Is the 4-month regression permanent?

The change is permanent — your baby's sleep cycles mature — but the disruption usually settles within 2 to 6 weeks as your baby learns to connect the new cycles.

What if my baby doesn't have a regression?

Some babies sail through. If nights and naps stay stable, there is nothing wrong and nothing to fix.

Do regressions happen at exactly these weeks?

No. The windows shown are averages. A two-week wobble in either direction is normal.

Should I sleep train during a regression?

Most consultants suggest waiting until the regression settles. Adding a new expectation on top of a developmental leap usually backfires.

How long does an 8-month regression last?

Typically 2 to 6 weeks. Consistency with your usual sleep approach shortens it.

Is there a 6-month regression?

Six months is not a formally recognized regression, but many babies transition from 3 to 2 naps around then, which can look like one.

My toddler is regressing outside these windows. Why?

Common culprits include teething, illness, travel, a big life change (new sibling, new bed, new care setting), or fear development around age 2 to 3.

What helps during any regression?

Protect sleep pressure with age-appropriate wake windows, keep your bedtime routine boringly consistent, and lean into extra co-regulation and reassurance during the wobble.

Sleep regression timeline by birth date

Sleep regressions are predictable developmental leaps that briefly disrupt sleep — most fall around 4 months, 8 to 10 months, 12 months, 18 months, and 2 years. Enter your child's birth date and this timeline will show which regressions are behind you, which one is active right now, and which is next.

Your child's birth date

Nothing is stored. The date lives in the URL so you can bookmark or share this timeline.

Pick your child's birth date to see which regressions are behind you and which are next.

4-month sleep shift
Weeks 14–20
The permanent maturation of sleep cycles. Not a phase — a new normal.
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8–10 month regression
Weeks 34–44
Separation anxiety plus new mobility (crawling, pulling to stand) disrupts naps and nights.
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12-month regression
Weeks 50–56
Often mistaken for a 2-to-1 nap transition. Usually settles in 1 to 2 weeks.
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18-month regression
Weeks 76–82
Growing independence, language explosion, and molar teething all collide.
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2-year regression
Weeks 100–108
New fears, boundary-testing, and a possible last-nap wobble.
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What this tool can't see: your child's specific temperament, history, and what you have already tried.

Get help through this regression

How this works

The regressions plotted here are drawn from developmental research on sleep architecture (the 4-month shift), object permanence and separation anxiety (8 to 10 months), gross-motor leaps, language explosions, and the well-documented independence stages at 18 months and 2 years.

A "regression" is a misleading word — sleep isn't going backwards. Your child's brain is doing something new, and sleep is briefly the cost.

The date ranges are averages. A regression can start a couple of weeks early or late and still be normal.