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Sleep Regression by Age

Pick an age on the timeline and this shows what is genuinely changing in a baby around then, what tends to happen to the nights, and how long parents usually report it running. It also says the part the rest of the internet leaves out: none of the publishers this page stands on uses the word regression at all.

No account, no email, and nothing you type is sent anywhere.

Pick an age · the six the internet argues about
yours 4m 6m 8–10m 12m 18m 24m
9 months

Eight to ten months is one of the named windows, and on the evidence it is the busiest of the six. Most weeks in a baby’s life are not one of these, which is worth remembering when a bad fortnight arrives at eleven months and does not match anything on the chart.

Eight to ten months

8–10 months
What is actually developing

The busiest window on this page. Crawling is a skill usually mastered between seven and ten months, sitting without support is established by about eight, and pulling up to standing follows almost immediately — often before she has worked out how to get back down. Some babies never crawl at all and scoot or slither instead, which the AAP treats as unremarkable.

Quoted from the American Academy of Pediatrics’ own milestone pages, linked below. Milestones are guidelines with wide variation, not dates.
What tends to happen to the nights

Two things collide. There is a new physical skill that has to be practised, and it will be practised at two in the morning; and separation anxiety begins in the second half of the first year, which the AAP says can cause many nights with disrupted sleep and can run for several months.

Described rather than measured. Where a source covers it — separation anxiety, night waking being ordinary — it is named in the text and linked below.
The part nobody else prints

This is the window most likely to be genuinely hard, and also the one most likely to be blamed on something you did. Neither the crawling nor the separation anxiety is a consequence of how the baby has been settled. There is no published duration for any of it.

This site’s own reading of what the sources do and do not support.
two to six weeks is what parents commonly report, and it is unsourced. No publisher this site may cite recognises the category, let alone times it — so treat any duration you read anywhere, including this one, as an estimate somebody made up and everybody copied.

Two patterns, not one timetable

The largest study of the question followed more than 1,200 infants at 6, 15, 24 and 36 months and did not find a single developmental curve that everybody was on. It found two, and they stayed apart:

Woke about one night a week, throughout66%
Woke every night at six months34%
Down to two nights a week by fifteen months and one night a week by two years — a slope, not a switch, and never the same slope as the other group.

Neither group is the broken one. If your baby is in the second, no chart of regression ages was ever going to describe her nights, because the chart is drawn from the first.

What this is. A timeline of a word that no health body uses. “Sleep regression” is not a clinical term, none of the publishers this page stands on recognises the category, and not one of them publishes the famous list of months or a duration for any of it. That list is folklore rather than a finding — useful folklore, assembled by parents out of the ages when babies commonly learn something new, but folklore, and this page would rather say so than pretend a chart is a measurement. What they do publish is when rolling, sitting, crawling, standing and words usually arrive, and that separation anxiety disrupts nights from the second half of the first year — so this page is built from that and says which column is which. Every age band on it is an estimate with a wide range around it.

What it refuses to do. It will not tell you how long a bad fortnight will last, because nobody has measured it. It will not tell you that every baby has these, because the evidence points the other way. It attaches no month to sleeping through the night — the American Academy of Pediatrics is plain that a good sleeper at this age is a baby who wakes frequently and gets herself back down, and that sleeping undisturbed for prolonged periods at this age is not the goal. There is no AI here and nothing on this page can see your baby.

Safe sleep first, especially in a hard fortnight. Every sleep happens the same way however broken the night gets: on their back, on a firm flat surface, in a cot clear of blankets, pillows, bumpers and soft toys, in your room for at least the first six months. Nothing weighted goes on or over a sleeping baby, and a baby who has started rolling still goes down on her back. If your baby is very hard to settle, unusually sleepy, feeding poorly, losing weight, or something simply feels wrong to you, that is a call to your pediatrician or health visitor rather than a phase to wait out — and none of this is medical advice.

How this is worked out

  1. You pick one of the six ages the search results argue about, or move the age control and let the page find the nearest one. Everything is read in this browser and nothing is sent anywhere.
  2. The development column is quoted, not invented. Rolling, and the rocking and kicking that lead to it, usually appear around five months; sitting without support arrives around eight; crawling is usually mastered between seven and ten months; pulling to standing follows; first words around a year and roughly one new word a week between eighteen months and two. Those are the American Academy of Pediatrics' own milestone pages, and they are guidelines with wide variation rather than dates.
  3. The nights column is the part with the least behind it, and it is labelled that way. What is published is that separation anxiety disrupts sleep from the second half of the first year and can last several months, usually fading around the second birthday — and that frequent night waking is developmentally appropriate rather than a problem to be fixed.
  4. The durations are honest to the point of being unsatisfying. No publisher this site may cite says a regression lasts two weeks, or six, or anything at all, because none of them recognises the category. Where a duration is shown it is described as what parents commonly report, and is marked as unsourced on the page itself.
  5. The counterweight to the whole timeline is one study of more than 1,200 infants followed to three years, which found two lasting patterns rather than one: about two thirds woke their mothers roughly one night a week throughout, and about a third woke every night at six months, still twice a week at fifteen months and once a week at two years. Neither group is the broken one.
Questions

The short answers

The list you will meet everywhere is four months, six months, eight to ten months, twelve months, eighteen months and two years. It is worth knowing where that list comes from: it is not from the NHS, the American Academy of Pediatrics, the NIH or any published paper — none of them uses the term. It is a folk taxonomy assembled from the ages at which babies commonly learn something new, and it is genuinely useful as a map of when nights tend to get harder. It is not a clinical finding and there is no test for it.
Nobody who publishes anything this page is allowed to cite has ever measured it, so any number you read has been made up somewhere and copied since. What parents commonly report is two to six weeks, and the timeline above says so while marking it as unsourced. What is measurable is the underlying developmental change, and those take as long as they take: crawling is usually mastered somewhere across a three-month window, not on a date.
No, and the ones who do not are not luckier or better parented. What is real at around four months is that a baby's sleep stops looking newborn: sleep cycles become more regular from about that age, which changes how easily a baby resurfaces between them. Whether that shows up as a fortnight of five-times-a-night or as barely anything is not something anybody can predict from the outside, and a baby who sails through it has not skipped a stage.
Waking is the normal state. The American Academy of Pediatrics is blunt about it: at this age a good sleeper is a child who wakes frequently but can get back to sleep, not one who sleeps ten hours unbroken, and sleeping undisturbed for prolonged periods at this age is not what you should be aiming for. What deserves a call to your pediatrician or health visitor is not the waking itself but the things around it — poor feeding, no weight gain, a baby who cannot be settled at all, a cry that does not sound like her usual one, or any change that simply frightens you. Nothing on this page is medical advice and it cannot examine anybody.
Hold the parts of the day that are cheap to hold and let go of the rest. Keep the same order of events at bedtime, keep the room and the routine boring, offer more daytime practice at whatever new skill is keeping her up, and expect to do more of the settling than you did a month ago. Do not use a hard fortnight as the moment to drop a nap. And keep every sleep safe however broken the night gets: on their back, on a firm flat surface, in a cot clear of blankets, pillows and toys.

Where this comes from

  1. American Academy of Pediatrics (HealthyChildren.org) (2013). Sleeping Through the Night. https://www.healthychildren.org/English/ages-stages/baby/sleep/Pages/Sleeping-Through-the-Night.aspx
  2. Developmental Psychology (PubMed) (2012). Patterns of developmental change in infants' nighttime sleep awakenings from 6 through 36 months of age. https://pubmed.ncbi.nlm.nih.gov/22448981/
  3. American Academy of Pediatrics (HealthyChildren.org) (2024). Getting Your Baby to Sleep. https://www.healthychildren.org/English/ages-stages/baby/sleep/Pages/getting-your-baby-to-sleep.aspx
  4. American Academy of Pediatrics (HealthyChildren.org) (2021). Movement Milestones: Babies 4 to 7 Months. https://www.healthychildren.org/English/ages-stages/baby/Pages/Movement-4-to-7-Months.aspx
  5. American Academy of Pediatrics (HealthyChildren.org) (2021). Movement Milestones: Babies 8 to 12 Months. https://www.healthychildren.org/English/ages-stages/baby/Pages/Movement-8-to-12-Months.aspx
  6. American Academy of Pediatrics (HealthyChildren.org) (2022). Separation Anxiety and Sleeping. https://www.healthychildren.org/English/healthy-living/sleep/Pages/separation-anxiety-and-sleeping.aspx
  7. American Academy of Pediatrics (HealthyChildren.org) (2012). Developmental Milestones During the First 2 Years. https://www.healthychildren.org/English/ages-stages/toddler/Pages/Milestones-During-The-First-2-Years.aspx
  8. American Academy of Pediatrics (HealthyChildren.org) (2022). How to Keep Your Sleeping Baby Safe: AAP Policy Explained. https://www.healthychildren.org/English/ages-stages/baby/sleep/Pages/A-Parents-Guide-to-Safe-Sleep.aspx
  9. NHS (2025). Reduce the risk of sudden infant death syndrome (SIDS). https://www.nhs.uk/baby/caring-for-a-newborn/reduce-the-risk-of-sudden-infant-death-syndrome/

Every link above was opened and read when this page was last updated. Snuggle is not affiliated with any of these organisations and none of them has reviewed this page. Nothing here is medical advice.

Go deeper

The reading behind this page

Sleep, by age · 10 min read

Sleep Regression at 4 Months

Sleep cycles arrive at about four months and they do not go away again — which is why this one is a maturation rather than a regression, and why it behaves differently from every age after it.

Read it Sleep, by age · 9 min read

Sleep Regression at 6 Months

Six months is where the evidence is best in this whole subject — and what it shows is that a baby who wakes in the night and settles again is doing something ordinary, not something wrong.

Read it Sleep, by age · 9 min read

8 Month Sleep Regression

Sitting, crawling and pulling to standing all arrive in the same few weeks — and a baby who can get herself up but not back down will work on it at one in the morning.

Read it Sleep, by age · 9 min read

Sleep Regression at 12 Months

A first birthday changes the paperwork, not the child — what is genuinely developing at a year, and why the morning nap she is fighting is usually not one she has finished with.

Read it Sleep, by age · 9 min read

Sleep Regression at 18 Months

The age where the bedtime objection comes with a vocabulary — what is genuinely developing at eighteen months, and the nap that has quietly slid an hour later than it started.

Read it Sleep, by age · 9 min read

Sleep Regression in a 2 Year Old

At two the trouble is mental rather than motor: imagination arrives, and the first fears arrive with it — alongside the bed, the toilet and the nap she refuses but still needs.

Read it
Next door

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Age plus the signs you are actually seeing, and an honest read on which nap transition is near — including the answer that it is not one yet.

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Baby Sleep Schedule Generator

Your baby's age and this morning's wake-up, drawn as a day: naps and bedtime as windows, widening through the afternoon the way real days do.

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White Noise Player

White, pink and brown noise made in your browser with a fade-out timer — and the measurement study that decides where the machine should sit and how loud it should be.

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The app this site is for

Snuggle does this with your baby’s own pattern.

This page works from an age band, because an age band is all a web page knows about you. Snuggle starts from the same bands and then blends them with what your baby actually did today — how long she lasted, when she went down, how the last nap ran — and shows on the face of the ring how sure it is. Early estimates say they are early.

It logs sleep, feeds, nappies and growth in one tap on a dim red screen, and every caregiver in the household is on the same timeline in their own account. The arithmetic runs on the phone, on your baby’s own history. There are no AI features in it.

In development for iPhone and Android. Not released yet — when it is, it will be on this site.

What Snuggle is