4 month sleep regression and how to handle it

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. 

Let’s start with what causes the dreaded 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 

A 4-month-old baby’s brain does the same thing. The challenge comes in when the 4-month-old baby, who fell asleep with the help of their parent or caregiver or something external to them (feeding, rocking, pacifier, bouncing) and then is put down, realizes that things are different and has a full wake up. They become wide awake and then they may not know how to get back to sleep because they are used to that external help to get to sleep. Then they are calling out because they want to go back to sleep but need help to recreate a situation in which they are used to falling asleep. 

Now that your 4 month old is having more light sleep and therefore is more easily woken up, this external help in getting to sleep can create a quite challenging situation.

Sleep associations like feeding, rocking, bouncing, pacifier, etc. help get your baby to sleep faster and seemingly easier but they become an issue when those things are no longer present during the night when your baby wakes up.  

You can compare this to if you went to sleep in your nice comfy, cozy bed and all of a sudden you wake up and realize you are out on your front lawn. You are going to be pretty alarmed.

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.)

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! 

Some good news about the 4 month sleep regression

So, some good news for anyone experiencing the dreaded 4 month sleep regression is that it is, in fact, a progression. Now it doesn’t feel like that when your baby went from the sleeping 4-5+ hour stretches down to 1-2 hour stretches all night, but it is a progression in their development as sleep matures.

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?


Baby’s room should be dark, dark, dark! I mean a clear, moonless night kind of dark. Get some blackout curtains, Tape garbage bags over the windows or cover them with tinfoil. Get creative and get the room dark.

Newborns and infants are not afraid of the dark. They don’t have the cognitive capacity to imagine scary things in the dark. When a baby has a reaction to their newly darkened room it is usually related to the change itself, not being scared of the dark.

However, they are very responsive to light. Light tells their brains that it’s time to be active and alert. Then their brain secretes hormones accordingly. So we want to keep their nursery as dark as possible during naps and bedtime. This allows their bodies and brains to release the hormones that help with sleep, such as melatonin. 

Darkness also helps limit stimulation so your baby isn’t looking around at everything in their room instead of focusing on sleep. 


The other nemesis of daytime sleep, (and nighttime for that matter, although not nearly as often) is noise. Whether it’s the Amazon delivery person ringing the doorbell (it’s cool you don’t need to ring the doorbell, my app alerts me that you delivered my package), or the dog warning you that the squirrels are back and for sure going to attack the house this time (yup, this is absolutely the time we are all in real danger, thanks for letting me know!), or something falling on the floor three rooms away, there is always some noise that can wake up baby. With baby spending more time in lighter sleep, noises can startle them easily and wake them up. If you don’t have one already, a white noise machine is a great addition to your nursery. (I recommend the Hatch, because it will grow with your child!)

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. 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. 


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 plan on getting into cozy pajamas, reading a story or two and singing some special, calming songs before turning on the white noise and putting your baby into their crib. 

If you’re noticing your baby is getting fussy before bedtime or during their bedtime routine, you probably waited too long. Four-month-old babies should really only be going about two hours at most between sleep periods. Bedtime should be between 6:30 and 8:00 PM at night.

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.) 

Learning independent sleep skills 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!


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