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Sleep Regression Ages: Every Regression From 4 Months to 2 Years

By Tiny Moments · Updated November 2026 · 8-minute read

Baby sleep regressions happen at predictable ages — around 4 months, 8–10 months, 12 months, 18 months and 2 years — and most last 2 to 6 weeks. Each one is driven by a different developmental leap, which is why the same tricks don't work at every age. Here's the full map, plus a what-to-do playbook for each one.

A sleep regression is a stretch when a baby who was sleeping reasonably well suddenly wakes more at night, fights naps, or resists bedtime. It is not a step backwards: it is the visible side of the brain learning something new. Some night waking is normal at every age — what changes during a regression is how often it happens, not whether your baby can sleep at all.

The sleep regression ages at a glance

What to do at each age

4 months — the big one

This is the only regression that is structural: your baby's sleep cycles permanently change from newborn-style sleep into adult-style cycles with light and deep stages. Between cycles they now wake up properly — and if they need help falling asleep, they need that same help every time they wake. It usually lasts 2–6 weeks, and it is the most consistent regression because every baby's sleep matures. Protect the wake windows (about 1.5–2.5 hours at this age), keep bedtime identical every night, and resist changing everything at once. We wrote a full guide to this one: 4-Month Sleep Regression: Signs, How Long It Lasts & Survival Tips.

8–10 months — the mover

Crawling, pulling to stand and cruising arrive together with separation anxiety — your baby now understands you exist when you leave the room, and objects. Expect standing practice in the crib at 2 a.m. and protests at naps and bedtime. Give the new skills plenty of daytime practice so the crib isn't the only rehearsal stage, keep the routine the same, and offer brief reassurance at night rather than starting new sleep associations you don't want to keep. It usually resolves in 2–6 weeks, once the skill stabilises.

12 months — the nap tease

First steps and first words make this one, but the real trap is the nap: your one-year-old starts refusing the second nap, and it looks like they are ready for one nap. Most still need two. Dropping too early is what stretches this regression out. Keep two naps a little longer, recheck the wake windows, and treat the refusal as a phase rather than a schedule change. This is usually the shortest regression — 1–4 weeks.

18 months — the boundary tester

A language explosion, new independence and molars collide, and bedtime becomes one of the first limits your toddler tests. Expect bedtime resistance, night wakings tied to new fears, and nap strikes. Many parents call this the hardest stage. The answer is boring on purpose: the same short bedtime sequence every night, calm responses, and no new negotiations at 10 p.m. It usually takes 2–6 weeks, and the longest tail is often boundary-related rather than sleep-related.

2 years — the imagination years

Nightmares, fear of the dark, stalling tactics and nap resistance — plus big life changes like a new sibling, a toddler bed or potty training. A dim night light, a short predictable routine and clear, kind limits help most toddlers feel safe enough to settle. Protect bedtime even when the nap shortens, and keep reassurance brief rather than turning it into a long nightly negotiation. Most 2-year regressions settle in 2–6 weeks.

Is it a regression — or something else?

Teething, illness, hunger and growth spurts can all look like a regression. A quick check before you assume:

• Sudden change + new skills? A baby who was sleeping well and is suddenly waking, while also rolling, crawling, walking or talking more — that pattern points to a regression.
• Fever, rash, feeding much less, or seems unwell? That is not a regression. Talk to your pediatrician.
• Gradual change over weeks? More likely a schedule problem — wake windows that no longer fit, or a nap transition that is due. Check the wake window chart by age first.
• Broken sleep beyond 6–8 weeks? Check the other causes: hunger, reflux, discomfort, illness, or a nap transition. A regression that never ends is usually something else wearing a regression's clothes.

Three rules that help at every age

1. Don't change everything at once

A regression is a bad time to drop a nap, move rooms, change the bedtime routine and start sleep training in the same week. Pick one change if you must, or change nothing at all. Steady days are what help sleep rebuild fastest once the new skill settles.

2. Decide the night plan at 2 p.m., not 2 a.m.

At 2 a.m. you will not make good decisions, so make them in daylight: pause briefly before responding (some wakings are just cycle transitions), check the basics (hungry? wet? too hot or cold?), settle in the least stimulating way that works, and keep lights low and talking to a minimum. Whatever you choose, do it the same way all night.

3. Look after the adults too

Broken sleep for weeks wears anyone down. Split the night into shifts where you can, nap when the baby naps at least once a day, and say yes to any offered help. If you feel persistently low, anxious or unable to cope, talk to your doctor — that matters as much as your baby's sleep.

Sources & further reading: KidyGrow — Baby Sleep Regression Ages: Chart, How Long Each One Lasts · Pippy — Baby Sleep Regression Ages: When They Happen and What to Do · KidsHealth (Nemours) — All About Sleep