What are sleep cycles? If you have spent any time researching baby sleep, you have certainly done some reading about them. Understanding them more deeply will help better inform your parenting and decisions around how to handle nighttime wakefulness or short naps.

For starters, it is good to know that newborns, infants, toddlers, and adults have unique sleep patterns. Understanding them is important to understanding how to get your baby to sleep their best.

Newborns

Newborns only experience two stages of sleep. REM (rapid eye movement) and non-REM (non-rapid eye movement). Their complete sleep cycle is around 45-minutes long, including the time spent in light sleep, deep sleep, and back up to light sleep again.

REM sleep is also called active sleep, and it is light sleep where dreams occur and eyes move rapidly back and forth. You have probably noticed your baby’s eyes flitting back and forth while you marveled at your sweet, sleeping newborn. Pretty strange to observe, but REM sleep is critical for your child’s development. Newborns spend about 50% of their sleeping hours in light sleep. During this time, they synthesize much of the information they take in during their waking hours, process their experiences, and form brand new neural connections. Blood flow to the brain is increased during this time and your baby’s body is busy doing the work of cognitive development.

They cycle very quickly from REM sleep into deep sleep, where they spend the other 50% of their sleeping hours. Deep sleep is where much of your little one’s physical development occurs- muscle repair and protein synthesis. The old adage that babies grow in their sleep holds truth!

Just to toss in another sleep curveball, newborns enter the world with their days and nights thoroughly confused. They are not yet producing their own melatonin to regular their circadian rhythms. They rely on us to teach them the social cues for day and night while we wait for their sleep patterns to solidify.

Infants 3-4 months and up

As babies get a little older, their sleep becomes more complex. By three-months of age, they are producing their own melatonin and should have cleared up and day and night confusion. They also have likely outgrown any PURPLE crying or colic (thank goodness!).

At around this age, their sleep becomes more interesting and challenging. They will start to spend more time in stages of light sleep- meaning a greater chance of them waking and signaling for help going back to sleep.

Your infant will still spend around 50% of their sleep in active REM sleep, dreaming and synthesizing all they have learned. However, instead of spending the other 50% in deep sleep, they spend about 25% in truly deep sleep, and 25% in lighter stages of non-REM sleep.

This light sleep is what makes your life as a new parent more challenging. Your sweet bundle becomes more difficult to transfer to the crib. They seem to wake more frequently than before. They are more easily disturbed by environmental sounds, temperature changes, or their own startle reflex. Just when you thought you had this whole baby sleep thing down, your baby throws a wrench into the picture.

Your baby’s total sleep cycle will still be about 45-minutes long. The first 20-minutes are spent in REM sleep, then they will dip into deep sleep, and cycle up to light sleep, and then either wake or repeat.

Adult Sleep

Just for comparison, let’s take a look at adult sleep. We experience sleep differently than our babies do.

You experience four complete stages of sleep over a cycle of about 90-minutes.

1. The first is drowsiness. You may not even realize you are falling asleep.

2. The second is light sleep. This is the first point at which you would recognize you were asleep if you were to be woken.

3. The third is deep, restorative sleep. Your body begins the work of repairing muscle tissue, restoring energy, growing, and keeping your immune system strong.

4. The last stage is REM sleep, light but active sleep full of dreams.

It is often at this point that we might wake. If you wake between sleep cycles, you likely remember some details of the dream you just woke from. You may roll over, check the clock, and go back to sleep. As the night goes on, we spend more time in REM sleep and less time in deep stages, which is why you are more likely to remember your dreams from the early morning hours than you are dreams from before midnight.

Back to Baby Sleep: The Four-Month Sleep Regression

Not every family was blessed with a unicorn sleeper, who sleeps most of the night and takes wonderful naps right from the get-go. So many families step into parenthood thinking that they hit the jackpot with great newborn sleepers. Just when they get comfortable, they hit the dreaded four-month sleep regression (which can set in anytime between about three and five months) and find that their dream baby was replaced by one who wakes a million times each night.

It can be so frustrating, particularly in the middle of the night when all we want to for everyone to get back to sleep. I find that waking during the night is somewhat less annoying if I understand why it is happening. If you understand sleep cycles, you might also begin to understand why you may have rocked your baby until they were soundly asleep, placed them in their crib, only for them to wake a few minutes later.

Babies go through many, many sleep cycles each night- every 40-60 minutes! If they happen to rouse between those cycles during a stage of light sleep, they probably struggle to put themselves back to sleep, especially if they are dependent on nursing, a bottle, rocking, or some other prop to fall asleep. This is when they cry and call for you to come help them return to sleep. This may be multiple times each night and you and baby are both missing out on much-needed rest. This is also why, after you rocked your baby for 20-minutes, lay them down sleeping peacefully, they awaken after another 20-minutes- right around 40 total minutes of sleep, or a single total sleep cycle.

Why Sleep Training?

Sleep training teaches your child to fall asleep independently, so that not only can they go to sleep for nighttime and naps, but they can return to sleep if they wake between sleep cycles and know that all of their needs are met. If they are not cold, hot, hungry, or in pain, they will probably go back to sleep without your help. It doesn’t mean crying-it-out and it doesn’t necessarily mean weaning, though you will likely find your sleep trained child will wake to eat less frequently. [The decision to fully eliminate feeding rests with you and your pediatrician.]

The earlier you start- ideally right around that four-month regression- the easier it is to be incredibly gentle on your baby. I’m talking no tears, totally painless and easy. I would never, ever suggest a parent let their tiny babe cry-it-out (or a big kid for that matter!). Sleep training just means we want your baby to learn to get to sleep without the feeding and rocking they have grown so used to.

This becomes even more important as sleep grows lighter in the early morning hours- your child is spending almost no time in deep sleep, meaning many opportunities to wake from light sleep in the wee hours.

How to get started sleep training

1) if you haven’t yet started to lose sleep or hit a major regression, now is the time to be proactive! Practice putting your baby down awake as often as possible. Don’t leave them to cry, but some fussing and squiggling around is normal. It may not always work, but practicing is a great start!

2) If you are in the thick of a regression, or maybe the regression just never seemed to end for your family, you need to consider what works best for you and your little one. Are you content with the sleeping arrangement in your house? If so, great! Don’t change a thing. If you’re tired to being up a lot, let’s talk about how to reduce your child’s wakefulness and start getting better sleep.

I can provide you with a selection of methods that best suit your family and your child, and walk you through the process step-by-step to make the road to better sleep as smooth as it can be. Check out package options here and hop over to Instagram for more daily content.