The 4 month sleep regression also known as “the 4 month sleep shift” and “the 4 month wakeful period” is the transition your baby goes through from having baby sleep to sleep that resembles yours! This is the biggest change that your baby will ever experience in terms of sleep.
This sleep change generally occurs between 3 and 5 months which seems so young to have such a dramatic biological change occurring. Many families will finally begin to see a pattern emerging in their young baby’s day and then out of the blue their baby will begin to wake more frequently at night, seem wide awake for longer periods during the day, wake from naps after 30-45 minutes and wake up often during the early morning hours.
Although the most common term is sleep regression I do like to look at this as a sleep shift. It is a developmental milestone that your baby has reached and even though it seems like sleep goes down the drain there is a light at the end of the tunnel.
What is happening during this sleep shift?
Your baby is born with two classifications of sleep: REM Sleep also called “active” sleep and Non-REM sleep also called “quiet” sleep. These sleep patterns develop in utero and by the end of the 8th month of pregnancy both states are established. Your newborn will cycle through these two sleep stages throughout a sleep period. Your baby is most likely in REM (active) sleep when you notice them twitching, breathing irregularly, smiling and when you see their eyes moving beneath their eyelids. Non-REM (quiet) sleep is identified when your baby is breathing deeply and lying very still. REM and Non-REM sleep both make up about 50% of your newborns sleep patterns. Newborns usually fall into REM sleep first which is why the smiling and eye movement is what you first observe before they become limp.
4 Month Sleep Shift
Somewhere between 3 and 5 months your baby begins to experience biological changes to their sleep cycles. Many resources state different times of when it begins but all experts agree that it is between this period of 3 to 5 months. The changes occurring are:
Their body is having a strong surge of sleep hormone production. This means that the sleep hormone melatonin is now encouraging sleep habits. Prior to this your baby’s wake/sleep cycle was more so determined by their physical needs. This is why they would sleep, wake up to eat and be changed and then go back to sleep. Now that melatonin is affecting sleep on a higher level we want to help encourage melatonin production for sleep times!
Non-REM sleep is further dividing into 4 stages. As a newborn your baby only had 1 stage of Non-REM (quiet) sleep which resembled stage 3 (20-30 minute mark on chart) and so this made it so they could easily sleep anywhere such as a carseat, swing, crib, bassinet, in your arms or even in a crowded room.
This stage of sleep is now further dividing into 4 stages:
0-10 Minutes – Stage 1 of Non-REM Sleep.
10-20 Minutes – Stage 2 of Non-REM Sleep.
** Stages 1 and 2 are the lighter stages of sleep within the Deep Non-REM sleep. If you try to lie your baby down during one of these stages they will often wake up!
20-30 Minutes – Stage 3 of Non-REM Sleep.
30-40 Minutes – Stage 4 of Non-REM Sleep
45-60 Minutes – REM (light) Sleep.
** All of these times are approx.. Every baby is a little bit different but generally a babies sleep cycle is 45-60 minutes and so your baby may experience an extra minute or two in different cycle stages.
With the development of deep sleep stages partial awakenings begin to occur. These are periods of awakening that occur during each sleep cycle. These awakenings can either happen following deep sleep before entering into light sleep or they can occur following light sleep before entering into the next deep sleep cycle. If the awakenings occurs following Non-REM (deep) stages of sleep before REM (light) sleep then babies are often able to continue sleeping and just move around slightly. If the awakening occurs after the REM (light) cycle then they will be much more awake and so this will be when they call out to get you.
These awakenings tend to be what disrupts sleep the most in your young baby because they are not sure how to go back to sleep when they wake up. Prior to this developmental milestone they only woke up for a physical need of feeding, diaper change or comfort but now they are experiencing these awakenings even if they don’t need something. If they do not fall asleep at the beginning of the night on their own then this is when they will need you to help them fall back asleep. They are having this partial awakening for a number of different reasons but generally the reason that they call out to the parents is because they are not sure how to put themselves back to sleep. In most cases, however the child fell asleep at the beginning of the night will be what they need to go back to sleep at this awakening. This is what we refer to as sleep associations. Is your baby waking up at the end of each sleep cycle? If so, read my sleep associations blog here.
Your baby begins to enter stages of Non-REM sleep first versus REM sleep like when they were newborns. This makes It harder for us as parents to read them because they often look like they are in a “deep” sleep but now they are only in stage 1 or 2 of Non-REM sleep and so they will awaken easily when moved or put down.
During the transition the percentage of time your baby stays in each stage of sleep changes from 50/50 of REM (active, light) sleep and Non-REM (quiet, deep) to the majority of sleep being made up of Non-REM sleep in a 24 hour period.
Older Infant, Children and Adult Sleep
Following the sleep shift your babies sleep pattern will now be similar to yours. As they continue to get older their sleep cycles will extend from 45-60 minutes to closer to 90 minutes like an adults and this typically occurs around age 3-4. These changes are much more gradual and easier to adapt to than that of the big change they just experienced.
Sleep is now labeled a little different with REM sleep called “light” or “dream” sleep and Non-REM sleep called “deep” sleep. You still experience partial awakenings in your sleep cycles and so this is usually when families notice that even though the sleep regression has passed their baby is still waking frequently at night. Working on the habits that your baby uses at the beginning of the night to fall asleep can greatly improve night wakings because your baby will have new strategies on how to go back to sleep duirng the awakenings.
The complete phase of the sleep shift or regression is said to be over by 6 months (earlier in some babies). This is why I often recommend to start any type of sleep coaching strategies after this age when the sleep cycles are established and sorted out in their body. It is hard enough going through these big changes without adding sleep coaching on top of it! There are many things you can focus on during the regression so that you come out on the other side of the regression on a healthy foot.
How to get through the sleep shift/regression
Stick with your wake time windows. Your baby’s body is working hard at producing new hormones and creating sleep cycles and so we want to keep them rested. When a baby is overtired they are fussier, harder to put down and have greater difficulty responding to change.
Follow wake-times to allow for an early bedtime. As this sleep shift occurs your baby’s schedule is going to move earlier. You may notice them waking up earlier and therefore going to bed earlier.
Have the last nap of the day ending by 5:00 p.m. This allows for bedtime to happen at an appropriate time.
Set up the room environment so that it is helping the sleep hormones encourage healthy sleep cycles. Having a dark room and using white noise are two ways that can help this process.
Work on having consistency for sleep location. Everyone loves having their own safe, sleep space. This is why you prefer to sleep in your own bed!! It doesn’t matter where the sleep space is but work on having naps and bedtime sleep happening in this location so your baby can develop a positive feeling towards their sleep space.
Focus on consistent routines. This is a big one. As your baby is adjusting biologically to the changes going on you will need to follow your routines exactly so the body knows what to do. Your routines are what signal to the body that it is going to be sleeping and so if we want to encourage sleep hormones to begin your baby needs to recognize the routine.
Be patient! This is a hard phase. Even I, a sleep “expert,” had a very hard time at this sleep shift. It seemed like I was doing everything right but sleep was still unpredictable, inconsistent and frustrating! You can’t change that their body is going through this change and so instead we have to just acknowledge it is happening and try and keep everything as consistent as we can. By working on healthy sleep foundations you can come out on the other side of the regression with some strong healthy habits in place that will lead you in the right direction. This way if you still need some sleep coaching direction you will have many things done already.
This age can be tough but there are MANY things you can work on to make improvements with sleep in your home. Join me for an upcoming local OR online sleep course to get everyone in your family sleeping better!! Click HERE to learn more!
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"I just wanted to write to all the parents that are desperately looking for a change in their little ones sleep habits but do not know where to start. I reached out to Hailee around February, very skeptical that someone who has never met my baby could actually make a change in her sleep. Little did I know that this would be the best investment I’d ever made, on Hailee, into my baby, and into my own downtime with my loved one."
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