Why it happens
Sleep cycles become more mature around this age. Babies may wake more clearly between cycles and need help linking them.
What helps most
Protect naps as much as possible, keep bedtime calm and age-appropriate, and focus on one gentle sleep change at a time.
How long it lasts
It varies. Some babies move through it quickly, others need more time and support.
Important: every baby's sleep is different. Avoid one-size-fits-all promises, and always put feeding, growth and safer sleep first.
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.
What's affecting your baby's sleep?
The Petit Nuage Sleep quiz considers your baby's age, naps, night waking and how they settle, helping you work out what to focus on first.
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Frequently asked questions
Is the 4 month regression real?
Yes, in the sense that sleep often changes around this stage.
Should I sleep train during it?
There is no need to rush. Start with timing and routines first.
Will it pass by itself?
Sometimes, but some patterns can persist without small adjustments.
Reference sources: NHS baby sleep guidance · The Lullaby Trust safer sleep information. Last updated: 28 October 2026.