The Four Month Sleep Regression

May 18, 2020


Every time I do a Q&A or meet with a parent group I'm asked about sleep regressions. Parents are finding literature about a loss of skill at 4 month, 9 month, 12 month, 18 month, 2 year... it's mind hard to keep track of! Typically, once I get to the bottom of the sleep problem, I discover it's simply "getting off track" after teething, travel, or major transitions. 


However, the four-month regression, everybody agrees on, and for good reason. It’s the real deal, and it’s permanent.


In order to understand what’s happening to your baby during this stage, first you need to know a few things about sleep in general. So here’s the science-y part, simplified.


Many of us just think of sleep as an on-or-off situation. You’re either asleep or you’re not. But sleep actually has a number of different stages, and they make up the “sleep cycle,” which we go through several times a night. 


Stage 1 is that initial stage we’re all familiar with where you can just feel yourself drifting off, but don’t really feel like you’ve fallen asleep. Anyone who has ever seen their partner nodding off in front of the TV, told them to go to bed, and gotten the canned response of, “I wasn’t sleeping!” knows exactly what this looks like.


Stage 2 is considered the first “true sleep” stage. 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 is deep and regenerative. Also known as Slow Wave sleep, this is where the body starts repairing and rejuvenating the immune system, muscles tissue, energy stores, and sparks growth and development.


Stage 4 is REM (rapid eye movement) sleep. This is where the brain starts to kick in and consolidates information and memories from the day before. It’s also the stage where we do most of our dreaming. 


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


What does this have to do with the dreaded four month sleep regression?


Well, newborn babies only have two stages of sleep; stage 3 and REM, and they spend about half their sleep in each stage. But around the third or fourth month of life, there is a reorganization of sleep as they embrace the 4-stage method of sleep that they’ll continue to follow for the rest of their lives. 

When this change takes place, baby moves from 50% REM sleep to 25% in order to make room for those first two stages. So although REM sleep is light, it’s not as light as these two new stages that they’re getting used to, and with more time spent in lighter sleep, there’s more of a chance that baby’s going to wake up. 


That’s not to say that we want to prevent or avoid baby waking up. Waking up is absolutely natural, and we continue to wake up three, four, five times a night into adulthood and even more in old age. 


As adults, however, we’re able to identify certain comforting truths that baby might not be privy to. When we wake in the night, we’re able to recognize that, “Hey, I’m here in my bed, it’s still nighttime, my alarm isn’t going to go off for another three hours, and I’m reasonably certain that there are no monsters lurking under my bed. I can go back to sleep”And we do. Usually so quickly that, the next morning, we don’t even remember the brief encounter with consciousness.


A four month old baby, of course, lacks these critical thinking skills. To a four month old baby who fell asleep at her mother’s breast, the reasoning could go much more to the tune of, “OK, last thing I remember, there was a familiar, beloved face, I was having dinner, and someone was singing me a soothing song about the stars... Now I’m alone in this dark room, there’s no food, or a warm body, I'm all alone and it feels very unfamiliar", and it makes sense to call out for the familiar comforts.


The other major contributor to this four month fiasco, is that up until this point, parents have either been putting their baby to sleep with a pacifier, or by rocking them, or by breastfeeding them, or some similar technique where baby is helped along on the road to falling asleep. 


Now that baby’s spending more time in light sleep, and therefore has a higher probability of waking up, this suddenly becomes a much bigger issue. These sleep props or sleep associations can be very sneaky indeed, because although they may be helpful in getting your little one to that initial nodding off stage, the lack of them when they wake up means that baby’s not able to get back to sleep again without some outside help. Cue the calling out, crying, fight-or-flight, and the adrenaline. When this starts happening every half an hour, parents can find themselves in a nightmarish situation.


The good news for anyone experiencing the dreaded Four Month Sleep Regression is that it’s not, in fact, a regression at all. A regression is defined as “reversion to an earlier mental or behavioral level,” and that’s actually the opposite of what your baby is experiencing. This would be much more aptly titled the “Four Month Sleep Progression”


Here's what you can do to help your little one adjust


First off, make sure that baby’s room is VERY dark.  You might think that baby’s room is dark enough, or that baby might not like the dark, and that it’s comforting to have a little bit of light coming through the windows or seeping in from the hallway. 




Baby’s room should be dark. I mean coal mine on a moonless night kind of dark. Tape garbage bags over the windows if you have to, or cover them with tinfoil. (You can throw me under the bus if your neighbors question your home decor.)


Newborns and infants are not afraid of the dark. They are, however, responsive to light. Light tells their brains that it’s time for activity and alertness, and the brain secretes hormones accordingly, so we want to keep that nursery absolutely pitch black during naps and bedtime. 


Second, turn on the white noise. The other nemesis of daytime sleep, (and nighttime for that matter, although not nearly as often) is noise. Whether its UPS ringing the doorbell, the dog warning you that the squirrels are back and for sure going to attack the house this time, or something falling on the floor three rooms away.


With baby spending more time in lighter sleep, noises will startle them easily and wake them up, so white noise is a great addition to your nursery. I recommend spending your money on a desktop air filter that will also create a healthier environment as it blocks disruptions. 


Third, avoid over-tiredness. At 4 months the average baby can go 90minutes to 2 hours between snoozes. If pushed beyond that it's likely they will re-alert and require lots of assistance (aka sleep props) to finally calm down and go to sleep. 


Now, there are going to be occasions that sleep gets off track later on in your little one’s youth. Traveling, illness,  cutting teeth, all of these things can cause your little one to have a few bad nights of sleep. But when it comes to the four month “progression,” I’m happy to report that this is a one-time thing. Once you’re through this, your baby will have officially moved into the sleep cycle that they’ll essentially be following for the rest of their life; four glorious stages repeated multiple times a night. 


By taking this opportunity to teach them the skills they need to string those sleep cycles together, independently, prop-free, without any need for nursing, rocking, or pacifiers, you’ll have given them a gift that they’ll enjoy for the rest of their young lives.


I find these baby gadgets to be priceless for easing into the four month regression, and I've included my affiliate links here if you cannot find them locally: 


Love to Dream Swaddle - transition to rolling with comforting, calming safety. 

Yookidoo Tummy Time Mat - build skills the fun way. 

Organic Cotton Crib Sheet - Babies spend so much time sleeping - let it be on organic cotton. 

Lamaze Counting Animals Soft Book - an age-appropriate addition to your bedtime routine


Of course, some kids are going to take to this process like a fish to water, and some are going to be a little more resistant. If yours falls into the former category, count yourself as lucky, take delight in your success, and go ahead and gloat about it on Instagram, for sure!  


For those of you in the latter camp, I’m happy to help in any way I can. I have created a Newborn Sleep Class that helps teach sleep skills so families can avoid the problems related to the four month regression altogether. Set up a free evaluation call to talk about your concerns sooner rather than later. 


The most common thing I hear after talking with families is, “I can’t believe I waited so long to get help!” So reach out now for support and reassurance that will save you worry (and your little one tears) in the future. 



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Kristine Petterson 

Sleep & Mindful Parenting Specialist 

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