly more total sleep per 24 hours and fewer night wakings, but the gap between feeding methods narrowed as infants got older.¹¹ In other words, how you feed your baby matters less for sleep than you might think, and the differences become smaller with time.

What about starting solid foods earlier? A secondary analysis of a large randomized trial found that infants who were introduced to solids alongside breastfeeding at three months (rather than waiting until six months) slept about 17 minutes longer per night by six months and woke slightly less frequently. Parents in the later-introduction group were also nearly twice as likely to report serious sleep problems.¹² Seventeen minutes may not sound life-changing, but for sleep-deprived parents, it can feel substantial. However, another study offered a useful caveat: infants who consumed more calories from milk or solids during the day were less likely to feed at night, but they were not less likely to wake.¹³ So packing in extra daytime calories may reduce night feeds but will not necessarily eliminate night wakings. If your baby wakes but is not hungry, the issue is settling back to sleep, not hunger.

Swaddling for Younger Babies

For babies in the first few months, swaddling can genuinely help. The mechanism is straightforward: young infants have a strong startle reflex (the Moro reflex) that causes their arms to fling out and can jolt them awake. Swaddling suppresses that reflex. Research has shown that swaddled infants arouse less frequently and sleep longer overall.¹⁴ More specifically, swaddling decreases startles and full arousals during quiet sleep and reduces the progression from startle to full waking.¹⁵ A systematic review and narrative synthesis found that swaddling increased quiet sleep duration and reduced the number of sleep-state changes, particularly in babies who had not been swaddled before.¹⁶

Swaddling needs to stop once your baby starts showing signs of rolling over, typically around two to four months. After that point, being swaddled with arms restricted becomes a suffocation risk. Transitional products like sleep sacks with arms free can help bridge the gap. The startle reflex usually fades around the same time, so the main benefit of swaddling diminishes naturally.

Why Sleep Falls Apart at Certain Ages

You have probably heard of the “four-month sleep regression.” The concept is real, though “regression” is a misnomer. What is actually happening is developmental progress that temporarily disrupts sleep. Research has documented that sleep disruptions cluster around the onset of new motor milestones. A study of pulling-to-stand, typically achieved in the second half of the first year, found that among babies who reached this milestone early (by eight months), the achievement was directly linked in time to a period of disrupted sleep.¹⁷

Broader research has confirmed this link across multiple milestones. Disruptions to sleep have been found around the onset of first crawling steps, first walking steps, walking mastery, and even language milestones like babbling, new word use, and object labeling.¹⁸ A time-series analysis confirmed that changes in sleep patterns track with changing expertise for motor milestones, though the specific relationship varies by baby and by sleep parameter.¹⁹

The practical takeaway is that if your baby was sleeping well and suddenly is not, take stock of what new physical or cognitive skill is emerging. These disruptions tend to be temporary, lasting days to a couple of weeks. The worst thing you can do during a developmental sleep disruption is abandon every habit that was working. Keep the routine, stay consistent, and ride it out. The sleep will consolidate again once the new skill is better integrated.

Where Your Baby Sleeps

This is where the science gets genuinely tricky, because two well-supported recommendations pull in somewhat different directions. The American Academy of Pediatrics recommends room-sharing (baby in your room, on a separate sleep surface) for at least the first six months, citing evidence that this arrangement may reduce the risk of SIDS by as much as 50 percent.²⁰

At the same time, a study from the INSIGHT trial found that babies who moved to their own room before four months had better sleep consolidation at four months, with a longest sleep stretch roughly 46 minutes longer than room-sharers. By nine months, early independent sleepers were getting 40 more minutes of total nighttime sleep. The gap persisted even at 30 months, with babies who were sleeping independently by nine months still getting more than 45 extra minutes per night. Room-sharers also had four times the odds of transitioning to bed-sharing during the night.²¹

The AAP’s safety guidance is built on evidence about SIDS risk reduction, and safety outweighs sleep optimization. But the INSIGHT study highlights a real trade-off that parents should be aware of. After six months, when the SIDS risk drops substantially, moving your baby to their own room may improve sleep for both of you. Before that, the safest approach per current guidelines is to keep the baby in your room on a separate firm surface, alone and on their back. If the noise of a baby sleeping three feet away is waking everyone up, white noise machines and strategic crib placement can help without changing rooms.

Cultural Expectations and Sleep Norms

Much of the advice around getting babies to sleep through the night reflects Western, and specifically North American, norms. A large cross-cultural study spanning 17 countries found enormous variation in infant sleep patterns. Bedtimes ranged from 7:27 p.m. in New Zealand to 10:17 p.m. in Hong Kong. Total sleep time ranged from about 11.6 hours per day in Japan to 13.3 hours in New Zealand. Bed-sharing rates varied from under 6 percent in New Zealand to over 83 percent in Vietnam.²² The percentage of parents who perceived their child as having a sleep problem ranged from 11 percent in Thailand to 76 percent in China, which tells you that “sleep problem” is partly a cultural construct shaped by expectations.

Co-sleeping is a common and culturally accepted practice in many parts of the world, though in Western countries it often carries stigma and is discouraged by medical guidelines due to SIDS concerns.²³ From an evolutionary perspective, some researchers have proposed that frequent night waking in breastfed infants may itself be adaptive. One hypothesis suggests that waking to suckle extends the mother’s period of lactational infertility, delaying the arrival of a sibling and thus improving the infant’s own survival odds.²⁴ Whether or not that evolutionary framing holds up, it is a useful reminder that night waking in infancy is not a disorder. It is normal mammalian behavior that you are managing, not a pathology you are treating.

When to Talk to Your Pediatrician

Most infant sleep struggles are behavioral and developmental, but some have a medical component. Obstructive sleep apnea can occur even in infants, and it is worth being aware of the signs. Factors that increase the risk of airway obstruction in babies include conditions affecting the jaw, tongue, or airway like laryngomalacia (a floppy airway) or micrognathia (an underdeveloped jaw), as well as more common issues like gastroesophageal reflux and chronic nasal congestion.²⁵ If your baby snores loudly, pauses in breathing during sleep, has consistently restless or noisy sleep despite all the behavioral interventions you have tried, or seems excessively sleepy during the day, bring it up with your doctor. These are not problems a bedtime routine will fix.

Ear infections, teething pain, and food intolerances can also drive temporary increases in night waking that look like behavioral sleep problems but resolve once the underlying cause is treated. If your baby’s sleep takes a sudden and dramatic turn for the worse and no developmental milestone or schedule change explains it, a medical checkup is a reasonable next step before doubling down on behavioral strategies.