When do babies sleep through the night? The phrase means 5 to 6 hours, not eight, and that changes the answer

So if you are reading this at 3:12 a.m. with a five month old who woke at 11:40 and again just now, hold on to that second sentence before you read anything else. The thing you think you are failing at may not be the thing anyone published. Below: what the phrase actually means, the ages with the organization attached to each number, why the fourth month often makes it worse, what to do in the next twenty minutes, when night feeds are still doing a job, and the short list of night waking that is a reason to call.

What "sleeping through the night" actually means

Start with the definition, because almost every argument about baby sleep is really an argument about this word.

Nemours KidsHealth writes that some babies start to sleep "through the night", meaning 5 to 6 hours at a time, by 2 to 3 months of age, and that some do not. Nemours KidsHealth Five hours. Not 7 p.m. to 7 a.m. A baby who goes down at 8 p.m., wakes at 1:30 a.m. and feeds is, by the published definition, sleeping through the night.

The AAP puts the same point from the other direction, on a page it titles Sleeping Through the Night (last updated 2013). At this age, it writes, a good sleeper is a child who wakes up frequently but can get himself back to sleep, and is not a child who sleeps without waking for 10 hours at night. Frequent waking is developmentally appropriate, and sleeping undisturbed for prolonged periods at this age is not healthy. AAP HealthyChildren The same organization says elsewhere that frequent night waking is developmentally normal in the early months and that long unbroken sleep is not expected from a newborn. AAP HealthyChildren

Read those two together and the question quietly changes shape. The measure is not how long the block is. It is whether a baby who surfaces can settle again, and whether the settling is getting a little easier month by month.

The NHS adds the part no table can: some babies sleep much more than others, some in long periods and some in short bursts. NHS Your neighbour's ten week old and yours are both inside the published range.

The ages, with the organization attached to every number

Every figure below is quoted from the body that published it. We have not averaged anything, and we have not filled a gap with a guess.

Sources for the table, in order of first use: CDC totals CDC; MedlinePlus awake windows and the 4 month, 9 month and nap figures MedlinePlus (NIH); AAP newborn stretches AAP HealthyChildren; Nemours on 2 to 3 months Nemours KidsHealth; NHS on 3 to 6 and 6 to 12 months NHS. Naps sit inside those totals, and MedlinePlus puts the first year at 1 to 4 naps a day, each 30 minutes to 2 hours.

Two things the table is not. It is not a schedule, and no row is a target your baby can miss. The CDC's newborn row, unlike the 4 to 12 month row, does not carry the words "including naps", CDC which is a small reminder that even the published numbers are not cut to the same pattern.

When do babies start sleeping through the night, in one paragraph

If you want the single sentence: a first 5 to 6 hour stretch shows up for some babies between 2 and 3 months and for others much later, per Nemours KidsHealth; Nemours KidsHealth a stretch that looks like an adult night, 8 hours or more, is a 4 month possibility rather than a 4 month expectation, per MedlinePlus, whose word is "might"; MedlinePlus (NIH) and the age at which most infants can go 8 to 10 hours without a night feed is around 9 months, if not sooner, again per MedlinePlus. MedlinePlus (NIH) Between those milestones the NHS is honest about the spread: 5 to 8 hours or longer at 3 to 6 months, for some babies, but not all. NHS

Why the fourth month often gets harder, not easier

This is the part that surprises people, and it is the reason a parent who was doing fine in week nine arrives here in week eighteen.

Babies usually do not develop regular sleep cycles until about 4 months of age, per AAP HealthyChildren. AAP HealthyChildren Before that there is no settled architecture to break. When the cycles arrive, a baby starts surfacing between them, which is exactly what MedlinePlus means when it writes that infants will still wake during the night and that over time they learn to self-soothe and fall back asleep. MedlinePlus (NIH) The learning is the slow part.

So a baby who was doing five hour stretches at ten weeks can come apart at eighteen weeks and be entirely on schedule. Nothing was lost. The system underneath changed. MedlinePlus's advice for this stage is one sentence long: put your baby in bed drowsy, before they are deeply asleep, which helps them learn to fall asleep on their own. MedlinePlus (NIH) Our 4 month sleep regression article walks through the whole mechanism.

There is a second dip later, and it has a different cause. The NHS writes that separation anxiety and fear of strangers is common between the ages of 6 months and 3 years, that it is a normal part of development which children usually grow out of, and that it is a sign a baby now realises they are a separate person from you. NHS A nine month old who slept through at seven months and does not now may be doing something a developmental page describes rather than something a sleep page does.

What to do at 3 a.m.

Nothing here installs a sleep cycle. These are the published habits, and they work on the margins over weeks, not tonight.

1. Keep the night boring. MedlinePlus: for night feedings, keep the room dark and quiet, leave the lights off, and keep the feeding brief and low-key rather than playtime. MedlinePlus (NIH) The AAP says the same thing about handling: try not to stimulate or wake babies when you feed or change them during the night, and if you speak, speak softly. AAP HealthyChildren
2. Change the nappy only if it needs changing. The NHS's night list is short: lights down low, voices quiet, put the baby down as soon as they have been fed and changed, no nappy change unless it is needed, no play. A baby gradually learns that night-time is for sleeping. NHS
3. Put them down on their back, in their own flat sleep space. Every sleep, naps and nighttime, per NICHD Safe to Sleep, which calls back sleeping the single most important thing you can do to lower the risk of SIDS. NICHD Safe to Sleep If you feed in your bed, the baby goes back to their own crib or bassinet before you settle down.
4. Keep the crib in your room. NICHD Safe to Sleep advises sharing a room, but not a bed, for at least the first 6 months, which also makes the night feed shorter because nobody crosses a hallway. NICHD Safe to Sleep The NHS gives the same 6 month advice for day and night sleep. NHS
5. From 4 months, hand back one small piece of the settle. Into bed drowsy rather than fully asleep, per MedlinePlus. MedlinePlus (NIH) If it turns tonight into a fight, stop and try again next week. This is practice, not homework.
6. Work on the daytime instead. The AAP writes: make daytime playtime, keep babies awake longer during the day, and this helps babies sleep for longer periods during the night. AAP HealthyChildren The NHS adds that a simple soothing bedtime routine may help a baby settle, and suggests a bath, night clothes and a fresh nappy, bed, and a story. NHS

If the wake is at the front of the night and looks more like refusing bed than waking from it, that is a different problem with a different fix, and it is the subject of our article on a baby who fights sleep rather than this one.

When night feeds are still doing a job

Here is the tension nobody on page one of the search results resolves. If "through the night" is 5 to 6 hours, and a newborn is not supposed to go long without eating, which is it?

Both, in order. Nemours KidsHealth writes that newborns who sleep for longer stretches should be awakened to feed, that you wake your baby every 3 to 4 hours to eat until they show good weight gain, which usually happens within the first couple of weeks, and that after that it is fine to let your baby sleep for longer periods at night. Nemours KidsHealth Weight gain comes first, and the long stretch is allowed to follow it.

The rest of the published picture:

• Newborns wake often to eat, roughly every 2 to 3 hours breastfeeding and about every 3 to 4 hours bottle-feeding, per Nemours KidsHealth. Nemours KidsHealth
• MedlinePlus writes that a newborn should not go more than 4 hours at night without feeding, 4 to 5 hours if formula feeding, and that it is fine to wake them to eat. MedlinePlus (NIH) Our newborn feeding schedule article has the full pattern by age.
• By 9 months, if not sooner, most infants can sleep at least 8 to 10 hours without needing a nighttime feeding, per MedlinePlus. MedlinePlus (NIH)
• For some babies aged 6 months to a year, night feeds may no longer be necessary, per the NHS, which in the same breath says teething discomfort or hunger may still wake some babies during the night. NHS

Notice what none of those four says. None of them names a week to stop night feeds, and neither will we. The published language is "may no longer be necessary" and "most infants can", which is a description of a spread, not a date on a calendar. The person who can put a date on it for your baby is your pediatrician, who knows the weight chart.

What does not make a baby sleep longer

• Solid food. The NHS is direct: starting solid foods will not make your baby any more likely to sleep through the night, though sometimes a little extra milk will help until they are ready for solids. NHS
• Goodnight milk. The NHS writes that this type of formula is not suitable for babies under 6 months, is not needed, and that there is no evidence babies settle better or sleep longer after having it. NHS
• Keeping a baby up so they crash. The AAP's published version of the daytime idea is longer awake time and active play during the day, not a skipped nap before bed. AAP HealthyChildren
• A comparison with another baby. The NHS says some babies sleep much more than others, some in long periods and some in short bursts. NHS Two healthy babies born the same week can be five hours apart.
• A purchase at 2 a.m. No device installs a sleep cycle. If a page is telling you your baby needs something tonight, close the tab.

When night waking is a reason to call

Most night waking is the ordinary kind described above. The signals below are different, and each one carries the name of the organization that publishes it. None of these thresholds is ours.

• The AAP's own check on night waking. Healthy, growing babies usually do not need to be awakened to feed, and the AAP (Sleeping Through the Night, 2013) says to check with your pediatrician about nighttime awakening if your baby is not doing the following: growing and gaining weight steadily; feeding well 8 to 12 times a day breastfeeding, or 5 to 8 times a day bottle-feeding; urinating normally with at least 4 wet diapers a day; and having at least 3 normal bowel movements a day. AAP HealthyChildren This is a call, not an emergency, and it is the one item on this list that is specifically about waking.
• Fever in a baby 3 months or younger. The AAP writes (Fever and Your Baby, 2025) that a rectal temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher means calling your pediatrician immediately. AAP HealthyChildren A baby who is suddenly waking far more than usual and is warm gets a temperature check before anything else.
• Fewer wet diapers, or a baby who is hard to rouse. The AAP (Signs of Dehydration in Infants and Children, 2019) lists fewer than six wet diapers a day among the signs of mild to moderate dehydration in an infant, and says to notify the pediatrician immediately if any of the signs develop. AAP HealthyChildren Being excessively sleepy and very fussy sit on its list of severe signs. AAP HealthyChildren A baby who sleeps through a feed they would normally wake for is worth a second look, not a celebration.
• Call 911. Seattle Children's Hospital (handout PE1736, 2024) publishes four things that mean call 911 now for an infant: they stop breathing for 15 seconds or longer; they have severe difficulty breathing; they have blue-tinged skin around the lips, fingernails and gums, which may not be visible on darker skin tones; and you are unable to wake your baby. Seattle Children's PE1736 Cleveland Clinic (Periodic Breathing in Newborns, 2025) draws its own line at a pause longer than 10 seconds, and we print both numbers rather than averaging them. Cleveland Clinic

And the rule that outranks the whole list: if your baby seems unwell to you tonight, that is a call to your pediatrician at any hour, and the person who answers would rather hear from you.