# What is the 4-month sleep regression? | Clever Mum > Around 3–5 months, babies’ sleep permanently reorganises into adult-like cycles with more light sleep — so a baby who "slept through" starts waking again. It’s * [ Home ](/) * › [ Mum Answers ](/answers) * › What is the 4-month sleep regression? Sleep # What is the 4-month sleep regression? Quick answer — What is the 4-month sleep regression? Around 3–5 months, babies’ sleep permanently reorganises into adult-like cycles with more light sleep — so a baby who "slept through" starts waking again. It’s development, not a setback, and it doesn’t always pass quickly on its own. Consistent wind-downs, full feeds in the day and practising settling in the cot all help. ## What's actually happening Newborns drop straight into deep sleep and spend most of their sleep there. Around 3–5 months, that architecture permanently matures into the adult pattern: cycles of roughly 45–60 minutes moving through light and deep stages, with brief natural wakings between cycles. A baby who needs feeding, rocking or a dummy to fall asleep will often call for that same help at every cycle boundary — which is why the waking suddenly multiplies. ## Why "regression" is the wrong word Nothing has gone backwards — this is a one-way upgrade to mature sleep. That also means it doesn't simply "pass" like a growth spurt: the new cycles are permanent, and what changes is your baby learning to link them. ## What helps * **A consistent, boring wind-down** at every bedtime, so sleep cues do some of the work. * **Full feeds in daylight hours** to gently shift calories away from the night. * **Practising cot-settling** — drowsy-but-awake some of the time, without turning it into a battle. * **Holding your safer-sleep line**: back to sleep, clear cot, room-share to 6 months, whatever the night throws at you. Our [sleep training methods comparison](/baby/sleep-regressions-and-sleep-training-methods-compared) covers the structured options if you choose that route later. **Go deeper:** [Newborn sleep guide](/baby/newborn-sleep-guide-first-12-weeks/) **Buying guide:** [Best white noise machines](/best/best-white-noise-machines-uk/) ## More Sleep questions * [When should my baby move into their own room?](/answers/when-move-baby-own-room/) * [What tog sleeping bag does my baby need?](/answers/what-tog-sleeping-bag/) * [What is the safest way for my baby to sleep?](/answers/safest-way-for-baby-to-sleep/) * [When should I stop swaddling my baby?](/answers/when-to-stop-swaddling/) * [Why does my baby only nap for 30–45 minutes?](/answers/why-does-my-baby-only-nap-30-minutes/) [Browse every question we answer →](/answers/) Health answers describe NHS guidance and are not medical advice — for anything urgent, call 111 (or 999 in an emergency). Spotted something out of date? Email [editors@clevermum.co.uk](mailto:editors@clevermum.co.uk).