Swaddle
Usual age
3-5 months
Often lasts
Weeks
Is it a problem?
Normal
Signs of the 4 month sleep regression
- More night wakings, sometimes every 1-2 hours
- Short naps of 30-45 minutes (one sleep cycle)
- Harder to settle at bedtime
- More fussing when put down
Why it happens
Newborns spend a lot of their sleep in "active" sleep and drop quickly into deep sleep. Between about 3 and 5 months, sleep reorganizes into the cycle pattern older children and adults have, with lighter stages between cycles. Every cycle ends with a brief arousal.
Adults barely notice these arousals. A baby who always falls asleep while feeding, rocking or being held may now wake fully at the end of a cycle and need the same help to fall back asleep. That is why this "regression" is better thought of as a progression: the change in sleep architecture is permanent, even if the rough patch is not.
It often lands at the same time as rolling, more alertness and a growing interest in the world, which can make naps harder too.
What helps
- Use age-right wake windows. At 4 months that is usually about 1.5 to 2 hours. Overtired babies wake more. Try our wake window calculator.
- Bring bedtime earlier on days with short naps, even by 30 minutes.
- Darken the room for naps and nights, and use steady white noise at a safe volume.
- Practice falling asleep in the crib for one sleep a day, often bedtime. Put your baby down drowsy and see what happens. Read drowsy but awake.
- Pause before going in at night. A minute or two lets you hear whether your baby is waking or just stirring between cycles.
- Stop swaddling once your baby shows signs of rolling, and move to an arms-out sleep sack.
- Keep feeding when they are hungry. Growth and a busier day can mean more night feeds for a while. That is not a habit, it is a baby.
How long does it last?
Many families say the roughest part lasts 2 to 6 weeks. The change in sleep cycles itself is permanent, so the goal is not to get back to newborn sleep but to help your baby learn to link the new cycles.
When to call your pediatrician
A sleep regression is a normal phase. Call your pediatrician if poor sleep comes with fever, breathing that seems hard or noisy, snoring with pauses, vomiting, a rash, ear pulling with fussiness, fewer wet diapers or poor feeding, or if your baby just seems unwell or unlike themselves. Trust your instincts.
Want the whole day mapped out? See the 4 month old sleep schedule.