The 4-month sleep regression: what it is and how to get through it

Your baby was sleeping in lovely long stretches, and then — around 4 months — it all fell apart. Frequent wakes, short naps, fighting sleep. This is the famous 4-month sleep regression, and the good news is it's a sign of normal development.

What's actually happening

It's less a "regression" and more a permanent progression. Around 4 months your baby's sleep matures from newborn sleep into a more adult-like structure with distinct sleep cycles (~40–50 minutes). At the end of each cycle they briefly surface — and now they notice, and need help linking to the next one.

How long does it last?

Usually 2–6 weeks. It's a phase, not a new baseline. It passes.

How to get through it

• Watch wake windows. At this age, roughly 75–120 minutes awake. Overtiredness makes everything worse.
• Full feeds in the day so hunger isn't driving the night wakes.
• A short, consistent wind-down before sleep — same order every time — so your baby's brain learns "sleep is coming."
• Give a beat before responding to a night wake; sometimes they're just resurfacing between cycles and will resettle.
• A dark room and white noise help mask the transitions between cycles.

What not to do

Don't overhaul everything at once out of exhaustion. Pick one or two changes, give them several days, and keep the day's rhythm steady. Consistency is what actually helps sleep cycles knit back together.

When to check in with a professional

If wakes are paired with feeding refusal, illness, or you're worried about your baby's weight or wellbeing, talk to your health visitor or pediatrician — this article is general guidance, not medical advice.

Tracking naps and wakes during the regression helps you see when it's easing (stretches lengthening, naps consolidating) instead of just feeling stuck in the fog. Ziggy makes that trend obvious at a glance.