The 4‑month sleep regression: what’s actually happening

Why sleep suddenly changes

Around three to four months, your baby’s sleep matures. Instead of dropping straight into deep sleep, they start cycling through lighter and deeper stages the way adults do — and every light stage is a new chance to wake up fully.

It isn’t a step backward. It’s a developmental leap, and for most families it settles within two to six weeks.

What helps

• Keep a short, predictable bedtime routine: bath, feed, book, bed.

• Put your baby down drowsy but awake some of the time, so they practice falling asleep on their own.

• Watch for sleepy cues — rubbing eyes, staring off — and start the routine before they’re overtired.

• Keep night feeds calm and dim. No screens, no play.

Safe sleep still comes first

Every sleep, every time: on the back, in their own crib or bassinet, on a firm, flat mattress with nothing else in it. Stop swaddling as soon as your baby shows signs of rolling.

When to call us

Call if your baby is feeding much less, has fewer wet diapers or a fever, or if the sleep changes come with pauses in breathing or noisy breathing. And call if you’re running on empty — tired parents are part of our care too.

This article is general information, not medical advice. If you’re worried about your child, call us — or 911 in an emergency.