4 month sleep regression and how to handle it

What is the 4 month sleep regression and how to handle it

If you mention the 4 month sleep regression in any group of parents of babies and toddlers, most parents will shudder. As a Baby Sleep Consultant, I talk with parents every day about this regression and how to get babies sleeping again. The good news is that it will get better — even if it doesn’t feel like it right now. 

What is the 4 month sleep regression?

The 4 month sleep regression is caused by a biological change in the way that baby sleeps. That being said, compared to other sleep regressions (8-month, 18-month, etc.) that are typically caused by developmental milestones that baby moves through as they master those skills, the 4 month sleep regression is caused by a permanent change in the way babies sleep. 

In order to understand what’s happening to your baby during this stage, let’s talk about a few things about sleep in general first. Then we’ll get into why this sleep regression can wreak havoc on your sleep and what to do about it. 

While it may feel like you are either asleep or you aren’t, sleep has a number of different stages. These stages make up our sleep cycles, which we go through several times a night. There are 3 stages of Non-REM sleep and then REM sleep.

Stage 1

This is the initial stage of sleep that we’re all familiar with. You can feel yourself drifting off, but don’t really feel like you’ve fallen asleep. It is that head bobbing but doesn’t feel like you are fully asleep stage.

Stage 2

The first ‘true sleep stage is next. This is where people tend to realize, once woken up, that they actually were sleeping. For anyone taking a power nap, this is as deep as you want to go, or else you’re going to wake up groggy.

Stage 3

This stage is deep and regenerative, it is also known as slow-wave sleep. This is where the body starts repairing and rejuvenating the immune system, muscle tissue, energy stores, and sparks growth and development.

Stage 4 

REM (rapid eye movement) sleep is stage 4. This is where the brain starts to consolidate information and memories from the day before. It’s also the stage where we dream.

Once we’ve gone through all of the stages, we either wake up or come close to waking up. Then we start all over again until the alarm goes off.

4-month sleep regression

Newborn baby sleep versus sleep after the 4 month sleep regression

Newborn babies only have 2 stages of sleep: Deep Sleep and REM Sleep. They spend about half their sleep in each stage. Around the third or fourth month of life, there is a reorganization of sleep, as sleep matures into the pattern that they’ll continue to follow for the rest of their lives. 

On average, this change takes place when your baby is between 3 and 4.5 months old. (If your baby was born early, it may happen later because sleep is developmental.) Baby moves from 50% REM sleep to 25% in order to make room for those first two stages. Although REM sleep is light, it’s not as light as these two new stages that they’re trying to get used to. With more time spent in lighter sleep, there’s a much higher chance that they are going to wake up. 

We don’t want or need to prevent or avoid having your baby wake up. Waking up is absolutely natural and an important protection factor for babies Additionally, it is just how our bodies work. As adults, we wake up about four to eight or more times a night and even more in old age. 

What happens when we wake up during the night

When we wake up, our brain quickly surveys around to make sure we are safe. We recognize we are in our beds and everything is just like when we fell asleep. Then we are able to roll back into the next sleep cycle without even realizing we woke up. We typically don’t even remember these brief wake ups the next morning.

Your 4-month-old baby’s brain does the same thing. And now there are more wake ups because your baby is having more light sleep.

Signs of the 4 month sleep regression

If your baby seems to almost all of a sudden start waking up more frequently around the 4 month mark, it is very likely that their sleep cycles are maturing and they are going through the 4 month sleep regression. It can often feel like things may be getting worse, or at least not getting better as the days and weeks go on.

The common challenge during the 4 month sleep regression

The challenge with the increased wake ups comes in when your 4-month-old baby falls asleep with the help of parent or caregiver dependent sleep associations such as feeding, rocking, pacifier, bouncing, etc. While these sleep associations seem to help get your baby to sleep faster and easier, they become an issue when your baby is put down asleep and those things are no longer present when your baby wakes up. When they realize that things are different, they become wide awake and then they may not know how to get back to sleep because they are used to those external sleep associations to get to sleep.

Then they are calling out for help because they need that situation recreated (or something similar) in order to get back to sleep. This results in both babies and parents being up even more frequently for parents to put their baby back to sleep.

Is this sleep regression a normal milestone?

While this can be a tough milestone for parents and babies alike, it is a very normal milestone. It really is a ‘progression’ rather than a ‘regression’ because the cause of these extra sleep disruptions and shorter stretches of sleep is babies growing and maturing as they should.

How long does the 4 month sleep regression last?

Since the 4 month sleep regression is a permanent maturation of your baby’s sleep cycle, it isn’t usually something that just ends. Especially if your baby has been helped to sleep with parent-dependent sleep associations.

If you have been working on independent sleep with your newborn, your baby will still likely be impacted by this change in their sleep. However, it is more likely in these situations where your baby was falling asleep independently, that they will continue to be able to fall and stay asleep independently after a short disruption as they adjust to their new sleep pattern.

Is this the same as the 3 month and 5 month sleep regression?

There is a lot of development going on in babies’ brains and bodies between 3 to 5 months. So there could be multiple factors impacting your baby’s sleep during this time. However, the 4 month sleep regression is a developmental change all babies go through so, especially when you are seeing continued challenges beyond a week or so, the 4 month sleep regression is likely a part of the sleep disruptions you and your baby are experiencing during this age range.

Other developmental changes around the 4 month sleep regression

Not only is your baby’s sleep patterns changing, there are also other big pieces of development happening that can impact sleep.

Reduction in sleep needs

Babies’ sleep needs decrease from about 14-18 hours in a 24 hour period to around 12 to 15 hours in a 24 hour period. Often babies are needing longer wake windows (between 1.25-2 hours) in order to build up enough sleep pressure to get to sleep and stay asleep. 


Babies often start rolling around this age. Big developmental milestones like this can also disrupt sleep. Their brains prioritize learning these skills over sleep and it can lead to extra wake ups where your baby is practicing their skills (and possibly getting stuck on their tummy and needing help getting back to their back. More on tummy sleeping here.)

At this age, it is important to transition your baby out of their swaddle if they are still swaddled. This is especially important if your baby is rolling or showing ANY signs of rolling, even if you aren’t seeing these signs just sleep periods. This helps keep your baby safe while sleeping as they become more mobile. (More tips on this transition here.)

Daytime Interaction

​​Babies are often becoming more interactive, wanting to play more and developing FOMO (fear of missing out). These can also make sleep more challenging because babies want to continue to be involved in the day and sharing life rather than separate for sleep. (Presenting sleep as a beautiful thing and endearing them to the process can help!)

Sometimes this also presents as the previous ways of getting your baby to sleep (feeding, rocking, bouncing, pacifier, etc.) aren’t working anymore! 

How to manage the 4 month sleep regression

The cause of the 4 month sleep regression is a real biological and permanent change. This brings up the big question: What can you do to help your little one adjust so the pain and sleep deprivation don’t start to feel permanent?

Here are four absolute musts and the first place to start in improving sleep during the 4 month sleep regression.

1. Darkness

Baby’s room should be dark, dark, dark! Get some blackout curtains or get creative with trash bags or even foil and get the room dark.

Darkness tells babies’ bodies and brains to release hormones like melatonin, that help with sleep at night. It also limits visual stimulation so your baby can focus on sleep.

If your baby has a reaction to their newly darkened room it is usually related to the change itself, not being scared of the dark. 

2. Sound

Sound is the strongest sleep cue for babies 12 months and younger and white noise is a great one because it is a consistent sound without the ups and downs and changes in pitch of lullabies, for example. Additionally, it can drown out external noises that may contribute to your baby waking up.

Turning it on right before you put your baby down to sleep will help them recognize white noise as something that happens when it is time to transition to sleep, making it easier for their brain and body to fall asleep. (I recommend the Hatch, because it will grow with your child!)

3. Routine

Bedtime routines are also an essential component to getting your baby sleeping well. This is because your baby will recognize these steps happen each day before the transition to sleep. Then their body and brain are able to anticipate the transition to sleep coming, allowing them to fall asleep easier and more quickly. Try to keep the routine to about 4 or 5 steps, lasting 20-30 minutes or so. 

Try to keep the feed near the beginning of the routine so they can fill their tummies while wide awake. Then you can do a baby massage while getting on cozy pajamas, read a story or two and sing some special, calming songs before turning on the white noise and putting your baby into their crib. 

4. Avoid overtiredness

If you’re noticing your baby is getting fussy before bedtime or during their bedtime routine, you probably waited too long. Aim for a bedtime between 6:30-8:00 PM, keeping in mind that 4 month olds are typically only able to go about 2 hours between sleep periods. Keeping your baby awake longer than this can result in them becoming overtired.

Overtiredness is a common cause of challenges getting to sleep, staying asleep and waking up super early in the morning.

Teaching Independent Sleep Skills

Helping your baby learn to fall asleep independently can help both of you because when they wake up between sleep cycles, they will know how to easily and quickly (without even remembering it usually!) get themselves back to sleep. So you won’t need to help them recreate the situation for falling asleep multiple times throughout the night because it won’t have changed. (Don’t worry, when your baby needs something other than sleep such as a feed or to have their diaper changed, they will call out to you.) 

Can you sleep train during the 4 month sleep regression?

Helping your baby learn how to fall asleep independently can greatly improve the sleep disruptions caused by this regression. So yes, you can sleep train while in the midst of this sleep regression.

Learning independent sleep skills, also known as sleep training, involves putting your baby down awake in their crib and allowing them to fall asleep on their own. This does NOT mean you have to shut the door, walk away and let baby cry-it-out. There are many methods and strategies of sleep training, you have to find what works for your family that you feel confident being consistent with. Consistency is key so your baby is able to learn what to expect and really develop their skills to settle themselves to sleep. You can absolutely be present, responsive and soothing during the process. 

Some kids learn new skills like this quickly. But, some are going to be a little more resistant and need more help to learn and master the skills to sleep independently. Here are Sleep Love and Happiness, we work with parents to find the middle ground between cry-it-out and wait-it-out. 

Gentle and Compassionate Sleep Training for you and your baby

If you are struggling with your baby’s sleep, aren’t sure what steps to take or what to do next, you are in the right place! We help parents every day with respectful sleep training strategies that meet their family where they are at. 

If you’re beyond exhausted, wandering around like a zombie and just want to see a light at the end of the tunnel, now is absolutely the time. There is a light at the end of the tunnel – reach out today to learn more about how a personalized sleep plan for you and baby can get your whole family sleeping better! 

Cheers to healthy, happy sleep!


**Updated July 2023**

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