Why sleep changes now
Around four months, sleep cycles mature. That can make your baby’s sleep look lighter and more interrupted.
What to focus on
Protect daytime sleep, keep bedtime age-appropriate and avoid making too many changes at once.
Stay realistic
A “perfect schedule” is not the goal. A calmer pattern is.
Important: baby sleep varies enormously. Avoid one-size-fits-all promises, and always prioritise feeding, growth and safe sleep advice.
Safer sleep reminder. For babies, use a firm, flat sleep surface and follow the latest safer sleep advice from the NHS and The Lullaby Trust.
Want to know what is disturbing your baby's sleep?
The Petit Nuage sleep quiz looks at age, naps, night waking and settling habits to show you what to focus on first.
Take the 2-minute quiz →Frequently asked questions
How many naps should a 4 month old have?
It varies, but several naps are still normal.
Why did sleep suddenly get worse?
This age is well known for temporary sleep disruption.
Should I change everything now?
No. Start with small, high-impact changes.
Reference sources: NHS baby sleep guidance · The Lullaby Trust safer sleep information. Last updated: 24 September 2026.