What Is The 4 Month Sleep Regression?

sleep training baby

So your baby has hit 4 months old and something has changed. You don’t know what it has caused it but suddenly they are extremely fussy or crying inconsolably at bedtime; struggling to fall asleep or stay asleep; baby wakes several times per night; naps have become short and difficult; and quite simply, you haven’t a clue why or how this has happened. But the sleep deprivation is very real.

Well, this will be the 4 month sleep regression. Before I tell you you how you can try to manage it as best you can, let me tell you what a sleep regression is.



A sleep regression is when a child’s sleep goes backwards. For example, they stop settling to sleep so easily; they have more wake ups in the night; naps becomes shorter and more challenging. These sleep regressions are usually driven by your baby going reaching a developmental milestone, cognitive or physical.

This can be challenging for parents as it’s lovely seeing some of those developmental milestones being hit, but it can also impact the whole family’s sleep as a result.

Some of the big changes which lead to a sleep regression are:

  • Growth Spurts

  • Physical development such as rolling, standing, cruising, walking

  • Language developing, even in babies who aren’t closet to speaking

  • Separation anxiety

  • Independence development, especially for toddlers



Whilst a sleep regression usually arises due to a child hitting a developmental milestone as outlined above, there are other factors which can lead to sleep regressing, including, but not limited to:


There is nothing you can do stop sleep regressions happening as most of it is a normal – and good! – part of your baby or toddler’s development. All, you can do is have the information and knowledge to manage it as best you can until it passes.

baby yawning whilst being swaddled


This is very dependent on the baby as not all babies will show the same signs, but the below are typical symptoms of the 4 month sleep regression:

  • Sudden difficult to fall asleep at night and in the day

  • They wake more frequently in the night and an overall reduction in sleep amount over a 24 hour period

  • Sudden or increased resistance to daytime naps and/or short naps

  • Sleep schedule has changed and nap times are all over the place

  • Irritable mood; unable to be put down on their back 


Sleep regressions typically last anything from two to six weeks but my experience shows that it’s more typical to last around two weeks. This is where it can often become difficult for some parents to differentiate between their child’s sleep patterns being related to the regression, baby sleep habits generally, or teething starting.

If you feel that your 4 month sleep regression has lasted longer, you may need some help to change it. My online sleep courses can make changes to your child’s sleep patterns in just 10-14 days.



The 4 month sleep regression is a highly searched term of Google and other search engines. Often parents have just started seeing some improvement in sleep from the newborn stage and then in an instant, it goes downhill.

Suddenly the tiny baby is struggling to fall asleep and stay asleep, waking multiple times overnight, not sleeping enough over a 24 hour period, and is unable to fall asleep anywhere but on parent or the buggy.

There are a number of factors that lead to this inevitable regression at 4 months:

  • Their sleep physiology is developing from newborn sleep to that of sleep cycles, something they will continue with into adulthood.

  • Their social awareness is developing.

  • They may be having a growth spurt.

  • They may start rolling at this time too.


There is A LOT going on, but the biggest driver is the first point – their change in sleep physiology when babies start sleeping in cycles. Whilst you can be told as a parent that it’s actually a great development for your baby, it won’t feel like that when it happens.

We’ve been through it as a family three times and it’s not fun, though not all babies’ sleep is significantly impacted.



The Sleep Cycle is what humans do – after the 4 month sleep regression! – do during sleep, day or night. Understanding how sleep works in children can help us to work out suitable methods for establishing healthy sleep habits.

Light sleep and deep sleep alternate in approximately 45 minute sleep cycles for young children (approximately 90 minutes in adults) which is shown in the diagram below (you will notice that babies are only in deep sleep for about 10 minutes of a sleep cycle, with the remaining time being spent in light sleep).

In between sleep cycles, all humans ‘wake’, albeit briefly so most people don’t remember them at all. These ‘wakes’ during the night are completely normal, but it’s the inability to get into a new sleep cycle after these wakes which can cause sleep problems.

A sleep cycle diagram


If a baby has been using an external sleep associations to help them get into their first sleep cycle, or back to sleep from a wake during the night, they will continue to seek that external comfort again and again (even if it’s not for all sleep cycles each night).

Teaching our babies how to self-settle and not require one or more sleep associations to enable to them to fall asleep, is a really key part of independent sleep.

One of the most challenging things about the 4 month sleep regression is that it often coincides with a baby learning to roll. Not only are parents having to cope with signficant reduction in sleep in the household, they are now having to watch their baby roll onto their front and the natural safety concerns that come with it. Trust me, even after 2 kids, our 3rd baby learning to roll wasn’t any less scary. But it does get easier, I promise. 

beautiful baby girl in bow yawning


A regression can last anything from two to six weeks but my experience shows that it’s more typical to last around two weeks. This is where it can often become difficult for some parents to differentiate between their baby’s sleep patterns being related to a regression, your baby’s sleeping habits generally, or the after-effects of a previous regression.

Unfortunately, many of my 1:1 clients come to me 2 or 3 months after the 4 month sleep regression and they aren’t sure if the regression has ended or not. However, it’s clear that it has ended but some of the sleep habits introduced have continued which is what we are experts in resolving.

If you feel that the regression has been going on too long and it’s probably now something else, my online sleep training courses will allow you to make significant improvements to your baby’s sleep in just a couple of weeks. 



If only! It’s very rare for a baby to give their parents a bit of notice that a regression is brewing. It usually happens one bedtime or nap all of a sudden, so there isn’t unfortunately much you can do as a parent to prepare for the change you will see in your baby’s sleep pattern.



Teething often starts to impacting babies around the 4 month mark (as if their sleep physiology changing wasn’t enough!). But how do you know if it’s the 4 month sleep regression or teething that is impacting your baby’s sleep?

There are a few things to think about when trying to understand whether it’s the regression or teething:

  • Even with teething, a baby doesn’t always wake up every 40-45mins which can happen during the 4 month sleep regression

  • A baby that is teething will often be putting their fist in their mouth when they wake

  • Teething will be obvious during the day too with rosy cheeks, more drooling and a change in poos



How the 4 month sleep regression impact babies completely varies. However, it doesn’t usually just impact naps. Because of the complete change in a baby’s sleep physiology, it’s going to impact any time your baby is due to sleep. 

beautiful dark eyed little baby with hand near mouth


In short, the changes at the 4 month mark always happen. However, not all babies suffer from a big impact during this period and some babies fall asleep like they did before the regression. We’ve been through it three times now and the below is the impact we had for our children:

Baby 1:

Very unsettled during the night, though not every night. Daytime sleep was not too impacted thankfully

Baby 2:

He had been sleeping through from 11 weeks and during the 4 month sleep regression, only woke once for a bottle during the night for one week. Very little impact.

Baby 3:

Also slept through the night from 11 weeks but was hugely unsettled during the night for around 14 days. Some of this was due to the fact he had also learned to roll. Daytime and bedtime settling was much more challenging during the regression.



For babies who were born prematurely, the 4 month sleep regression can actually be a good way of determining your child’s age of sleep development and when they may hit other milestones.

Whilst I wouldn’t necessarily expect a baby who was born 2 months early to be hitting the 4 month sleep regression at 4 months since birth (2 months corrected), I have definitely seen situations where preemie babies hit the regression a little earlier than their corrected age.



The 4 month sleep regression can definitely happen earlier, even for babies born full-term. I would say that it’s unlikely for the regression to be happening at 12 or 14 weeks, but from 15-16 weeks on it wouldn’t be impossible.



Below, I have listed my top strategies to follow for most sleep regressions that occur:

baby boy with blue eyes and mouth open

Comfort, comfort, comfort

  • Please don’t not comfort your baby when a sleep regression happens. They are going through a significant change and need your support to help with them with this. However, it’s about striking the right balance between comforting them to the point they need your full support to fall asleep and allowing them to continue to fall asleep independently in their own sleep space.


A fuss and a whinge from a baby is fine

  • You may choose not to respond to your baby initially when they do some whingeing or fussing during the night. Giving them some space can be really be powerful for allowing them to fall back asleep independently.


Be mindful of how you help support them falling asleep

  • If your baby wasn’t hungry during the day, would you feed them? It’s the same at night but babies will often take it as a comfort when they are upset which can then lead to their reliance on it whenever they wake the next night, and the night after that…


Try to keep them in their cot

  • If you are happy co-sleeping, ignore this point. However, if you don’t want to be co-sleeping in the future, I would advise you not to bring your baby into your bed at night during a regression. Whilst some babies don’t want to co-sleep, other babies don’t need a second invitation and can start waking each night for that invite!


Consistency is key

  • Maintain consistency as much as possible with everything around your baby’s routine, especially their bedtime routine. It’s the same with their sleep environment; for example, if you use white or pink noise, continue using it during a sleep regression.


Pay close attention to your baby’s sleep cues

  • Closely monitor your baby’s sleepy cues and wake windows Falling asleep is much easier for a baby who is tired, but not overtired so try to put in their cot for sleep when they are ready rather than sticking to a fixed routine..


Try to maintain good sleep habits

  • Even for The Daddy Sleep Consultant team, this can be difficult as it’s a tough period. However, if I could give you one bit of advice, it’s to try and not introduce sleep patterns that are not sustainable or that you don’t want longer-term, though do balance this off with providing your child with the support they need during this difficult time. Also, be kind to yourself.


baby held over parent's shoulder


The other main regression ages are at 8 months and 18 months, though any big developmental milestone can lead to a small regression for you baby.


The next big one is the 8 month sleep regression. Whilst the main drivers of this regression is different to the regression at 4 months, it’s still related to your baby’s developmental milestones and you will likely face issues with your baby falling asleep. The milestones linked to this regression include:

  • Separation anxiety is developing further.

  • Your baby is likely learning to crawl, stand or even cruise around the house.

  • There will be new bouts of teething.

  • Baby’s wake window is lengthening and is likely dropping from 3 naps to 2 naps. 


baby with blue eyes lying on back looking to the side


Also known as the toddler sleep regression, the 18 month regression happens around 18 or 19 months.

This is all about a baby transitioning into the world of toddlerhood, and more independency. This can lead to bedtime and nap time battles, and many children drop their nap around this time because of those battles, even though they are nowhere near ready to do without daytime sleep.

toddler with hand in mouth resting on their front

My middle child was very impacted around this age due to separation anxierty as he had a deep desire to show his independence. Additionally, whilst he could understand so much of what we said, he struggled to verbalise responses which made him more frustrated.

This regression can also coincide with a parent’s decision to move their infant to a “big boy” or “big girl” bed, often to do with those bedtime battles I referred to. Parents often see those bedtime battles as their child telling them they want to be out of a cot and in a bed like adults. Unfortunately, this can be a little too much independence for what their little bodies and minds can handle at this stage.

Therefore, my advice here is quite simple: don’t move them from a cot to a toddler bed unless a) you want to and/or b) they are climbing out of their cot and there’s a safety issue. We have kept our children in their cots as long as possible every time and we feel that has made the transition to the toddler bed much, much easier for them and for us.

Another factor which may input into this sleep regression is potty training. 18 months is an age many parents start thinking about transitioning their little one from nappies to pants. As you can imaging, with such a significant life change, there can be an impact to toddler sleep patterns.

Finally, just like with the dropping of a nap at 8 months, some toddlers don’t drop to one nap until 18 months. My second child actually only moved to one nap consistently at 19 months, with 2-3 months of straddling between 2-nap days and 1-nap days. During any nap transition, you will likely see some impact to sleep with overtiredness usually the key factor.



If the regression feels like it’s becoming the 5 month or 6 month sleep regression, there is a very good chance that the regression has passed, but your baby has got used to the extra comfort you provided and is now reliant on it for helping them fall asleep.

If this is the case, you may require some gentle sleep training support from one of our sleep consultants. Contact us today or book a free initial consultation to discuss our 1:1 sleep packages with one of our sleep experts who can advise if this is something we can help you with. 

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Images by Estelle Thompson Photography

Company Name: The Daddy Sleep Consultant Ltd

Company Number: 13226982

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