4 month sleep regression — how long does it last?

The 4-Month Sleep Regression — You're Not Doing Anything Wrong 💙

In short: Yes, this sounds exactly like the 4-month sleep regression. It typically lasts 2-6 weeks, though for some babies it can take up to 8 weeks to fully settle.

Why it happens

At around 16 weeks, your baby's sleep cycles mature fundamentally:

• Sleep cycles become adult-like — alternating between light and deep sleep
• Between cycles (every 45-90 mins), baby briefly wakes — and needs help falling back asleep
• This is a sign of healthy brain development, not a problem

What actually helps

• White noise — mimics the womb, helps bridge sleep cycles
• Blackout curtains — melatonin production needs darkness
• Consistent bedtime routine — bath, feed, song, same order every night
• Early bedtime — overtired babies sleep worse, not better

What other mums say

"It lasted 3 weeks for us. The worst part was everyone telling me to 'just let her cry'. I didn't, and she got through it."

When to talk to your paediatrician

• If baby seems unwell (not just restless)
• If refusing feeds during the day
• If it doesn't improve after 8 weeks

This information does not replace medical advice.