- When: around the first birthday, roughly 11–13 months, with a second wave for some babies around 15 months. Born early? Count from the due date.
- What: first steps, separation anxiety near its peak, and often a few days of refusing the second nap.
- How long: often 1–4 weeks.
- The one thing to do: keep offering two naps. A few days of refusal is a strike; most toddlers move to one nap during the second year, by about 18 months.
When does the 12 month sleep regression start?
The calendar above puts it between about 50 and 58 weeks of age, so from a couple of weeks before the first birthday to a month or so after. That's a range, not a date: it follows walking and the first nap strike, and both arrive at different times for different babies. For a baby born more than 3 weeks early, the window runs from the due date, the same corrected age pediatricians use until 2 years.
The 1 year sleep regression
“1 year sleep regression” and “12 month sleep regression” are two names for the same rough patch. Nothing changes in the brain on the birthday itself; what changes is a baby who is about to walk, has opinions, and has noticed that the second nap is optional.
The 15 month sleep regression
Some toddlers have a second wave around 15 months. By then many are walking well and some are ready to give up the morning nap, which is why the 15-month version is mostly about naps: a few weeks of short or refused naps while the day reshapes itself around one nap after lunch.
What's really going on
Three things tend to land at once around the first birthday, and each one shows up at night.
Walking. In a 2023 study that tracked 78 babies' sleep at home with movement sensors, picking up a new motor skill brought a temporary rise in night waking and movement during sleep, and babies who were in the middle of learning to walk slept worse than was typical for their age. Standing, cruising along the crib rail and taking steps are all new, and a baby practices what's new, including at 2 a.m.
Separation anxiety. The AAP says separation anxiety usually peaks between 10 and 18 months and fades in the second half of the second year. A 1-year-old knows you exist when you leave the room, and may wake up looking for you in the middle of the night.
The nap strike. Many 1-year-olds refuse the second nap for a few days. It looks like a sign they're ready for one nap. Usually it isn't yet.
Nap strike or a real move to one nap?
| Nap strike | Ready for one nap | |
|---|---|---|
| Age | often around 12 months | during the second year; most by 18 months |
| How long it's been | a few days | the second nap refused for 1–2 weeks running |
| The rest of the day | cranky late afternoon, falls apart by bedtime | copes well until bedtime on one nap |
| The morning nap | still happens at the usual time | keeps creeping later on its own |
| What to do | keep offering two naps; an earlier bedtime on refusal days | move the single nap toward noon in 15-minute steps every few days |
The nap planner's wake windows by age show both options from 12 months and tell you when a day only works with one nap.
Signs of the 12 month sleep regression
- The second nap refused, or turned into 20 minutes of standing and chatting.
- Standing or cruising in the crib instead of lying down, and crying because getting back down is still hard.
- Protest at bedtime, especially when you leave the room.
- Waking at night after weeks of sleeping through, often calling for a parent.
Night waking at this age isn't a problem in itself. In a study of 388 babies, 28–57% of 6- and 12-month-olds didn't sleep 6 or 8 hours straight, depending on the cut-off, and sleeping through the night had no link with their mental or motor development.
How long does the 12 month sleep regression last?
Often 1 to 4 weeks. That figure comes from everyday pediatric sleep advice, not from studies, and it varies a lot: the walking-related waking in research was temporary, and a nap strike often settles within a week or two if the second nap stays on offer. If sleep is still broken a month later, look at the day: too little daytime sleep and a late bedtime are the usual culprits.
What helps
- Don't drop the second nap over a short strike. Keep offering it in a dark, quiet room. If it doesn't happen, a little quiet time in the crib still helps, and an earlier bedtime that day covers the gap. Total sleep at 1–2 years is 11–14 hours in 24 hours, naps included.
- Walking practice by day. Plenty of time on the floor, pushing a walker toy, cruising along the sofa. The more ordinary standing and walking become during the day, the less tempting they are at night.
- Practice getting down. Help your toddler bend their knees and sit down from standing, again and again, so the crib stops being a trap.
- The same short routine every night. In a study of families with babies and toddlers, a three-step nightly routine shortened the time to fall asleep and cut night waking within a couple of weeks.
- Calm, boring, predictable answers at night. Go in, lay them down, say the same short phrase, leave. Babies whose parents encourage settling on their own tend to sleep longer and in fewer pieces.
What the evidence says
Some research “12 month sleep regression” isn't a term you'll find in research. What studies do show is that new motor skills, walking included, go with a temporary rise in night waking, and that separation anxiety peaks in the same months. The nap strike is a pattern from everyday experience; there are no studies of it. Most toddlers move to one nap by 18 months.
What's next
For many toddlers, the next bumpy stretch comes around 18 months, with bedtime battles, molars and a lot of “no!”. Before that, the move from two naps to one is the big change; plan it with the nap planner. The sleep regression calendar puts every window on your own dates.
Frequently asked questions
When is the 12 month sleep regression?
Around the first birthday: roughly 11 to 13 months of age, counted from the due date for a baby born more than 3 weeks early. It tends to arrive with walking and a first nap strike, so it shifts with your baby's own timing.
How long does the 12 month sleep regression last?
Often 1 to 4 weeks. Research shows the extra night waking around walking is temporary, and a nap strike usually settles within a week or two if the second nap stays on offer.
Is my 1 year old ready for one nap?
Probably not yet. Most children move to one nap during the second year, by about 18 months. Wait until the second nap has been refused for 1–2 weeks running, not just a few days, and your toddler copes well until bedtime on one nap.
Is there a 15 month sleep regression?
Many parents see a second wave around 15 months. It's mostly about naps: some toddlers are ready to drop the morning nap then, and the switch brings a few weeks of short or refused naps and earlier bedtimes.
Why does my 1 year old stand in the crib and cry?
Standing is new and exciting, and getting back down is harder than getting up. Practice sitting down from standing during the day; at night, lay them down calmly and briefly, the same way every time.
Should my 1 year old be sleeping through the night?
Many aren't, and that's normal. In one study, between 28% and 57% of 6- and 12-month-olds didn't sleep 6–8 hours straight, with no link to their development. If waking comes with a fever, pain or poor eating, call your pediatrician.
Sources
- DeMasi A., Horger M.N., Scher A., Berger S.E., Infant motor development predicts the dynamics of movement during sleep, Infancy 2023: new motor skills bring a temporary rise in night waking; infants learning to walk slept worse
- HealthyChildren.org (AAP): Emotional and Social Development, 8 to 12 Months: separation anxiety usually peaks between 10 and 18 months
- Pennestri M.H. et al., Uninterrupted infant sleep, development, and maternal mood, Pediatrics 2018
- Nemours KidsHealth: Naps: most toddlers drop to one nap by 18 months
- HealthyChildren.org (AAP): Healthy Sleep Habits: How Many Hours Does Your Child Need?: 11–14 hours at 1–2 years, naps included
- 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
Spotted a mistake or an outdated figure? Write to [email protected].