The 4-month sleep regression is undeniably one of the most discussed topics in every moms’ forum. With so many people throwing out random explanations for why a baby is not sleeping well (i.e. baby has gas, is teething, has a strange form of sleep regression), I feel it is time to shed some light in this whole thing called the 4-month sleep regression.  

The 4-month sleep regression is attributed to the fact that key developmental changes occur at that specific period in your baby’s life; changes that affect sleep. However, if you think about it, a baby also undergoes significant changes at nine months and 18 months too. So, what is so special about 4 months that is not found in other milestone ages? Truth be told, there is a bit of science hiding behind the 4-month sleep regression. Today, we will find out more about this science, along with ways to help your baby get over it while also minimising the distress the 4-month regression may cause. Remember that where there is a baby-related problem, there is always a solution!  

Understanding Newborn Sleep Cycle 

Around the three to four-month mark, the baby experiences a dramatic change in its sleep pattern. But, let’s take first things first. Newborn babies have a sleep cycle that consists of only 2 phases (as opposed to adults that have 4 sleep stages):   

  • The Stage Three Sleep – Also known as deep sleep or slow wave sleep, it is the kind of sleep where there is almost no movement going on. You can tell that your baby is in deep sleep (just try to pick up their arm and drop it – it will fall like dead weight!).   
  • REM (Rapid Eye Movement) Sleep – The baby is really active with lots of movement going on (i.e. twitching, legs crunch up, face makes all kinds of movements, arms are shooting out, etc.).  

Both sleep stages are super important for the baby’s development. For instance, deep sleep is when our bodies do a lot of restorative work, immune system building and cell repair. Imagine how crucial this stage is for newborn babies, given that their bodies are growing rapidly day by day, they are exposed to so many germs from the environment, and that there is so much stimulation coming in on a daily basis. They just need to do much deep sleep because they have quite a lot to catch up! 

REM sleep, on the other hand, has a lot to do with memory, storage, stimulating all five senses, neural connections, and more. Considering the fact that a newborn baby’s brain receives a ton of stimuli from the moment they open their eyes – information that needs to be properly organised and stored –  they need to figure out what to do with all that five-sense stimulation. All that happens during REM sleep.  

One of the most miraculous mechanisms of the human body is its ability to enter a stage of deep relaxation during REM sleep so all the necessary work is done. This is why we (adults) go into muscular paralysis when we go into REM sleep, which prevents us from doing things like getting out of bed or acting out in our dreams. Skipping this phase is a serious sleep disorder – research has shown that those who lack REM sleep tend to become physical violent. Newborn babies do not have that mechanism developed until they are 3 or 4 months old. This is why they seem active and restless when in REM sleep (nothing to worry about, though).  

What is also different is the way a newborn baby’s sleep is organised, compared to that of an adult, which is why you find it so difficult to cope with the baby’s sleep pattern. Your sleep organisation is the complete opposite of the newborn’s (a newborn is usually on a 24-hour clock of periods of sleep followed by periods of awake).   

All that shifts around the 3 to 4-month mark, when babies leave the 2-phase sleep and go into a 4-stage sleep cycle. For some babies, this can be a real challenge.  

Reason Why a Baby Goes Through the 4-Month Sleep Regression

A significant reorganisation of sleep occurs in your baby’s life as they cycle through the 4 phases roughly every 90 minutes. The two additional stages of sleep they are now introduced to are: 

Phase 1 – When you lie down to bed, get into your favourite position, and are beginning to fall asleep. You are fading in and then out and are not yet fully aware that you are truly asleep. You slide into sleep and are coming back into consciousness for 10-15 minutes.  

Phase 2 – Considered the first true sleep stage, it is light, yet quite deep. It is easy to awake and be consciously aware that you were indeed sleeping and somebody woke you up.  

Then comes deep sleep, followed by a little bit of stage 2 again and then REM sleep. And that goes on throughout the night. The newborn that goes out of the newborn phase and into an older baby stage has to add these two new phases into their sleep cycle and reorganise the amount of time they spend in each stage. When newborns, 50% of their total sleep time goes to deep sleep and the rest 50% in REM. Now, they have to drop REM and deep sleep to around 25% each and add stages 1 and 2 mentioned above, which is a lot of work for their brains and bodies to process. For some babies, this is a bit of a struggle; they just need more time to develop milestones. That is the reason why some babies go through the 4-month sleep regression.  

Why Sleep Regression Becomes a Problem 

First of all, there is more light sleep now through the night (even REM sleep is light). This means that they can be more easily woken. If, for instance, a dog barks, the floor board squeaks a bit louder, a siren rings and they are in stage one, it can wake them up.  

Secondly, babies at the 4 mark are also having more naturally occurring wake ups. When we cycle through the 4 sleep stages every 90 minutes, we usually come to the surface of sleep during the transition from one sleep stage to another. Sometimes, this causes several partial awakenings during the night (could be brief wake ups that you don’t even recall in the morning or a full blown wake up that make you get out of bed). This is normal for us and babies alike, who can have a full blown wake up if some things are different (i.e. they were breastfeeding and found themselves awake in the middle of the night in their crib). You know what comes next. They will cry for you, and you will need to come in and help them.  

A third problem is that the baby has a strong sleep-prop. This means that the baby starts convincing themselves that they need something to help them sleep (i.e. pacifiers, rocking to sleep, nursing to sleep, etc.). At 4 months old, their awareness is heightened (i.e. recognise you, learn things, smile at you, etc.). Being more cognitive aware, babies start realising that you are not rocking them anymore or breast-feeding anymore, which can cause an angry wake up and a hard time going back to sleep again. They may want to, but they do not know how.  

How to Help Your Baby With the Transition 

White noise to muffle external sounds that may annoy/awaken the baby and ensuring the room the baby sleeps is dark during sleep hours definitely help the baby adapt to the new sleep cycle.  

Having the baby on a bedtime routine is very important too. It is a “signal” for the brain and body to start going from day to night. We all have a bedtime routine both before and when we get into bed, which is the same every night (i.e. turn into our favourite sleeping position, get our water, etc.) that help us relax, keep our anxiety levels low, and eventually fall asleep. Likewise, babies need a bedtime routine of around 4 or 5 steps (i.e. have a bath, slip on the pyjamas, feed, read a bedtime story); steps that should be the same every day so they baby understands that they are going to sleep shortly.  

What is also crucial is that the baby goes to bed early enough (I suggest tucking them in at around 7 pm) and make sure the baby is not too tired before bedtime. It is your baby’s worst enemy and it is easy to understand why. An overtired baby often cries too hard, is over-restless, they don’t know what they want, nothing seems to please them and they get cranky. Don’t wait for the fussiness to emerge. Instead, catch them when they are still calm and happy and put them down to bed before they become too tired to sleep.  

Now, if your baby finds it very difficult to fall asleep without your assistance or something that they believe will help them fall asleep (the prop), it is paramount to help them learn some independent sleep skills. Finally, remember that there will be regressions; that is normal. So many changes occur in their bodies that could affect their sleep patterns! Just stay consistent with bedtime routine and it will pass sooner than you may think!