The 4-Month Sleep Regression: What’s Actually Going On

Let’s talk about the dreaded 4-month sleep regression.

If your baby was sleeping pretty well and suddenly starts waking up every 45 minutes, fighting naps worse than before, or just seems super cranky and overtired all day long… this might be the culprit.

But here's the thing: it’s not really a “regression”—it’s actually a progression. Let me explain.

So, what is the 4-month sleep regression?

Around 3.5 to 4.5 months old (give or take), your baby’s sleep cycles permanently mature. Until now, they’ve been sleeping more like a newborn—drifting in and out without full sleep stages like adults do. But now? Their brain starts organizing sleep into more adult-like stages.

That means instead of gliding easily from one sleep cycle to the next, they start waking between cycles. And if they haven’t learned how to fall asleep independently yet, they’ll likely need you to help them back to sleep. Again. And again. And again.

You might notice:

• Increased night wakings

• Short, 20–30 minute naps

• Fussiness or seeming overtired all day

• Needing to be rocked or fed to sleep more than usual

  
  

It's tough. But it’s also totally normal. And it’s not your fault.

What’s actually going on during this time?

This is a major developmental milestone. Your baby’s brain is growing rapidly and their sleep architecture is reorganizing itself.

It’s also the age when babies become more alert to their surroundings—and they notice when things change. Like: “Hey! I fell asleep in mom’s arms but woke up alone in my crib? What gives?!”

They’re also possibly going through a growth spurt or learning new motor skills. So their body and brain are basically in overdrive.

Okay… so what can you do to survive it?

Let’s get to the good stuff.

1. Start a consistent bedtime routine. If you haven’t already, now’s the time to create a predictable wind-down routine. It helps cue your baby’s body and brain that sleep is coming.

2. Use wake windows to avoid overtiredness. At 4 months, most babies can stay awake for about 1.5 to 2 hours max between naps. Keeping a close eye on those windows helps prevent overtiredness, which actually makes sleep worse.

3. Try putting baby down awake. If your baby is used to falling asleep at the breast or being rocked, start practicing laying them down a bit more awake. It teaches them to fall asleep where they’ll be waking up—in the crib.

4. Stay consistent with night wakings. If your baby is waking frequently, decide what you’ll do when it happens—feed? soothe? wait a few minutes?—and try to stay consistent. Predictability helps.

5. Don’t panic. This doesn’t last forever. Sleep may feel a little wild for a few weeks, but things can and do improve with the right foundation.

Want help building that foundation? I walk you through this exact stage in my sleep course for 4–24 month olds or we can work 1:1 to get things on track even faster. You don’t have to wait this out alone.

You’ve got this, Mama.

Your Sleep BFF,

Melanie