The 4-Month Sleep Regression Explained: Causes, Solutions, and What Not to Do

The dreaded 4 month sleep regression. 

Before I experienced it firsthand, I didn’t even know it was a thing. My first baby had the erratic sleep patterns of a newborn, but by 6 weeks, she was stretching her nights longer and taking blissful naps on my chest. I thought I had hit the baby sleep jackpot.

At her four-month check-up, when the doctor asked how she was sleeping, I excitedly told her how great of a sleeper she was. Her doctor smiled knowingly and said, “I hope it stays that way.”

I shrugged it off until, seemingly overnight, my champion sleeper started waking up every 2 hours. Naps became a fight, and nights blurred into endless rocking, swaying, and feeding. What had happened?

The 4-Month Sleep Regression 

We had entered a phase commonly called the 4-month sleep regression. This isn’t a “regression” in the sense that your baby is going backward, though it feels like it when it comes to sleep. In reality, it’s a progression – a massive leap forward in brain development that completely changes how your baby sleeps.

Dr. Erin Flynn-Evans, a sleep scientist and author of Baby Sleep Science Guide: Overcoming the Four-Month Sleep Regression, explains this is when babies shift from newborn sleep cycles (only two stages) to adult-like sleep patterns (four distinct stages).

This shift means:

• More wake-ups between sleep cycles (instead of drifting seamlessly into the next one)

• Increased melatonin production

• Stronger sleep associations (meaning, how they fall asleep matters more than ever)

What’s Happening to Your Baby’s Sleep?

1. Sleep Cycles Become More Defined

Newborns drift through sleep without much structure. Now, your baby is cycling between light and deep sleep, just like adults do. The difference is that adults know how to put themselves back to sleep and babies don’t.

2. More Frequent Wake-Ups

Since your baby now has distinct sleep cycles, they’re more likely to wake fully at the end of each one. This is why naps are suddenly 30-45 minutes long and they wake every two hours overnight.

3. Increased Awareness

At this stage, your baby is much more aware of their environment. If they fall asleep in your arms but wake up alone in their crib, they notice. My favorite example for this is to think of the scene in The Parent Trap where Meredith Blake wakes up in the middle of the lake after falling asleep in her tent–you’d be upset too!

How to Help Your Baby Sleep Better (Without Losing Your Mind)

When our babies suddenly start panic crying in the middle of the night, it’s human nature to want to comfort them. We pick them up, rock them, sing to them, or try to give them their paci. When these things don’t work, we usually try feeding them. 

Unfortunately, these can create pretty strong sleep associations. Instead, try these suggestions:

1. Create a Sleep-Friendly Environment

Your baby’s new sleep cycles mean they’re more sensitive to disruptions. Optimize their space:

• Dark Room: Even small amounts of light can disrupt melatonin production. Use blackout curtains (or a SlumberPod if room-sharing). A red light can be useful for night feedings.

• White Noise: Masks environmental sounds and promotes longer sleep stretches.

• Consistent Sleep Space: If possible, have your baby sleep in the same place for naps and nighttime sleep.

2. Break the Feed-to-Sleep Cycle

If your baby is nursed or bottle fed to sleep, they’ll expect it every time they wake up.

Try this instead:

• Shift feeding to the start of the bedtime routine.

• Gradually reduce rocking or bouncing before placing baby down.

• Each night, try to put baby down a little more awake to break the feeding-to-sleep habit.

3. Introduce a Bedtime Routine

While it seems silly to have a bedtime routine this young, it helps signal to your baby that sleep is coming and causes the hormone adrenaline to decrease, helping them relax. 

Keep it simple:

1️⃣ Bath (optional—you don’t have to do it every night!)
2️⃣ Pajamas
3️⃣ Feeding (but not to sleep)
4️⃣ Story or lullaby
5️⃣ Into the crib fully awake

(Pro tip: “Drowsy but awake” can be tricky. A too drowsy baby is already halfway asleep, meaning they’ll wake up expecting the same conditions. Try placing baby down as awake as possible.)

4. Support Self-Soothing (Gradually)

One of the biggest sleep disruptors at this stage is that babies haven’t yet learned to resettle themselves.

• Pause before rushing in. Some babies fuss briefly in their sleep and don’t actually need intervention.

• Try a hands-on approach. Gentle tummy pats, rubbing between their eyes, or offering a pacifier (if they can replace it themselves).

• Avoid excessive rocking or bouncing. The goal is to teach baby to settle with less help over time.

5. Watch Wake Windows

It goes against all natural logic, but overtired babies actually sleep worse, not better. Make sure your baby is getting the right amount of daytime sleep and isn’t staying awake too long between naps:

• 3 months: 1 hour 15 minutes of awake time

• 4 months: 1.5 hours of awake time

• 5 months: 1 hour 45 minutes of awake time 

Keeping an eye on wake windows can help prevent overtired meltdowns.

What NOT to Do

Don’t assume it will just “fix itself.”
This isn’t a phase unfortunately but a permanent change in how your baby sleeps. If they rely on motion, feeding, or other sleep props, they will continue waking for them.

Don’t introduce new habits you don’t want long-term.
It’s tempting to do whatever works to get through the night (I’ve been there). But if you don’t want to do it for months, try adjusting now.

Don’t panic, this is normal.
Every baby goes through this. It’s hard, but it’s also a sign of healthy brain development.

This Phase Won’t Last Forever

I know how exhausting this is, but try to remember that your baby is learning and this is all so new to them. 

Right now, their brain is doing exactly what it’s supposed to do—growing, developing, adapting. As overwhelming as it feels, this phase won’t last forever.

With the right approach (consistent routines, self-soothing opportunities, and a sleep-friendly environment) you can help your baby sleep better.

And one day, you’ll look back and realize this was just a tiny (albeit exhausting) phase in your parenting journey.