Baby Sleep Regressions: What Causes Them and How to Handle Them

developmental milestones sleep patterns sleep regressions sleep stages Nov 02, 2021

It can be confusing when your baby who is typically a great sleeper begins waking multiple times per night, without warning! The term “regression” is used to describe this, however, it’s important to remember that not everything is a true “regression.”  

The most common sleep regression for a baby to experience is the “4-month regression;” as somewhere between 3-5 months, there is a huge shift for babies, developmentally! Not only are they becoming more aware of their surroundings, but they are also transitioning from 2 sleep stages to 4. [1] 

Oftentimes, babies also have changes in their sleep patterns due to something exciting, like a new milestone they are hitting! 

When these sleep disturbances happen, it’s important not to rush to “fix” anything by introducing old or new associations that your baby didn’t previously need. If your baby has already learned how to fall asleep and get back to sleep on their own, then these “regressions” are a minor hiccup that will pass and things will go back to normal soon. 

What Causes Baby Sleep Regressions?

Throughout the first few years of life, sleep patterns are ever-changing and vary person-to-person. [2] This means that all babies are different and the timing of these “regressions” may be different for each one! In fact, some babies may not be affected by regressions at all (even though all babies will shift from 2-4 stages of sleep), so don’t stress in anticipation waiting for any of these milestones to disturb your baby’s sleep. 

1. Your Baby is Becoming More Cognitively Aware

When your baby is becoming more cognitively aware, it actually means that their brain is changing! They’ll start to notice objects more easily and be more likely to become overstimulated by things like a shadow on the wall or a mobile over their head. Or maybe your neighbor has a barking dog that they used to be able to sleep through, but now that same dog barking can easily wake them out of a sleep cycle.

This could also mean that if your baby has a sleep association, they could have a really hard time falling back to sleep without it.  If you want to know more about sleep associations, follow me on Instagram!

2. The 4 Stages of Sleep Begin to Develop 

Your baby’s sleep cycles also change because of the maturing of their circadian rhythm. Around 2-3 months, your baby’s circadian rhythm will start to develop, leading to the development of sleep consolidation. This results in longer awake times during the day and longer periods of sleep at night! [3] 

As a newborn, your baby’s sleep is distributed evenly throughout day and night, and it’s normal for them to sleep as much as 16-18 hours during the day. This sleep is discontinuous, though and only lasts 2.5 to 4 hours at a time. They also only go through 1 or 2 sleep cycles, with the onset of sleep occurring at the REM (rapid eye movement) stage. [4] 

Between 3-5 months, your baby’s sleep cycles become more regular and sleep onset switches from REM sleep to NREM (non-rapid eye movement) sleep. The REM sleep stage that your newborn spent the most time in will decrease and shift to the end of their sleep cycles. [5]

NREM sleep consists of 3 sleep stages: [6]

  • Stage 1: Your baby is in their lightest stage of sleep during this stage (or drowsy). 50% of alpha waves are replaced with low-amplitude mixed-frequency (LAMF) activity.  Your baby is easily awakened during this stage of sleep. 
  • Stage 2: This is a deeper sleep than stage 1. Sleep spindles & K-complexes are present and your baby will begin to drift into stage 3.
  • Stage 3: As the most difficult stage of sleep for your baby to awaken from, this stage is the deepest & most restorative stage of sleep. The body repairs and regrows tissues, builds bone and muscle, and the immune system strengthens!⠀

After the 3 stages of NREM sleep, the REM stage of sleep occurs.  This is when dreaming takes place, and information and memory storage happen.

Why is understanding this transition important? As babies shift into more stages of light sleep, they're more easily awakened, meaning more night wakings or 1-cycle naps. If they don't know how to get back to sleep independently, they're going to need your help after each waking.⠀⠀⠀

To help with this, I recommend putting your baby down AWAKE, so they learn HOW to fall asleep without being fed to sleep, rocked, shushed, etc. When your baby knows how to fall asleep independently, they’ll have a greater chance of sailing through this developmental regression without too many disruptions.  ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

If your baby is between 0-3 months and you’re looking to prep for sleep before they hit the regression, check out my Newborn Sleep BFF Guide. If your baby is between 4-18 months and needs some extra support learning how to do this, my Mastering Baby Sleep 101 Sleep Training Guide can help. 

3. Developmental Milestones

Developmental milestones for your baby are both cognitive and physical. Cognitive milestones could mean that they are experiencing separation anxiety, they’re having a language burst, or they have increased awareness (which can sometimes lead to fears). 

Physical milestones relate to when your baby learns a new gross/fine motor skill.  This could be rolling, sitting up, crawling, standing, or walking. When your baby learns these new skills, it’s very common for them to start practicing them at night. Obviously, that’s not the ideal time for us parents! Or sometimes, they can get “stuck” in a position and need your help getting comfortable again. A common example of this is when a baby learns to roll from their back to their tummy but hasn’t quite learned how to roll back yet! 

How to Handle Baby Sleep Regressions 

While it’s important to know why these sleep regressions happen; even more important to know is HOW you should handle them. These regressions that are based on developmental milestones are short-lived, so remember these two important tips for handling these regressions:

  1. Stay consistent: Since these sleep disturbances won’t last long, it’s important to not start implementing any new habits that your baby didn’t previously rely on for sleep.  If your baby typically sleeps through the night without a night feeding, don’t add in a feeding during this short stint of night wakings, or it will likely become a new sleep association that your baby now comes to rely on. 
  2. Practice: If the developmental milestone your baby is going through is physical, the most important thing to do is to practice their newly learned skill as much as you possibly can during the day so that your baby can master it as quickly as possible and spend their nights sleeping and resting! Cognitive milestones aren’t as easy to practice, so just wait them out and the regression will pass on its own with time. Check out this blog for some tips on how to help your baby get back to sleeping through the night as quickly as possible!

These sleep regressions can be tough if sleep associations that were once working for your baby are now relied on and needed every time they have an unintended waking, or they’re just not working at all anymore. For example, maybe you used to be able to rock your baby to sleep and transfer them to their crib without them waking up, but now they wake up upon every transfer and you’re back to square one. This can be exhausting and frustrating.

This is why it’s helpful to practice independent sleep skills with your little one! When we are consistent and practice often, giving our children as much opportunity to fall asleep independently as possible, they are able to learn to fall asleep on their own, as well as get back to sleep between cycles on their own. Keep in mind, this is easier to practice and catch onto when babies are under 4 months old. Once babies are more cognitively aware, it is common for a more regimented independent sleep process, like a specific sleep training plan to work more effectively. 

Do you have to sleep train your baby? Of course not! This is a personal choice and I always recommend doing your research to find the best and more effective method for your baby’s sleep. 

If you find yourself still struggling with your little one’s sleep, please know that you are not alone and that I am here to help. Download one of my comprehensive sleep guides or schedule a call with me for some personalized support. 


[1] [3] [4] [5] [6]   



Need help transforming your child's sleep? Check out my sleep offerings for children 0-3 years old!


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