The 4-month change, and why it isn't a setback
Around four months, sleep stops being newborn sleep. It gets lighter, more cycled, more like yours — and the nights that had started to settle come apart. That isn’t a regression. It’s a rebuild.
6 min read
For the first few months, babies drop straight into deep sleep and stay there. Then the architecture changes: sleep splits into cycles, and between cycles there’s a surfacing — a brief, almost-awake moment. Adults have these too. You turn over and never remember it.
A baby who has always fallen asleep one particular way will surface and look for that way again. If it was motion, they want motion. If it was a feed, they want the feed. Nothing has broken. They’ve simply started noticing the gap.
What to hold steady
The instinct is to change everything at once — earlier bedtime, longer naps, a new settling method, a different room. Change one thing and give it four nights. Two nights tells you almost nothing; a week is longer than most parents can hold their nerve.
Keep the last hour identical. Same order, same rooms, same light. Predictability is doing more work than any single technique.
Protect the first stretch. The longest sleep of the night usually sits right after bedtime. Guard it, even if the rest of the night is messy.
Move bedtime earlier, not later. An overtired baby surfaces more, not less. Fifteen minutes earlier is often the whole fix.
Decide who takes which wake. Before the night starts, while you can both still think.
Nothing has gone backwards. The thing that used to work stopped being invisible.
How long it usually takes
Most families see the nights steady over two to four weeks, and it rarely happens in a straight line — a good stretch, then two rough nights, then a better week. Some babies take longer. Nobody can put a date on it, and anyone who does is guessing.
If feeding is painful, if there’s a lot of arching or refusing, or if something just feels off to you, that’s a conversation with your health visitor or paediatrician rather than a sleep problem to schedule around.
Want this worked out for your baby instead?
The quiz takes three minutes and asks about your nights, not just their age.
Take the 3-min quiz →General guidance, not medical advice. Your paediatrician's advice takes precedence.