12 Month Sleep Regression: Why It Happens and What Helps

The 12 month sleep regression is a short dip in sleep around the first birthday, often between 11 and 13 months. It usually comes from first steps, a burst in language and a new wave of separation anxiety arriving together. With a steady routine, most families see it ease within 1 to 2 weeks.

Just as you reach the first birthday, night wakings return, naps turn into a battle and bedtime becomes a protest. Here is what is going on, and what helps.

What causes the 12 month sleep regression?

First steps

First steps often appear between 9 and 15 months. Studies that follow babies through new motor skills find more night waking around the time a big skill like crawling or walking first appears.^1,2 The brain is busy with the new movement, even at night.

A burst in language

Around 12 months many babies say their first words and start to understand simple instructions. That is a lot of new learning, and it can make sleep lighter for a while.

A new wave of separation anxiety

Separation anxiety is expected anywhere between about 8 and 24 months, and it often comes in waves.³ Around the first birthday your baby knows you exist when you leave, can protest loudly, and may even follow you. Bedtime is the longest separation of the day, so it is where this shows up most.

Lots of changes at once

Many families change several things around the first birthday: bottle to cup, a new daycare room, new foods. Each one can unsettle sleep, and several at once add up.

What are the signs of the 12 month sleep regression?

• More night wakings after a calmer stretch
• Fighting naps or taking much longer to fall asleep
• Crying or protesting at bedtime
• Early morning wakings
• More clinginess during the day
• Wanting to be held to fall asleep

Before you put it down to the regression, rule out illness and teething. First molars often arrive between 13 and 19 months and can be uncomfortable.⁴

How much sleep does a 12 month old need?

How long does the 12 month sleep regression last?

With consistency, most families see it ease within 1 to 2 weeks. A large study of bedtime routines found that the more consistently a routine was kept, the better babies and toddlers slept.⁵ When routines change a lot during the regression, the new habits often last longer than the regression itself.

Is it time to drop to one nap?

Usually not yet. The regression and readiness for one nap look alike from the outside. The difference is timing:

• The regression: nap refusal that is sudden and new, within the last 2 to 4 weeks.
• Ready for one nap: steady refusal for 4 to 6 weeks, even after adjusting wake windows.

If you are unsure, wait. Dropping to one nap too early often leads to an overtired baby and a regression that feels longer.

What helps during the 12 month sleep regression?

Keep the bedtime routine the same. 20 to 30 minutes, the same steps every night, ending in the crib. Consistency matters most when everything else feels off.⁵

Make awake time active. Floor play, walking practice and exploring help your baby use up energy and practice new skills by day, so there is less to process at night.

Play peekaboo and hide and seek. Short, playful separations during the day show your baby that you always come back.⁶

Space out big changes. If a change is in your control, like moving rooms or weaning, try to leave 2 to 3 weeks between them.

Is 12 months a good time to sleep train?

Many families consider it around now. Sleep training is not the same as cry it out, and there are many gentle methods. What fits depends on your family and your baby's temperament.

• If your baby already falls asleep on their own: you likely don't need a new plan. Stay consistent and give it a week or two.
• If you are thinking about starting: wait if your baby is unwell, a molar is coming through, or a big change happened in the last 2 to 3 weeks.
• If you start and your baby is very distressed for several nights: it is okay to pause. That is reading your baby, not giving up.

What comes next after 12 months?

Between 12 and 15 months, separation anxiety often comes in waves, picky eating may start and reactions get bigger. Many toddlers move from two naps to one between 14 and 18 months, and the 18 month sleep regression often follows.

Mellow Kids tells you before it happens. The app shows what's coming up for your child's age, with gentle steps for each phase.

FAQ

When does the 12 month sleep regression start?

It often appears between 11 and 13 months. Treat the age as a window rather than a set date.

How long does the 12 month sleep regression last?

Most families see it ease within 1 to 2 weeks with a steady routine and consistent responses at night.

Is my 1 year old ready for one nap?

Probably not yet. Most babies move to one nap between 14 and 18 months. Sudden nap refusal at 12 months is usually the regression.

Can teething cause sleep problems at 12 months?

Yes. First molars often arrive between 13 and 19 months and can disrupt sleep for a few days. If your baby seems in pain, talk to your pediatrician.

When should I talk to my pediatrician?

Reach out if your baby seems to be in pain, is unwell, or is getting much less sleep than usual over several days.

Get the free 12 Month Sleep Regression Survival Guide, with a sample day, more tips and a checklist for tonight.

Get the free guide

References

1. Scher A, Cohen D. Sleep as a mirror of developmental transitions in infancy: the case of crawling. Monographs of the Society for Research in Child Development. 2015;80(1):70–88. doi:10.1111/mono.12145
2. DeMasi A, Horger MN, Scher A, Berger SE. Infant motor development predicts the dynamics of movement during sleep. Infancy. 2023;28(2):367–387.
3. Merck Manual Professional Edition. Separation Anxiety Disorder. merckmanuals.com.
4. American Dental Association. Eruption Charts. MouthHealthy.org.
5. Mindell JA, Li AM, Sadeh A, Kwon R, Goh DYT. Bedtime routines for young children: a dose-dependent association with sleep outcomes. Sleep. 2015;38(5):717–722. doi:10.5665/sleep.4662
6. American Academy of Pediatrics. Separation Anxiety and Sleeping Trouble in Young Children. HealthyChildren.org.