Developmental Milestones and Their Effect on Sleep


Sleep Regression | Central Mass MomEveryone has heard about sleep regressions. But what if I told you that sleep regressions are anything but a regression? Regressions are a “return to a former or lesser developed state” (Oxford). That cannot be further from what is actually going on here. They are actually sleep (and developmental) progression, since progression is defined as “the process of developing or moving gradually towards a more advanced state.” (Oxford).

But little JoJo was sleeping just fine and boom, she’s not sleeping anymore – it has to be the 4-month regression! Okay, let me explain.

Developmental Milestones

During the first couple of years of life, your child does a whole lot of growing and develops many new physical, cognitive, social, and language skills. You may have heard of the “Wonder Weeks”, which is a book that catalogs the cognitive milestones your child will go through, when to expect these developments to occur, and how to help your child develop their new skills. The authors even advise that you will likely see changes with sleep patterns while your child goes through the “leaps” in development. Physical milestones include skills such as rolling, sitting, crawling and walking can all cause sleep disturbances as the child tries to master the skills. 

There are many reasons that children experience wakefulness during these developments, but Dr. Dina Cohen of the University of Haifa suggests that “a vast range of changes and psychological reorganization in the babies’ development, increases their level of arousal, influences their ability to regulate themselves and causes a period of temporary instability that expresses itself in waking up more frequently.”

Common Progressions

4 Months

At 4 months, you might see your child start to roll over, start watching and mimicking facial expressions, reaching for items, and beginning to babble. On top of all these, the baby’s sleep is really consolidating into more developed naps and overnight sleep. Instead of the every 60-90 minutes of a newborn, you are seeing a mid-morning nap and, possibly, the early afternoon nap really take shape.

8 Months

At around 8 months, you start to see your child crawling. Crawling is a huge sleep disrupter, and studies show that the earlier they start crawling the greater the sleep disturbance! You are also seeing around this time, they are starting to pull themselves up and even start “cruising” the furniture. Their sponge-like brains are just sucking up all the language skills going on around them. They, again, are getting ready to consolidate sleep – dropping from 3 naps to 2 naps. 

12 Months

Around this time, your child is recognizing sequences and even practicing those sequences. It is very common for there to be sleep disturbances around this time, and many parents think it is time to drop to one nap. Don’t do it just yet! It truly may just be the cognitive advancement they are going through right now! 

18 Months

The first “real regression” in toddlerhood. They have grown leaps and bounds in the developmental department. They are walking, talking, and tantrum-throwing. They now have big feelings and a hard time expressing them. They are pushing their boundaries hard to see where the line is. They have a burst of language that might keep them up talking or singing. There is a lot going on for toddlers at this age. 

How to Handle Sleep Progressions

Stay Consistent

This really is the key to anything sleep-related. This is THE thing I say the most when I am working with clients. Kids need things to stay consistent and predictable. Keep your schedules the same (or similar – sometimes you do need an early bedtime), routines should be the same. They will fall back into a rhythm once they work through their new skill(s). 

Realistic Expectations

Keep in mind that during these progressions, sleep is going to be wonky. Don’t think that it’s going to be that way forever and just follow their “new” schedule. Also, keep in mind that it is going to take a few days or even weeks to work through what they are working through and might take some time to get back into their sleeping groove.

This Too Shall Pass!

And if it feels like it isn’t, take a step back and a deep breath. Look at your routines and schedules. Are they getting enough sleep, enough (or too many) naps? Maybe it’s time for a little tweak to get back to sleep. If it really feels like you’re stuck, ask for help! That is what I’m here for.


  1. Emily, thanks so much for writing this! My son is 10 months and the last few nights he’s been fighting bedtime HARD. He is crawling and cruising furniture, so I guess he wants to keep practicing his new skills > sleep. 😀 “This too shall pass.” That’s my mantra. Thanks for your wisdom! -Ari


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