Short version
Around four months, sleep architecture changes and the old rhythm may stop fitting. The fix is usually not one magic trick, but a better day structure.
What changes around four months
Wake windows stretch
The baby may need more awake time than before, but not so much that the day ends overtired.
Nap count changes
Many babies start moving from four naps toward three naps, which can make the whole day feel unstable.
Short naps matter
Several short naps can push bedtime late or create a very long final wake window.
Context beats guessing
Tracking recent sleep makes it easier to choose between another nap and an earlier bedtime.
What to do first
- Check the age-based wake window for four months.
- Look at the first wake-up and the first nap of the day.
- Protect bedtime if naps were short.
- Use the day planner as a baseline, then let the app adapt when the real day changes.
When to call a pediatrician
If there are feeding concerns, breathing concerns, fever, pain, poor weight gain, or any safety worry, treat it as a medical question. NapCoach is for routine and sleep organization, not diagnosis.