4 Month Sleep Regression
The 4 month sleep regression usually starts between 3 and 5 months, when a baby's sleep cycles mature into a more adult-like pattern with lighter stages. Babies begin waking briefly between cycles, so night waking and 30–45 minute naps often appear almost overnight. The toughest part tends to last 2 to 6 weeks.
- Usually starts
- 3–5 months
- Typically lasts
- 2–6 weeks
- Main cause
- Sleep cycles mature
Reviewed by Pediatric sleep consultant (TBC) · Updated 2026-09-25
Check today's nap times
Next nap
8:45 am
after 1 h 45 min awake · typical 1¾–2½ hours
See the whole day
- 7:00 am Morning wake-up
- 8:45 am Nap 1 · until 10:05 am
- 12:05 pm Nap 2 · until 1:25 pm
- 3:40 pm Nap 3 · until 4:20 pm
- 6:50 pm Bedtime
Get a reminder before 8:45 am. The Wake Windows app pings you when the window is closing and re-plans the day when naps run short.
Why the 4 month sleep regression happens
- Sleep architecture changes permanently: babies now cycle through light and deep sleep roughly every 45 minutes at nap time and 1–2 hours at night.
- At each brief waking, a baby looks for the conditions they fell asleep with, such as being fed, rocked or held.
- Babies become more aware of their surroundings, which makes them easier to wake and harder to settle in busy places.
- Rolling often starts around the same time, adding practice sessions in the crib.
Signs of the 4 month sleep regression
- More night wakings, sometimes every 1–2 hours, after a period of longer stretches.
- Naps shrinking to 30–45 minutes, one sleep cycle.
- Harder time falling asleep at bedtime, with more fussing.
- Needing more help (feeding, rocking) to get back to sleep.
If your baby also has a fever, is feeding much less, or seems unwell, it is more likely illness than a regression. Check with your pediatrician.
What helps
- Keep wake windows age-appropriate, around 1¾ to 2½ hours at 4 months, so your baby is tired but not overtired.
- Use a dark room and steady white noise for every sleep to reduce the chance of waking between cycles.
- Practise putting your baby down drowsy at bedtime, when sleep pressure is highest and success is most likely.
- Move bedtime earlier, as early as 6:30 pm, on days with short naps.
- Stop swaddling once your baby shows signs of rolling, per AAP safe-sleep guidance.
- Stay consistent for at least a week before judging whether a change is working.
Sample day at 4 months
4 month old schedule that helps
Overtiredness makes any regression harder. At 4 months, wake windows of 1¾–2½ hours and 3–4 naps a day are typical. Here is a sample day for a 7 am wake-up:
- 7:00 am Morning wake-up
- 8:45 am Nap 1 · until 10:05 am
- 12:05 pm Nap 2 · until 1:25 pm
- 3:40 pm Nap 3 · until 4:20 pm
- 6:50 pm Bedtime
4 Month Sleep Regression questions
When does the 4 month sleep regression start?
Most often between 3 and 5 months. Some babies show signs as early as 12 weeks.
How long does the 4 month sleep regression last?
The most disruptive part typically lasts 2 to 6 weeks. The change in sleep cycles is permanent, so sleep improves as babies learn to link cycles rather than returning to how it was before.
Can you prevent the 4 month sleep regression?
Not completely, because it is a developmental change. A steady routine, sensible wake windows and some practice falling asleep in the crib make it easier.
Should I sleep train during the 4 month regression?
The AAP notes that some families start gentle sleep training from around 4–6 months. Check with your pediatrician first, and choose an approach that suits your family.