Your baby was sleeping beautifully. Then, seemingly overnight, the naps got short, bedtime got hard, and the nights filled with wake-ups that no amount of rocking seems to fix. If this is you, take a breath: this is almost certainly the 4-month sleep regression, and it is one of the most normal — and most exhausting — milestones in the first year.
Here is the part nobody tells you, and it's strangely reassuring: it isn't really a regression at all. It's a progression.
What the 4-month regression actually is
Around 3–5 months, your baby's sleep permanently matures from newborn sleep into more adult-like sleep cycles. They now move through lighter and deeper stages and fully surface between cycles — roughly every 45 minutes. A newborn would have drifted straight back down. Your 4-month-old briefly wakes, notices the world, and needs help getting back to sleep.
Because it's a permanent change in how your baby sleeps, the new skill — linking sleep cycles — is here to stay. That's why we say it's a progression: your baby is growing up. They just need a couple of weeks to find their feet.
Signs it's the 4-month regression
- Naps suddenly shrink to 30–45 minutes (one sleep cycle)
- More frequent night wake-ups, often every couple of hours
- Bedtime becomes a battle when it used to be easy
- Your baby seems hungrier, and may be working on rolling
- Fussier, clingier days alongside the broken nights
How long does it last?
For most babies, the rough patch lasts around 2–4 weeks while they adjust. The underlying change is permanent, but the disruption settles — especially once a gentle, consistent rhythm helps your baby practise resettling.
What genuinely helps (the gentle version)
You don't need to "sleep train" your way through this. A few calm, consistent shifts make the biggest difference:
- Watch wake windows. At this age, ~2–2.5 hours awake is typical. Overtiredness makes the regression dramatically worse — see our wake windows by age guide.
- A short, predictable wind-down. The same few cues each time (dim lights, nappy, sleeping bag, a quiet feed or song) tell the maturing brain what comes next.
- A dark, cool, boring sleep space. White or pink noise can soften that between-cycle surfacing.
- Offer a chance to resettle. When your baby stirs, pause a moment before rushing in — sometimes they find their own way back down. Respond if they need you; you're always the safe base.
- Protect daytime sleep and full feeds. A well-rested, well-fed baby copes far better at night.
- Look after you. Tag-team the nights, lower the bar on everything else, and remember this is temporary.
When it might not be the regression
A few short nights are normal; weeks of escalating chaos with no settling can point elsewhere — teething, a growth spurt, illness, silent reflux, or a wake-window/schedule that's drifted off. If feeds and weight are a worry, or something just feels wrong, always check in with your health visitor or GP. For reflux and colic specifically, our colic and reflux support guide may help.
How OBubba helps you through it
This is exactly the moment OBubba was built for. Its sleep engine watches your real logs and flags when a regression or developmental leap is likely — so a brutal fortnight reads as "this is normal, and temporary," not "I'm doing something wrong." It also keeps your nap and bedtime timing dialled in while the regression plays out, and offers gentle, data-led settling guidance — like a sleep consultant quietly reading your nights. See our baby sleep consultant app page for how it works.
The 4-month regression is hard, but it's a sign your baby is exactly where they should be. Keep it gentle, keep it consistent, and you'll both come out the other side.
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