The '4 month sleep regression' has celebrity status in my sleep world.  I hear this phrase almost every single day; from an exhausted mom of a 5 month old, wondering why her baby's sleep has gone downhill in the last month, to parents of a toddler who say that "their baby has never slept well since 4 months of age", or even from a mom of a 3 month old, worried about the upcoming "regression".  I am here to help you realize what goes on around 4 months, and how we can prevent a true 'regression' from occurring.

What is a sleep regression?

A sleep regression is thought to occur when a baby who is normally sleeping well begins to wake frequently at night and/or fights/refuses naps.  These regressions seem to come out of nowhere and can last indefinitely.  There is thought to be a regression around 3/4 months, 9 months, and 18 months.  Not at all coincidentally, we can see that all of these 'regressions' occur around the same time as nap transitions (the 4-3 nap transition around 4 months, the 3-2 nap transition around 9 months, and the 2-1 nap transition around 18 months).  In my opinion, these regressions are really just our babies' sleep needs changing and parents are not prepared to handle these changes properly, thus leading to baby becoming overtired.  You know by now that an overtired baby will wake frequently at night and/or fight/refuse naps so - voila!- a 'sleep regression' is born.

So what causes the '4 month sleep regression'?

Four months is a very busy time for babies.  There is a lot that happens with our children's sleep at this age.  Four months is the time where a baby's sleep becomes more like an adult's.  I won't bore you with the details about how this happens, but it's important to know a little bit about why some of the things that you were previously doing (i.e. rocking/nursing to sleep) seem to quit working at four months of age.
Previous to 4 months, when a baby would fall asleep, they would immediately enter into a deeper non-REM sleep.  This is why you would have been able to rock/nurse your baby to sleep and then put them down without them waking up.  As well, they were likely able to sleep just about anywhere; in the car seat while grocery shopping, in the stroller while you took a walk, or in the carrier while you did your household errands.  Around 4 months, as sleep becomes more 'adult-like', your baby will not enter immediately into that non-REM deep sleep stage as soon as they fall asleep.  Instead, they will first enter into a lighter sleep stage of non-REM.  If we are nursing/rocking baby to sleep, and then try to put her down....POP!  She is up, wide awake, and ready to go.  Then the process of helping her to fall asleep is repeated again and again, only causing baby to become overtired.

Four months is also the age where some babies begin to roll.  This means that the swaddle is no longer safe to use.  The downside to this is that most babies at this age still have some, if not all, of their startle reflex (which is what we are trying to prevent with the swaddle).  Simply unswaddling our babies and moving straight to a sleepsack will often cause baby to begin waking themselves up at night or start to have difficulty falling asleep/staying asleep for naps.  This is why I am such a fan of the Baby Merlin's Magic Sleepsuit.  It is a fantastic tool for babies who aren't able to be swaddled but just aren't ready for a sleepsack quite yet.

At four months, we begin to see sleep patterns mature and nightsleep consolidate.  This means that your baby who was previously sleeping in until 7:00 or 8:00am may begin to shift his natural wake-up time earlier, to around 6:00-7:00am.  This then means that we need to begin shifting the bedtime earlier as well to account for this.  It is a very common misconception that putting your baby to bed later will help them to sleep in - it is the exact opposite that is true.  Putting your baby to bed later in hopes that they will start to sleep in will only backfire and lead to an overtired baby who will in turn wake up even earlier.  This early to bed, early to rise pattern is here to stay and trying to fight it is going against baby's natural sleep rhythms.  Check out my blog post here to find out if your baby's bedtime is too late for his/her age.

As I touched on briefly, 3-5 months is the average age that the 4-3 nap transition occurs.  The longer wakeful periods begin to push baby's naps later therefore making bedtime too late as well.  Remember, around this age we do not want any nap occurring later than 4:30-5:00pm.  If you are finding that the 4th nap is happening much past this time - it is time to drop that nap and move bedtime earlier.  That is the key!  Bedtime needs to move earlier to account for that entire sleep period that's been eliminated.  

For more information on newborn sleep, check out my Comprehensive Newborn Sleep Guide here!

As I mentioned above, at four months of age it becomes increasingly difficult for baby to fall asleep on-the-go.  Where a newborn could sleep through just about anything, babies at four months are becoming increasingly aware of their surroundings.  Many parents find it inconvenient to be home every 1.5 hours to get their baby the rest that she needs but if we keep trying to push babies to fit into our schedules, they are going to re-pay us by waking frequently at night.  In addition to this increasing awareness making it difficult for babies to nap on-the-go, it also means that your previous methods of soothing baby to sleep (i.e. nursing/rocking/bouncing/etc.) in fact become the opposite of soothing - they become too stimulating for baby.  If you are finding that you are spending hours using all of your tricks to get baby to sleep, she might be telling you that she needs to be falling asleep more on her own.

So what can we do to avoid this 'regression'?

It is all about recognizing our baby's changing needs and having a flexible schedule that is in sync with our child's natural sleep rhythm.  We as parents may think that because we started one way (by always nursing to sleep, by rocking to sleep, by holding baby for all sleep) that this is the way that baby will always need to sleep.  This is definitely not the case!  When these things stop working we need to switch it up and find something new to help our babies get the sleep they need.  Sometimes, a little bit of sleep coaching is necessary to break the cycle of overtiredness and to reinforce healthy sleep habits but at such a young age we are able to use super gentle methods and they unlearn these 'bad' habits very quickly.  But just remember, no amount of sleep coaching will work on a baby who is overtired and whose schedule is not meeting their needs, so do not be quick to 'sleep train' your child unless you are prepared to make sure baby is napping enough during the day and at the right times, and is in bed at night with an age-appropriate bedtime.  Otherwise, this sleep training will only lead to even more overtiredness and unnecessary crying.
We also always need to be sure that we have an age-appropriate schedule for baby that meets his needs.  Check out my blog post here for what a 'typical day' in the life of a 4 month old should look like.  While it is very true that a baby rarely fits into our schedule, the time that is spent in 'babyhood' is so very short, and besides food, there is nothing else that is more important to a little baby than sleep.

While it would be nice if this '4 month sleep regression' was only a phase that will disappear in time, unfortunately, it is not.  It is more often a product of poor sleep habits and an inappropriate schedule.  As long as we are aware of all the developmental points above and are prepared to adapt to meet our baby's new needs, we will be able to dodge this dreaded regression and continue to enjoy the benefits of a good night's sleep.