The 4 Month Sleep Regression

4 month sleep regression

We hear it all the time. Parents are often baffled at the fact that their child slept wonderfully from birth until 4 months and then suddenly your baby is waking up more often, getting extra fussy at bedtime, and fighting sleep. It’s easy to get frustrated and start to panic- but there’s actually a biological reason for this sudden shift in behavior: the 4 month sleep regression. 

What is the 4 month sleep regression?

Between 3 and 4 months old, babies experience a “regression” – meaning their sleep patterns seem revert back to what they were as a newborn: only napping for 30 to 50 minutes at a time, staying awake longer between naps, and more frequent night wakings. 

However, the 4 month sleep “regression” is really more like a progression – your baby’s sleep cycles are developing and maturing!

What causes the 4 month sleep regression?

Around 4 months old, your baby’s sleep cycle changes, causing the effects of the 4 month sleep regression. Basically, for the first 3 months of their life, your baby immediately enters into REM sleep (light sleep) when they fall asleep. Between 3 and 4 months old, this changes. 

Now, they start to enter into a non-REM, deeper sleep stage once they fall asleep, which means their deepest sleep will be at the beginning of the night and will bounce back and forth between lighter periods of non-REM and more intense periods of REM sleep in the middle of the night. It’s during this 4 to 5 hour period where your baby is suddenly more prone to night wakings and will cry out for you to help sooth them back to sleep. 

Even though this sleep cycle transition causes more wakeups, it’s actually a good thing because this is the sleep cycle pattern that will continue for the rest of their lives. Essentially, they are switching to a more adult-like sleep cycle. 

It’s also the perfect age to start teaching baby to self soothe. 

4 month sleep regression

What are the signs of the 4 month sleep regression?

Once a child is through these middle of the night sleep cycles, they will then transition between deep non-REM and REM sleep for the remainder of the night. 

Have you noticed that it’s easier for you to wake in the middle of the night compared to a few hours after you fall asleep or when your alarm goes off in the morning? It’s because you are in a deep non-REM sleep stage. Now, the same thing is happening to your baby. 

When the 4 month sleep regression hits, you’ll notice your baby is waking up more frequently throughout the night. Your baby won’t nap as long as they used to, and probably won’t nap ‘on the go’ as easily as before. Babies are often fussier during the 4 month sleep regression and will try to fight sleep as nap and bedtime. 

The most notable thing with this regression is that it typically happens suddenly. You’ll have a sound-sleeping baby one night, and a fussy, overtired one the next. 

How long does the 4 month sleep regression last?

The 4 month sleep regression usually lasts about 2 to 4 weeks. During that time, your baby is learning how to adjust to their new sleep cycle – and teaching them how to self soothe will help make this transition easier. 

Some babies might experience the 4 month sleep regression for less time, others might take a little longer to go through it. The important thing to remember is that it is temporary! Your baby WILL sleep through the night…but until then, I’ve got some tips that can help. 

Tips for the 4 month sleep regression 

There’s a lot going on with your baby around the 4 month mark: they might be ready to drop a nap, could be learning to roll over, and their circadian rhythms begin to form, meaning they will thrive on routines and schedules. All of these things factor into sleep – so they’re important to keep in mind as you try to get through the next few weeks.

Nap time

During the 4 month sleep regression, baby won’t nap ‘on the go’ as easily and will do best having their naps at home, in their dark bedroom. I know it’s hard to be home for every nap, especially when they are happening 3-4 times a day. But if your baby could talk, they would be thanking you for respecting their sleep needs!

This is also the common time for baby to transition from 4 naps a day to only 3. The morning nap is established when it becomes consolidated (no waking and crying off and on) and baby wakes up happy and calm. The morning nap is mentally restorative while the afternoon nap is physically restorative. The 3rd (or 4th for babies who still need it) nap doesn’t have much restorative value. It’s basically used as a ‘carry over’ to get baby to bedtime without becoming overtired.


Since the 4 to 3 nap transition is bound to cause overtiredness (as do all nap transitions), setting an early bedtime is key to making sure your baby catches us on the lost sleep from dropping the 4th nap. 

During the first 4 months, Baby had a combination of short and long naps. Now that Baby is maturing; these short naps aren’t providing enough restorative value, which in turn is leading Baby to be overtired. Sounds fun, right?

Shifting bedtime up will help make sure your baby gets enough sleep which is incredibly important since they are also waking up more frequently throughout the night due to the 4 month sleep regression. 

Other 4 month sleep regression sleep tips

Make sure your baby’s sleep environment is conducive to sleep – it might help them transition from deep to light sleep stages more easily, therefore causing fewer wakeups. 

Keep your routines and schedules in place. You can be flexible during this challenging time, but stay on track as much as you possibly can. Your baby will thrive off this consistency and it will help them get back to sleeping longer stretches. 

Start thinking about sleep training, if you haven’t already. 16 weeks adjusted age is ideal for beginning sleep training – and since your baby needs to learn how to self soothe now more than ever, it’s a good time to start. 

Make time for tummy time during the day. As if there wasn’t already enough going on at 4 months old, many babies learn how to roll over at this age – and bedtime always seems like the best time for them to practice. By giving them enough time to practice during the day, they won’t be as distracted by their new skill at night. 

Speaking of rolling over, you need to start thinking about the swaddle transition as well. Once your baby shows signs of rolling over, it’s time to switch to a sleep sack.

As you can see, there are many things going on in baby’s life around 4 months old and, naturally, sleep will be affected by it all. But again, all of this is just a short phase in your baby’s life. You’ll BOTH be sleeping better in no time. 

For tips on the 24 month sleep regression, read this

Ferber, Richard. (2006). Solve your child’s sleep problems. New York, NY: Fireside.