The Dreaded Four-Month Sleep Regression

funny portrait of adorable little baby in glasses with old book (thinking expression)

As a sleep consultant, the term “regression” comes up frequently.  Essentially, if a baby is not sleeping well for a few nights, the “R” word can get dropped.  You may have even heard about an eight-month regression, a nine-month regression, a one-year regression, as well as teething regressions, growth spurt regressions, etc.  Some see these as simple hiccups caused by extenuating circumstances.

The four-month-regression is the only actual regression or “progression” and it’s permanent.  

What is the four-month sleep regression?

The simple answer:  It is when babies switch from two stages of sleep to four stages of sleep.

Sleep is made up of four different stages which make up the “sleep cycle” that we go through several times per night:

Stage 1 is that initial stage we are all familiar with where you can just feel yourself drifting off, but don’t really feel like you have fallen asleep. Anyone who has ever seen their partner nodding off while watching a movie, told them to go to bed, and gotten the canned response of, “I wasn’t sleeping!” knows exactly what this looks like.

Stage 2, which is considered the first “true sleep” stage. This is where people tend to realize, once woken up, that they actually were sleeping. For anyone taking a “power nap,” this is as deep as you want to go, or else you’re going to wake up groggy.

Stage 3 is deep and regenerative. Also known as “slow wave” sleep, this is where the body starts repairing and rejuvenating the immune system, muscles tissue, energy stores, and sparks growth and development.

Stage 4 is REM (rapid eye movement) sleep. This is where the brain starts to kick in and consolidates information and memories from the day before. It’s also the stage where we do most of our dreaming.

Once we’ve gone through all of the stages, we either wake up or come close to waking up, and then start over again until the alarm goes off.

Newborns, on the other hand, only go through two cycles of sleep:  REM sleep and Stage 3, spending 50% of their time in each cycle.  When this change takes place, around the four month mark, baby moves from 50% REM sleep, or lighter sleep, to 25% in order to make room for stages 1 and 2 of sleep.  Although REM sleep is light, it is not as light as the first two stages they are getting used to and with more time spent in lighter sleep, the chance baby will wake up becomes higher.  

That’s not to say we want to prevent or avoid baby from waking up.  We all wake up throughout the night naturally as we cycle in and out of different stages of sleep.  The difference between adults, or babies that have independent sleep skills, is when we wake up, we know how to get ourselves back to sleep and realize it’s not morning yet.  Most of the time, we don’t even remember waking up at all!  

Around the 3-5 month age range, sleep becomes reorganized, as babies embrace the 4-stage method of sleep that will continue into their adult life. If you had a newborn baby that was falling asleep quickly at bedtime and giving you long stretches at night but has suddenly changed around four months, this could be due to the change in sleep cycles.  If your newborn could easily fall asleep by nursing, a bottle, pacifier, or rocking to sleep, and now it is taking longer to fall asleep at bedtime with multiple wake ups throughout the night, the “four-month sleep regression” could be to blame.  

Now that I understand what the four-month sleep regression is, how do I get my baby sleeping well again (or maybe they never slept well, but I am ready for a change!)?!

A major contributor to the change in sleep during this time is baby relying on sleep props in order to fall asleep initially and get back to sleep in the middle of the night and nap time.  A sleep prop is anything external baby uses to fall asleep.  The most common sleep props are nursing, bottle, rocking, and pacifier.  We use these props because many newborns do not have the self-soothing skills.  They could also “get away with it” before the four-month regression hit because REM was their first stage of sleep before. 

Now that baby is spending more time in light sleep and has a higher probability of waking up, this can become a bigger issue.  These sleep props or sleep associations are sneaky because although they can be helpful in getting your baby to sleep initially, the absence of them when baby wakes up means that baby will have trouble getting back to sleep throughout the night without them.  This causes the fight-or-flight, crying and adrenaline when baby is waking up every hour or few hours, creating a nightmarish situation for parents.

I have also seen many clients who lay baby down in the crib after the bedtime routine, only to have them wake up immediately, needing to restart the bedtime routine again and again, causing a much later bedtime than needed.  This causes an increase in stress levels for the baby and parents.  Once baby does fall asleep, they are sleeping in shorter stretches at night because when they are cycling in and out of the four stages of sleep, they only know how to fall back to sleep with the sleep prop(s) used at bedtime.

The good news is, this is not actually a regression.  A regression is defined as “reversion to an earlier mental or behavioral level,” which is the opposite of what babies at this age experience.  A better title would be the “Four Month Sleep Progression.”

Another solution is to keep baby’s room as dark as possible.  Contrary to what we may believe, babies are not afraid of the dark.  They are, however, responsive to light.  Light alerts the brain that it is time to be active and awake.  The brain secretes hormones accordingly, so we want to keep the nursery pitch black for bedtime and during naps.

Another sleep interrupter is noise.  It could be the garbage truck in the morning, the dog warning you about squirrels running around the yard, or a caregiver getting ready for work in the morning.  With babies spending more time in lighter sleep, they can be easily startled by noise waking them up.  This is why I recommend using a white noise machine for night and day sleep.

Is white noise considered a sleep prop?  It is a prop, but it does not require any winding, resetting, reinserting or parental presence.  It is just there and can be turned on when baby is sleeping, so it is not a prop that you need to avoid.  

Having a consistent bedtime routine is an essential component to getting baby sleeping well.  The routine should contain about 4-5 steps and avoid feeding baby to sleep or drowsiness during the routine.  Otherwise, you risk baby associating the feed with sleep which can cause issues throughout the night and for naps.

Keeping the feed towards the beginning of the routine, with the PJ’s, stories and songs towards the end can be helpful.  The total amount of time should be around 20-30 minutes long, and baby should go into the crib while they are still awake.

If you are noticing baby seems fussy and tired during the bedtime routine, you may have waited too long to put them to sleep.  Four-month-olds should have about a 2-hour awake window before they are ready to sleep again.  An ideal bedtime would be between 7-8 pm.

As your baby grows, there will be actual regressions due to travel, illness, and developmental milestones that can cause a few bad nights in a row.  But when it comes to the four-month “progression”, this is a one-time thing.  Once your baby goes through this, they will have officially moved into the sleep cycle that they will essentially be following for the rest of their lives.  

If you take the opportunity to teach your baby the skills they need to string those sleep cycles together, on their own, without sleep props, you will be giving them the gift of sleep they will enjoy for the rest of their lives.

Of course, taking away sleep props is easier said than done. Some babies take well to the change, while others have a harder time.  If your baby falls in the latter category, I am happy to help you teach your baby how to fall asleep independently and get the developmentally age-appropriate sleep they need.  I offer 1-1 support to help you reach your baby’s sleep goals, so everyone will feel more rested:


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