What Really Happens to Sleep At Four Months?

Baby’s sleep goes through a huge change around 4 months, but this can actually occur at 3 months or 5 months as well. This change is typically described as the 4 month sleep regression, it’s much feared amongst parents as it can cause havoc with your child’s sleep. Even a previously ‘good’ sleeper can suddenly start cat napping and waking frequently at night.
When you understand what causes it you can better understand how to deal with it, it isn’t like other sleep regressions that will go away after a couple of weeks, it can stay for many weeks, sometimes months!
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The 4 month sleep regression is actually a progression in babies sleep and their neurological development. Prior to this your baby’s new-born sleep phases were deeper and they more easily drifted from one cycle to another. Once they hit this milestone around 4 months, they now have lighter phases of sleep and rouse fully in-between sleep cycles.
The length of a sleep cycle is 40 minutes during the day and 2 hours at night, which means they will be waking this frequently at night and catnapping during the day.
Adults also have sleep cycles and we wake in between them, we however know how to go back to sleep and do so easily without remembering the next day. This is what you’ll now need to teach your baby to do.



The progression in sleep is biological and so will happen to all babies, some of them however aren’t as affected as other babies. This can be temperament but also because sometimes without even realising it, the parents have implemented healthy sleep habits before they hit this milestone.
These healthy sleep habits are things like a dark room, white noise and swaddle. As well as trying to put baby down in their own bed for some sleeps. Not relying on too many associations and assistance to get to sleep by the time they are 4 months will make this process easier as well.


If your baby is struggling with overtiredness then it will be harder for them to settle and you’ll be fighting a bit of a losing battle. To keep on top of overtiredness try and ensure that your little one has the right amount of sleep for their age.
To do this it’s useful to watch their awake windows, don't have a clue about awake windows? You can learn more here.


Don’t rush in, give them the chance to settle themselves. If we rush in before they have even woken up properly they will never learn the skill of putting themselves back to sleep and sometimes we’re assisting when they don’t even need it.
If you’re assisting to sleep you’ll need to stop and teach self-settling. Find a method that you’re comfortable with and that suits the temperament of your child, this may be in the room, out the room, using touch or not. It really does depend on what works for you as a family.
Be consistent and use that to teach them to settle themselves and re-settle. It can take 2 weeks but if you’re consistent and follow through you’ll see changes with your baby quickly sleeping longer chunks at night and learning to link those day sleep cycles past 40 minutes.
If they are having multiple feeds but of a healthy weight and thriving, drop down to 2 feeds one being around 10/11pm (can be a dream feed) and one around 2/3am. Use your settling method in-between those wakes to get them back to sleep.
4 months is a great age to teach this skill, they are now biologically ready and it will help with avoiding the repercussions of the later regressions down the line when they turn 8/12/18 months. Teaching them this skill now instead of waiting until they are a toddler is much easier.


This progression in your babies sleep will see them waking every sleep cycle, looking for what it was that put them to sleep in the first place. If you're using lots of sleep associations and assistance such as rocking, holding, feeding which worked in the newborn days you will now see your baby wake every 40 minutes during the day and 2 hours at night for this now.
In order to move past these frequent wake ups and unsettled behaviour, firstly remove sleep associations then ensure you follow age appropriate awake windows so your baby is getting the day sleep they need.
After that you need to teach them to self-settle by picking a suitable method and being consistent with it for 2 weeks. Once they learn to put themselves to sleep at the start of the night they will quickly learn to put themselves back to sleep when they wake in-between sleep cycles.
I have many clients coming to me at the 8 month mark having never fully got past the disruption from the 4 months sleep regression. Don't struggle on for that long, these excessive wakes are not sustainable, if you want some support then reach out here.
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