What’s Going On with Sleep at Four Months?

If your once-sleepy newborn has suddenly started waking more often, taking shorter naps, or resisting bedtime… you’re not alone. Around the four-month mark, many parents notice a big shift in sleep, often called the four-month sleep regression, though I prefer to call it a progression.

Why? Because even though it feels like sleep is going backwards, your baby is actually growing and developing in amazing ways.

So, what’s really happening?

Around four months old, your baby’s sleep cycles mature. Instead of drifting between deep and light sleep like a newborn, they now start to move through more adult-like sleep cycles — including light sleep, deep sleep, and brief waking between cycles.

This means:

• They may start waking more frequently overnight.
  
  

• They might stir or cry at the end of a sleep cycle and need support going back to sleep.
  
  

• Naps can become shorter or harder to settle.
  
  

It can feel exhausting (because it is), but this shift is completely normal, and it’s a sign that your baby’s brain is developing just as it should.

Does it last forever?

No. The toughest part usually lasts a few weeks, but it’s often the moment where long-term sleep habits begin to form. Some babies start linking their sleep cycles independently over time. Others continue to wake and need help unless new strategies are introduced.

What can you do to support your baby through it?

• Look at your nap rhythm – Are they getting enough sleep during the day? Are wake windows appropriate for their age?
  
  

• Consider a calming, consistent bedtime routine – This helps their body and brain wind down.
  
  

• Offer support, but start giving space – Gentle settling methods can help them learn how to drift back off between cycles.
  
  

• Be kind to yourself – This phase can be hard. You're not doing anything wrong.
  
  

If things feel off-track and you're not sure how to move forward, you're not alone — and there are ways to make it easier.

The four-month progression is a turning point, and with the right support, it can lead to better sleep for everyone.