Sleep Regression at Four Months: Myth or Reality?

Today we discuss the myth of the 4-Month Sleep Regression.

A mom I consulted with recently told me a story that might sound familiar to you:

She came to me because her healthy 5-month old boy had slept great until about 3 1/2 months of age. Then he’d become incredibly cranky around 11 PM. He’d nurse fine, fuss for a few minutes, and then fall asleep for about 2 hours when he’d wake up again and the process would repeat every two hours throughout the night. She asked me if the baby were going through a sleep regression.

What is a Sleep Regression, Really?


I asked a few more questions and we determined that the baby was not ill – he’d just been to the pediatrician and he was gaining weight and developing normally. It also appeared that he was not teething yet. So it appeared that this was a normal sleep pattern that was occurring. Not a sleep regression, but a progression – that is to say a progression in the baby’s normal development! (Props to Pinky McKay for providing me with the perfect word to counterbalance “regression”) There are many such stages of infant development when sleep tends to go a little freaky.  The one at four months is merely the first. We can only speculate as to why these sleep disruptions occur. The truth is we really just don’t know why they happen.

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It turns out that at around four months, your baby is achieving through some very significant developmental milestones, all of which impact her sleep pattern.

Sleep Stages

sleep regression

The first has to do with what we call the architecture of baby sleep. Prior to about four months, baby sleep can be divided into essentially two parts: wide awake and deeply asleep. Starting at around four months, babies start to develop more mature sleep architecture.  They start to develop all four of the levels of sleep that we can measure with an EEG (Stage 1, 2, 3, 4, and REM). And when they sleep, they cycle through these levels much the way we do. An entire cycle lasts about 90 minutes to 2 hours, just the amount of time your baby is sleeping until waking up again! Again, we can’t say for sure why this leads to so many night-time awakenings, but we have a pretty good idea that it has something to do with this important milestone.

Something to do with Naps, Too?

sleep regression

Some experts suggest that the changes you’re seeing at around four months have to do with the baby’s changing napping habits. The theory is that the baby at around four months is in the process of dropping one of her naps, usually from 4-3.  Whereas this is true, it may not be related to the sleep problem you’re having now.  You’re probably in the process of feeling out when the baby needs to nap and when she wants to stay awake during the day.  Hopefully she’s still napping a lot.  If not, I discuss ways of troubleshooting this in a previous post.

How To Manage the 4-Month Sleep Progression

  • You can be reassured that the baby is perfectly fine and will pass through this phase in few weeks.
  • If the baby seems in any way ill, especially if she’s running a fever, this might be something to check with the pediatrician. Incidentally, swatting at ears is most often a sign of teething, not an ear infection.
  • Try to remain as consistent as possible in the daily routine. Consistency and sleep go very well together.
  • At the same time, follow the baby’s cues.  If she is “telling you” she’s tired, respect this and put her down to nap or sleep.
  • If she’s four months old, be careful to avoid developing bad sleep associations, like using a pacifier or nursing to sleep. With a boy, you can keep the pacifier and/or the nursing for a month or so, since he won’t be ready to soothe himself as early in life as a baby girl can!


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Rob Lindeman

Rob Lindeman is a sleep coach, entrepreneur, and writer living in Massachusetts. Ready to Get Rid of the Pacifier? Sign up for our FREE Video eCourse: The Paci-Free Method

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