What is the 4-month sleep regression and how do I cope?

Somewhere between 3 and 5 months, a lot of parents hit the same wall. The baby who had finally started sleeping in longer stretches is suddenly waking every hour, fighting naps and generally unsettled. The internet calls it the 4-month sleep regression, and if you're in the thick of it, I'm sorry. It's genuinely hard.

The good news, sort of, is that nothing has gone wrong. Nothing you did caused it and nothing you could have done would have prevented it. For the newborn baseline before this shift, see how much sleep a newborn needs.

Why is my 4 month old suddenly waking every hour?

Here's the odd part: your baby's sleep isn't going backwards. It's maturing.

Newborns drop almost straight into deep sleep. That's why a two-week-old can conk out mid-feed, get transferred to the cot, have a nappy vaguely adjusted, and stay asleep through the lot.

Around 4 months, the brain reorganises sleep into adult-style cycles. There's more light sleep, and the baby now surfaces briefly between cycles, the way you and I do. We roll over and drift off again without ever really noticing. Your baby hasn't learned that trick yet. So they surface, realise something feels different from when they fell asleep, and call for you.

Waking between cycles is the new normal. The skill they need to build is falling back asleep on their own, and building it takes a while.

How does baby sleep change at 4 months?

The unsettled phase typically eases within 2 to 6 weeks. The new sleep-cycle structure, though, is permanent. This is how your baby sleeps from now on. What changes is how well they cope with it.

How do I cope with the 4-month sleep regression?

There's no fix, but there are things that help:

• Keep a consistent, boring wind-down routine. Same order, same dim room, same dull sequence every night. Predictability is soothing when everything in their head is changing.
• Watch wake windows rather than the clock. An overtired baby fights the new cycles even harder, so let their cues, not the schedule, decide when the nap happens.
• Try putting baby down drowsy but awake. If they fall asleep in the cot, the cot is what they find when they surface between cycles, which is far less alarming than waking somewhere different. Some babies take to this quickly, others need time. Either is normal.
• Keep night interactions dim and dull. Feed, change if you must, back to the cot. No lights, no chat, no fun. You're the most boring version of yourself at 3am, on purpose.
• Tag-team where you can. If there are two of you, split the night so each of you gets one protected stretch. A soother run at 2am is easier when you got to sleep until midnight.
• Lower every other expectation for a few weeks. The washing can wait. Dinner can be toast. This phase passes.

Do the safe sleep rules change during the regression?

Whatever you try during this phase, the safe sleep rules stay the same: baby on their back, in a cot, in your room for at least the first six months. That's the HSE guidance and it holds through regressions, growth spurts and everything else. For the full rules, togs and the rolling question, see the safe sleep guide, and for what normal looks like on the far side, when babies sleep through the night.

How do I know if it's the regression or my baby is sick?

The regression makes babies wakeful and cranky. It doesn't make them ill. If your baby also has a fever, is refusing feeds or just seems unwell to you, treat that as illness, not sleep development, and talk to your PHN or GP. You know your baby. Trust the feeling that something's off.

How do I know if my baby's sleep is getting better?

Compare this week's nights with last week's rather than judging by how you feel at 3am: the unsettled phase typically eases within 2 to 6 weeks, and the sign it is passing is the slow return of longer stretches. Most parents can't tell from memory, because every night feels the same shade of awful. Lullagram's sleep logs show the actual pattern, the shorter cycles appearing and then the longer stretches coming back, and the Sleep Window feature keeps suggesting realistic nap timing as the windows stretch, so you're not working off a schedule that suited the baby they were a month ago. It is free to try on Android, iPhone and web.

The HSE has more on baby sleep if you want the official guidance alongside the practical.