- A sleep regression is a few rough weeks when sleep that was going fine suddenly isn't. It usually comes with a new skill or a step in development, and it passes.
- The common ages: about 4 months, 6 months, 8–10 months, 12 months, 18 months and 2 years.
- Only the 4-month one rests on solid research: sleep matures into adult-like cycles between about 2 and 6 months. The later ones are milestones and life changes landing at once.
- Night waking is normal all through the first year: in one study of 388 babies, 28–57% of 6- and 12-month-olds didn't sleep 6–8 hours straight, with no effect on their development.
- Born early? Count from the due date (corrected age) until 2 years. The calendar does it for you.
Sleep regression ages: the chart
| Age (corrected) | What's going on | How long | Evidence |
|---|---|---|---|
| first 6–8 weeks | newborn crying runs high, then drops after 8–9 weeks (not a sleep regression) | eases by 10–12 weeks | well documented |
| about 4 months (3–5) | sleep matures into adult-like cycles, for good; brief wake-ups between cycles | rough patch often 2–6 weeks | well documented |
| about 6 months | 3 → 2 naps, rolling and sitting, first teeth, solids | often 1–3 weeks | loosely documented |
| 8–10 months | crawling, pulling up to stand, separation anxiety | often 2–6 weeks | some research |
| about 12 months | walking, the first nap strike | often 1–4 weeks | some research |
| about 18 months | independence, separation anxiety, molars | often 2–6 weeks | loosely documented |
| about 2 years | new fears, toddler bed, potty, a new sibling | often 1–4 weeks | loosely documented |
“How long” is what pediatric sleep advice commonly reports, not something studies have measured. Every baby runs a little ahead or behind, and plenty sail through some of these without anyone noticing.
How the calendar works
Each regression has a window in weeks of age: the 4-month one, for example, from 14 to 20 weeks. The calendar puts those windows on your baby's dates and marks each one as behind you, likely now, next or later. For a baby born more than 3 weeks early, add the due date and the windows move to corrected age, the way pediatricians count development until 2 years.
Every entry carries an evidence label. Well documented means sleep or crying research shows the change itself. Some research means the milestone is real and studies link it to worse sleep for a while, but the evidence is thin. Loosely documented means no study shows a sleep change at that age; it's a name for several things that tend to happen together. “Add to calendar” saves the windows that are still ahead as all-day events with a reminder a week before, so the next rough patch doesn't take you by surprise.
What a sleep regression is, and isn't
“Sleep regression” isn't a medical term. You won't find it in pediatric guidelines or in sleep research; it's what parents and sleep coaches call the stretch when a baby who slept well starts waking again. Most of these stretches are really progress. The best documented is the change around 4 months: sleep that was two simple states at birth becomes adult-like cycles of light and deep sleep, and the AAP notes that babies don't have regular sleep cycles until about 4 months. Recordings of infant sleep show the biggest changes between 2 and 6 months, and diaries show the fastest consolidation in the first 4 months.
The later “regressions” line up with motor milestones. In studies that tracked sleep at home, babies' sleep got more broken when they started to crawl, when early achievers learned to pull up to stand, and while they were learning to walk; the disruption was temporary. Separation anxiety, which the AAP says usually peaks between 10 and 18 months, adds bedtime protests and night calls.
What a regression is not: a sign that you've done something wrong, or that your baby has “forgotten” how to sleep. And it isn't an illness. If the waking comes with a fever, pain, breathing trouble, poor feeding or fewer wet diapers, call your pediatrician.
What helps, whatever the age
- A short, predictable bedtime routine. In a study of 405 families, a three-step nightly routine (bath, massage, quiet time) shortened the time to fall asleep and cut night waking within two weeks, and the mothers' mood improved too.
- Room to settle. In a survey of 5,006 families, babies whose parents encouraged self-soothing slept longer and in fewer pieces than babies who were actively helped to sleep. Putting your baby down drowsy but awake some of the time is a gentle way to practice.
- Practice new skills by day. Crawling, standing and walking get practiced in the crib when they're new. More floor time during the day takes some of the novelty out of the night.
- An early bedtime after a bad day. Short naps make babies tired sooner; the nap planner shows wake windows by age and re-plans the day when a nap goes short.
- Same safe sleep, every time. On the back, on a firm flat surface, in an empty crib or bassinet, even at 3 a.m. when anything that works is tempting.
Born early? Use corrected age
For a baby born more than about 3 weeks early, development, sleep included, runs from the due date rather than the birthday. Pediatricians use this corrected age until about 2 years. A baby born 6 weeks early is likely to hit the 4-month changes closer to 5½ months after birth. Tap “Born more than 3 weeks early?” in the calendar and add the due date; every window moves to match.
Frequently asked questions
What are the sleep regression ages?
The ages most often named are about 4 months, 6 months, 8–10 months, 12 months, 18 months and 2 years. Only the change around 4 months is backed by solid sleep research; the others match motor milestones, separation anxiety and big life changes. Count from the due date for a baby born early.
When is the next sleep regression?
Enter your baby's birth date in the calendar above and it shows which windows are behind you, which is likely happening now and when the next one starts, in about how many weeks. You can add the windows still ahead to your phone's calendar.
How long does a sleep regression last?
Most rough patches are said to last 1 to 6 weeks, often 2 to 4. Nobody has measured this carefully, and the 4-month change itself is permanent: what passes is the rough adjustment to it, not the new way of sleeping.
Is there a 2 year sleep regression?
Many parents see one: stalling at bedtime, calling out, early waking. Research doesn't show a sleep change at 2 years. What usually sits behind it is new fears and imagination, a move to a toddler bed, potty training or a new sibling. A predictable bedtime and keeping the crib while it still works help most.
Should I plan by leaps or Wonder Weeks?
The calendar doesn't, on purpose. The leaps idea goes back to a 1993 study of 15 mothers and their babies, which found difficult periods at set ages. It's one small study, and leaps aren't part of pediatric guidance such as the AAP's. Development is real; the exact weeks are not something to plan around.
Does sleep training stop a sleep regression?
No method makes a regression skip your baby. What research does support is a consistent bedtime routine and giving babies the chance to settle on their own some of the time; both are linked to longer, less broken sleep. If you're thinking about a formal method, talk it over with your pediatrician.
Is it a regression, or is my baby sick?
A regression looks like a well, happy baby who wakes more. Call your pediatrician if the waking comes with a fever, pain, ear pulling with a cold, breathing trouble, vomiting, poor feeding or fewer wet diapers, or if your gut says something's off.
Does teething cause sleep regressions?
Less than people think. In a study that followed 125 babies through 475 new teeth, symptoms showed up only in an 8-day window around each tooth: 4 days before, the day itself and 3 days after. Wakefulness rose in that window; sleep disturbance overall didn't. Weeks of bad nights are rarely just teeth.
Sources
- HealthyChildren.org (AAP): Getting Your Baby to Sleep: babies don't have regular sleep cycles until about 4 months
- Jenni O.G., Borbély A.A., Achermann P., Development of the nocturnal sleep electroencephalogram in human infants, Am J Physiol Regul Integr Comp Physiol 2004: largest changes between 2 and 6 months
- Henderson J.M.T. et al., Sleeping through the night: the consolidation of self-regulated sleep across the first year of life, Pediatrics 2010
- Wolke D., Bilgin A., Samara M., Fussing and crying durations and prevalence of colic in infants: a systematic review and meta-analysis, J Pediatr 2017
- Pennestri M.H. et al., Uninterrupted infant sleep, development, and maternal mood, Pediatrics 2018
- Scher A., Crawling in and out of sleep, Infant Child Dev 2005
- Atun-Einy O., Scher A., Sleep disruption and motor development: does pulling-to-stand impact sleep–wake regulation? Infant Behav Dev 2016
- DeMasi A. et al., Infant motor development predicts the dynamics of movement during sleep, Infancy 2023
- HealthyChildren.org (AAP): Emotional and Social Development, 8 to 12 Months: separation anxiety usually peaks between 10 and 18 months
- Mindell J.A. et al., A nightly bedtime routine: impact on sleep in young children and maternal mood, Sleep 2009
- Sadeh A. et al., Sleep and sleep ecology in the first 3 years: a web-based study, J Sleep Res 2009
- Macknin M.L. et al., Symptoms associated with infant teething: a prospective study, Pediatrics 2000
- van de Rijt-Plooij H.H.C., Plooij F.X., Distinct periods of mother–infant conflict in normal development, J Child Psychol Psychiatry 1993 (the origin of the “leaps”)
- HealthyChildren.org (AAP): Corrected Age for Preemies
- Moon R.Y. et al., Sleep-Related Infant Deaths: Updated 2022 Recommendations for Reducing Infant Deaths in the Sleep Environment, Pediatrics 2022
Spotted a mistake or an outdated figure? Write to [email protected].