The sleep regression ages chart
A sleep regression is a period — usually two to six weeks — when a baby or toddler who had been sleeping reasonably well suddenly starts waking more at night, fighting naps, or resisting bedtime. They cluster around predictable ages because they follow the big leaps in how a child's brain and body develop.
| Age | What's driving it | Typical length | Guide |
|---|---|---|---|
| ~4 months | Sleep cycles permanently mature into adult-like stages — the biggest, most consistent regression | 2–6 weeks | 4-month guide |
| ~6 months | Rolling, early teething, growth spurts | 1–3 weeks | 6-month guide |
| ~8–10 months | Crawling, pulling to stand, separation anxiety, 3→2 nap transition | 2–6 weeks | 8-month guide |
| ~12 months | First steps, nap refusal (most still need two naps) | 1–2 weeks | Guide coming |
| ~15 months | Walking, first words, 2→1 nap transition | 1–3 weeks | Guide coming |
| ~18 months | Independence, molars, separation anxiety — many parents' hardest stage | 2–6 weeks | 18-month guide |
| ~2 years | Nightmares and new fears, nap resistance, big life transitions | 1–6 weeks | 2-year guide |
| ~3 years | Imagination and bedtime fears, stalling, dropping the nap | 2–6 weeks | Guide coming |
Some families also notice a rocky patch around 8 weeks, when evening fussiness peaks, and around 2.5 years — both are common, though less consistently reported than the stages in the chart.
What is a sleep regression, really?
"Regression" is a slightly unfair word. Your child isn't going backwards — their brain is going forwards so fast that sleep temporarily pays the price. Most regressions line up with either a biological change (the 4-month restructuring of sleep cycles), a motor milestone (rolling, crawling, standing, walking — babies literally practice in their cribs), or a cognitive-emotional leap (object permanence, separation anxiety, imagination and fears).
That's why the answer to "when will this end?" is usually "when the leap is done." A baby who has just mastered pulling to stand stops treating the crib as a gym. A toddler who has settled into a new daycare routine stops fighting bedtime. The regression is the turbulence, not the destination.
How to survive any regression: the five basics
- Hold the routine. A predictable, boring bedtime sequence is your anchor. Children find repetition deeply reassuring precisely when their world is changing.
- Protect daytime sleep. An overtired baby sleeps worse at night, not better. Watch wake windows before you change anything else.
- Give daytime practice. Lots of floor time to rehearse the new skill (rolling, crawling, standing) means less rehearsal at 2 a.m.
- Comfort without building new habits you don't want. Extra reassurance is right during a regression — just be intentional about what you repeat every night, because it can outlast the regression.
- Mark the calendar. Most regressions resolve within two to six weeks. Knowing it is a phase changes how it feels at 3 a.m.
Where is your baby on the map?
Enter your baby's birthdate and the Sleep Regression Calculator builds their personal timeline — which stages are behind you, whether you're likely in one right now, and what's coming next (with dates).
Frequently asked questions
What ages do sleep regressions happen?
The most commonly reported ages are around 4 months, 6 months, 8–10 months, 12 months, 15 months, 18 months, 2 years and 3 years. The 4-month regression is the most consistent because it reflects a permanent change in how babies cycle through sleep.
How long does a sleep regression last?
Typically two to six weeks. Milestone-driven regressions often settle once the skill is mastered; the 4-month change is permanent, but the disruption still eases as babies learn to link their new sleep cycles. Full breakdown: how long regressions last, by age.
Is the 4-month sleep regression real?
Yes — it's the one with the clearest biology. Around 3–5 months, babies move from newborn sleep patterns to adult-like cycles with lighter stages, which means more chances to fully wake between cycles. Our 4-month guide covers it in depth.
Do all babies go through every regression?
No. Plenty of babies breeze through some stages, and some hit rough patches at ages that appear on no chart. These windows describe common patterns, not a schedule your baby signed up to.
Can you prevent a sleep regression?
Not really — they're driven by development you wouldn't want to stop. What you can do is soften the landing: consistent routine, age-appropriate wake windows, daytime skill practice, and a calm, dark sleep space.
When should I talk to a doctor?
See your pediatrician or health visitor if poor sleep comes with snoring or pauses in breathing, poor weight gain, fewer wet diapers, fever or unusual lethargy — or if disruption lasts well beyond six weeks without improving. Trust your instincts; that's what checkups are for.