The 4 Month Sleep “Regression”

We hear it all the time. The 4 month sleep regression. Parents are often baffled at the fact that their child slept wonderfully from birth until 4 months and then it seems that it has turned into a train wreck. Baby will begin waking from naps after 30-50 minutes, staying awake for longer periods during the day and is likely to experience more night wakings. There is a biological reason for all of this.

From newborn - 4 months (ish), a baby will immediately enter REM sleep (light sleep)once they fall asleep. This changes once they reach 3 months of age when they will enter non-REM first and this pattern will continue for the rest of their lives. At this age, we as Sleep Consultants, say sleep becomes more adult-like. This is a wonderful thing, which is why I disagree with the term ‘regression’.

I’m going to give you a quick run down of what your child’s sleep cycles look like in a typical night.

A child 4 months + will have their deepest sleep, non-REM, during the first half of the night. After these deep sleep cycles, the child will bounce back and forth between lighter periods of non-REM and more intense periods of REM sleep. This period of sleep lasts approximately 4 hours and it is during these transitions that your child may start to experience sleep issues. Because sleep isn’t as deep in the middle of the night as it is in the beginning, and because your child will experience more wakings, this is when a child will likely rely on Mom or Dad to help get them back to sleep. Four months is the perfect age to start to let Baby learn how to self soothe.

Once a child is through these middle of the night sleep cycles, they will then transition between deep non-REM and REM sleep for the remainder of the night. Have you noticed that it’s easier for you to wake in the middle of the night compared to a few hours after you fall asleep for the night or when your alarm goes off in the morning? It’s because you are in a deep non-REM sleep stage. Same thing.

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Baby’s circadian rhythms begin to form around this age, meaning they will thrive on routines and schedules. Baby won’t nap ‘on the go’ as easily and will do best having their naps at home, in their dark bedroom. I know it’s hard to be home for every nap, especially when they are happening 3-4 times a day. But if your baby could talk, they would be thanking you for respecting their sleep needs!

Another change that happens around this age is the 4-3 nap transition, and overtiredness is bound to happen (as it is with all nap transitions). Overtiredness is a major reason why Baby is now experiencing more night wakings. An early bedtime is key during this nap transition as it will help Baby catch up on that lost sleep from dropping the 4th nap. During the first 4 months, Baby had a combination of short and long naps. Now that Baby is maturing; these short naps aren’t providing enough restorative value, which in turn is leading Baby to be overtired. Sounds fun, right?

Baby will be settling into a solid 3 nap schedule around this age. The morning nap is established when it becomes consolidated (no waking and crying off and on) and baby wakes up happy and calm. The morning nap is mentally restorative while the afternoon nap is physically restorative. The 3rd, or 4th (for babies still needing 4 naps) nap doesn’t have much restorative value. It’s basically used as a ‘carry over’ to get Baby to bedtime without becoming overtired.

This is also the age that babies learn to roll, which starts by being able to roll one way. Until Baby learns to roll both ways, they will get stuck on their tummies. Make sure you practice rolling like crazy - put Baby on her tummy in the morning after feeding and diaper change and practice, practice, practice! It’s a short phase that ALL babies go through. If Baby has been swaddled up to this point, it’s time to get rid of the swaddle and switch to a sleep sack.

As you can see, there are many things going on in Baby’s life and naturally, sleep will be affected by it all. So unless you are OK with doing the paci dance or being a human pacifier all night long, I suggest implementing some healthy sleep habits and being respectful of Baby’s sleep needs.

Ferber, Richard. (2006). Solve your child’s sleep problems. New York, NY: Fireside.


Lindsey Hennigar is founder of The Sleep Ranch and a Certified Infant and Child Sleep Consultant through the Family Sleep Institute. She works 1:1 with exhausted families to get them the healthy, restorative sleep they need. Your child can LOVE sleep!