4 to 6 Month Maturing Sleep

The Four Month Sleep Regression

Every new parent is at least somewhat prepared to be up through the night with a newborn. “Get sleep now, it’s your last chance” is a common warning to parents expecting their first baby. And many quickly become adjusted to this period of sleep deprivation because, in the very least, they are confident that they are meeting their baby’s needs – hunger, diaper change, hunger, diaper change, repeat. You quickly become equipped with a quiver of techniques to lull baby back to sleep...at least for a little while until she makes her next request.

“But my baby was sleeping so well!”

You may notice that suddenly around 3 or 4 months the tried and tested skills you have mastered to lull your little one off to sleep with relative ease seem to stop working, or only work some of the time. Your baby is now waking up MUCH more frequently than before and you can’t for the life of you figure out what she needs anymore. “You can’t possibly be hungry again… it’s only been 45 minutes!”

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A Critical Period of Development

It turns out that between 4 and 6 months of age, babies’ sleep patterns are undergoing such vast maturation that the dream world, and as a result the waking world too, is entirely different than it was before. This is a good thing given the incredible benefits of sleep, but we have to wade through some pretty murky waters to get there.

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Some nights I saw every hour of the clock. And naps were all but non-existent. Needless to say, I felt like an intoxicated zombie and quite honestly hit a pretty dark spot in my post-partum life.

But I soon perked my ears up and realized that every new mom that I was acquainted with (and there’s no short supply in my town) was experiencing the exact same sleeping patterns that I was.

After settling in with a baby that would sleep 4, 5, sometimes even 6 hour stretches, they were now dealing with night wakings every 45 to 90 minutes and a near complete loss of naps.

Surely something so disruptive would have gone the way of the dodo by now. What is nature intending in such a universally challenging shift?

Well from an evolutionary standpoint, usually something that seems so maladaptive actually has benefits that outweigh the costs.

Going through changes.

The biggest change that happens at this time is that the previously undifferentiated quiet sleep that kept your baby so happily and deeply snoozing now takes on the four distinct stages of NREM sleep.

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Whereas your newborn used to enter sleep through a REM cycle, she will now fall asleep through the gradually deepening phases of NREM sleep – this means that arousal is much more likely if anything changes during the “falling asleep” phase. While you may have been able to bounce your newborn to sleep and immediately transfer her to an alternative sleep surface (be it a co-sleeper, bassinet, or crib), now she will notice the shift if not provided with time to enter into deep sleep.

This accounts for a lot of participation on your part if baby relies on your presence to get to this point. And this is why soooo many sources out there will tell you that your baby should learn to fall asleep on her own…. the basis of the whole “put them down drowsy but awake” advice.

Whereas your newborn used to enter sleep through a REM cycle, she will now fall asleep through the gradually deepening phases of NREM sleep – this means that arousal is much more likely if anything changes during the “falling asleep” phase. While you may have been able to bounce your newborn to sleep and immediately transfer her to an alternative sleep surface (be it a co-sleeper, bassinet, or crib), now she will notice the shift if not provided with time to enter into deep sleep.

This accounts for a lot of participation on your part if baby relies on your presence to get to this point. And this is why soooo many sources out there will tell you that your baby should learn to fall asleep on her own…. the basis of the whole “put them down drowsy but awake” advice.

Babies no longer drift from one sleep cycle to the next unphased. During the day, they will fully awaken following their first completed sleep cycle – usually about 45 mins – and if they rely on something, or someone, to help them transition to the next cycle…well it just won’t happen. 

Having filled a portion of their sleep debt, they will wake ready to take on the next part of the day – whether they are fully rested or not. Same thing at night only sleep cycles are slightly longer – about 60-90 mins once fully developed – and the drive to sleep is a bit stronger. This is why it is helpful to establish strong sleep habits at night first before attempting to tackle naptime.

Finally, many babies master the art of rolling by 4 or 5 months, meaning that nice snug swaddle technique that you have been relying on is no longer safe. At the same time, however, the startle, or Moro reflex may still very much be active making it difficult for your baby to make it passed Stage 2 sleep without jolting himself back awake. Fear not, babies typically grow out of the Moro reflex between 4 and 6 months of age, so this often very frustrating transition should not be long lived.

Finally, many babies master the art of rolling by 4 or 5 months, meaning that nice snug swaddle technique that you have been relying on is no longer safe. At the same time, however, the startle, or Moro reflex may still very much be active making it difficult for your baby to make it passed Stage 2 sleep without jolting himself back awake. Fear not, babies typically grow out of the Moro reflex between 4 and 6 months of age, so this often very frustrating transition should not be long lived.

Gone are the days of the on-the-go napper.

This can be a major shift for new parents or for parents trying to meet the needs of older siblings, as you may be much more tied to home if you want to prevent having an overtired baby. And unfortunately, overtired during the day usually equates to more waking at night and more resistance to nap the next day, and so the vicious cycle is born.

Remember that baby that could sleep literally anywhere, making coffee dates, long walks, and car errands a breeze….where did that little person go?

Since your baby now has to shift between sleep stages throughout the sleep cycle, he is also much more aware of his surroundings at various points within the cycle and will undoubtedly wake to even the slightest change in the environment. 

And since some of his sleep debt has been knocked off, he is unlikely to fall back asleep (NOTE: the key here is some debt has been resorbed, not all…. these little catnaps  are the least restorative type of sleep). 

The pivotal moment in future sleep.

An important time to establish strong sleep habits.

Unlike later sleep regressions, the 4-month sleep regression is actually a maturation of the sleep system. It is not something that will simply go away once the developmental stage is complete. Since this shift in neurological sleep machinery makes the act of falling asleep a much more conscious process, this is a pivotal time in establishing strong sleep habits. Shaping behaviour to match development.

Babies are incredibly receptive to sleep cues at this time – they are searching for signals that tell them it is time to sleep or it is time to wake – and the signals we consciously or unconsciously provide can set the stage for the upcoming months or even years of sleep behaviour. Because your previously sleeping baby is now waking regularly, it is very common for parents to quickly jump in and provide the supports that helped baby fall asleep in the first place – rocking, feeding, pacifier. In fact, feeding is the number one sleep association that is established and heavily reinforced during this time; so much so, that baby actually will come to rely on receiving the majority of his calories at night and therefore eat less during the day.

These quickly become ingrained as must-have sleep associations, without which sleep simply cannot occur. Being conscious of what you are providing as early associations can help immensely in creating positive sleep habits. For example, giving a sleep sack blanketed in the smell of you, some white noise, and a dark room can all signal that it is time for sleep and do not require your presence to reinforce upon waking. Establishing a strong and predictable pre-sleep routine that cues your baby to expect that sleep is to follow will provide the confidence and comfort that she needs to prepare to go to bed. And removing yourself from the actual act of falling asleep will mean that when your baby wakes between sleep cycles, she will be able to transition herself happily to the next one based on the body’s internal drive to continue sleeping.

Reinforcing these positive associations at this early stage when all is new and becoming ingrained is extremely helpful if you want to avoid breaking unwanted habits in the future. I stress if because if you are happy feeding or rocking your baby to sleep following each arousal then there is no reason to change that behaviour – they are not inferior sleep associations; they are simply associations that involve you being present. But if you are hopeful that your baby will sleep independently or be able to go to bed for another care provider or take longer naps, for example, then easing them into independent sleep habits in these first post-newborn months will save a lot of strife down the line.

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