4 month sleep regression

When
Usually between 3 and 5 months
How long
Often 2–6 weeks, but it is a permanent change in how sleep works rather than a phase that fully reverses
Typical wake window
1.5–2.25 h
Typical naps
3–4

Why it happens

  • Sleep architecture matures: babies start cycling through light, deep and REM stages like adults do, with a brief near-waking between cycles.
  • Babies who are used to falling asleep with help (feeding, rocking, a pacifier) may need that help again at each cycle change.
  • Rolling and more awareness of surroundings arrive at the same time.

Common signs

  • More night wakings after a stretch of longer sleep
  • Naps shrink to 30–45 minutes (one sleep cycle)
  • More fussing at bedtime

Try it: how sleep cycles change around 4 months

A simplified picture of a few hours of night sleep. Toggle between the two ages.

Brief wakingREMLightDeep

Now sleep starts light, dives into deep sleep, and comes back up to a near-waking at the end of each cycle (amber dots). A baby who fell asleep being fed or rocked may call out to get that help back each time.

What helps

  • Keep a consistent, short bedtime routine.
  • Give your baby some chances to fall asleep in the crib drowsy but awake.
  • Use an earlier bedtime on short-nap days.
  • Stop swaddling once your baby shows signs of rolling (AAP).
  • Keep night care calm and dim.

Call your pediatrician if your baby has a fever, seems unwell, is feeding poorly, snores loudly or pauses in breathing, or if the disruption lasts more than a few weeks.

A steady daytime rhythm makes rough nights easier to ride out. Here's a typical day for this age:

4 month old schedule

Naps per day
Plan the day from
Wake windows
1 h 50 min → 2 h → 2 h 10 min → 2 h 20 min
Daytime sleep
3 h 30 min
Night in bed
12 h 10 min
Typical 24 h total
12–16 h (incl. naps)

Your day at a glance

12a3a6a9a12p3p6p9p
Night sleepNapsAwake
  1. 7:00amWake up for the day
  2. 8:50am–10:05amNap 1 · 1 h 15 min
  3. 12:05pm–1:35pmNap 2 · 1 h 30 min
  4. 3:45pm–4:30pmNap 3 · 45 min
  5. 6:50pmBedtime · start routine 6:20pm

A flexible guide built from typical ranges. Watch your baby's sleepy cues and shift by 15–30 minutes as needed. Every sleep: on the back, in a clear, flat crib (AAP).

Questions

When does the 4 month sleep regression start?

Usually between 3 and 5 months.

How long does the 4 month sleep regression last?

Often 2–6 weeks, but it is a permanent change in how sleep works rather than a phase that fully reverses.

Does every baby have a 4 month sleep regression?

Every baby goes through the change in sleep cycles, but not every family notices a big disruption. Babies who already fall asleep independently often sail through.

Should I sleep train during the 4 month regression?

Many pediatric sources suggest waiting until at least 4–6 months and until your baby is feeding well. Ask your pediatrician whether your baby still needs night feeds.

Other guides: 8 month sleep regression · 18 month sleep regression