Understanding Your Baby’s Sleep Cycle

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Last Updated: Tue, February 25, 2020

Medically reviewed by:

Carlos Del Rio-Bermudez


Carlos is a neuroscientist and a medical & science writer  with more than eight years of research experience in  the  field of Neuroscience. Prior to working full time as a  medical writer, he was a postdoctoral researcher at the  University Hospital of Bern (Switzerland). Carlos  obtained  his PhD from the University of Iowa (USA),  supported by the Fulbright Program.

Some of the areas Carlos focuses on are RNA  therapeutics, Rare Diseases, and REMS/RMPs. He has  authored multiple original research papers in top  journals in the field, book chapters, and periodicals.  Carlos has also participated in international scientific  meetings; most notably, he was invited to present his  dissertation research at the 2018 Gordon Research  Conference on Sleep Regulation and Function.

Your baby spends more than half of the first year sleeping. And studies show that this sleep in the first year is crucial for the maturation of the central nervous system (CNS) and future cognitive, psychomotor, and temperament development.

Because sleep is so important for your newborn, it is a good idea to learn what the normal baby cycle looks like so that you can notice if something is off. Early recognition and treatment of sleep problems can do a lot for the future physical and mental health of your child.

So, what does the normal baby sleep cycle look like? How does it change with age?

Watch our video to learn more about the science behind infants’ sleep

What Happens During Sleep Anyway?

It turns out that not all sleep is the same. Indeed, scientists have known for some time know that our sleep is organized in cycles, and each cycle consists of different stages.

In most healthy adults, sleep begins with the so-called non-REM (NREM) sleep, in turn, comprised of several substages. As NREM progresses, our sleep becomes “deeper,” and we become less responsive to external stimulation, being harder and harder for us to wake up. Following NREM sleep is REM sleep, named after the typical “Rapid Eye Movements” that are observed during this stage. In healthy adults, REM takes up to 25% of total sleep, and it is where most of our dreaming activity occurs.

Each part of the sleep cycle is important and plays a unique role in our overall wellbeing. However, it seems that stages complement each other and that sleep continuity is essential for feeling refreshed in the morning.

A complete sleep cycle usually lasts for 90-120 minutes, during which we shift through the different stages we just described. However, the relative time we spend in each stage changes with age and is affected by myriad circumstances; to make things a bit more complicated, the time allocated to each stage is different across sleep cycles as the night goes on…

So, is it the same with babies?

Well, yes. And no.

Babies do experience different sleep stages, but the relative amount of time they spend in REM sleep is a lot higher than what is observed in adults. This fact inspired the hypothesis that REM sleep plays a crucial role in early development.

What Does the Baby’s Sleep Cycle Look Like?

You may have noticed that babies sleep a lot more than adults. In fact, newborns sleep for 16-17 hours a day. That’s twice as much as what most adults are getting.

Another interesting fact about baby sleep is that it is evenly spread across the 24-h day, and they don’t have that extended uninterrupted nightly rest. This is what sleep experts call “fragmented sleep,” and at these ages is a consequence of a still-developing circadian system.

The circadian system dictates (among others) the timing of basic physiological functions, including sleep, temperature regulation, and feeding. Unfortunately for babies, their internal clocks are not fully coupled to relevant environmental cues, most notably external light, so it takes a while for them to adjust to the 24-h sleep-wake rhythm.

The brain structures that regulate the circadian modulation of sleep, including the suprachiasmatic nucleus (or SCN), continue to develop within the first 2-3 months of life. Until the circadian system is fully developed, babies sleep in even patches of 2-3 hours. One of the reasons why they don’t sleep for longer periods is that their frequent feeding needs interfere with the sleep cycle. 

At around 3 months, babies can eat larger amounts of food, which makes them able to sleep at stretches of 5 hours at a time.

Less demanding feeding schedules, along with the progressive maturation of their biological rhythms, allow the average 6-month-old to sleep through most of the night.


And what about sleep architecture?

Studies show that babies experience different sleep stages, including NREM and REM. However, newborns spend about 50% of their total time asleep in REM sleep; healthy adults spend only 20% to 25% of their sleeping time in this stage.

Regarding duration, it is also important to note that baby sleep cycles are shorter than in adults, lasting approximately 50 minutes during the first months of life.


How Long Do Babies Sleep on Average?

After reviewing the scientific literature, the National Sleep Foundation made age-appropriate sleep guidelines. It goes like this:

But that doesn’t mean you should start your stopwatch anytime your baby goes to sleep and stress about it. If they seem to be functioning well, there is no need to worry if their sleep schedule lightly differs from these guidelines. Look for sudden behavioral and mood changes; these could actually indicate that something is off.


What Sleep Stage Is Your Baby in?

Determining your baby’s current sleep stage is extremely important to avoid waking the little one off at the wrong time. For instance, disrupting deep sleep will lead to a fussy, moody baby.

There are some behavioral features that can help you guess what sleep stage your baby is in:

Are you familiar with the feeling of tiredness after a nap that was supposed to help you recharge the batteries? Well, that happens when you wake up from deep sleep, so you may want to avoid waking your baby up in this stage to prevent the usual tantrum.


Can You Do Anything to Make Your Baby Sleep Better?

It can sound a little weird, but sleep is actually a skill you learn, and it doesn’t come naturally for everybody. And while some babies may be natural-born good sleepers, others could have some problems learning how to rest efficiently.

Luckily for you, you can help your little one by using some proven tips:


Be sure to check our video on the best sleep tips for new parents, where we discuss in-depth how to improve your and your baby’s sleep. In this video, we discuss sleep training techniques that can teach your baby to sleep on its own.


Closing Down

Babies spend most of their time sleeping, and it is essential for proper brain and body development.

This is why you want to make sure your newborn gets the best sleep possible. Observe them, watch out for any potential problems, and consult with your pediatrician or sleep specialist if something seems odd.

And if there is anything more you want to know about your baby’s sleep, feel free to post questions in the comment section. We will be happy to answer.


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Dusan is a biologist, a science enthusiast and a huge nature lover. He loves to keep up to date with all the new research and write accurate science-based articles. When he’s not writing or reading, you can find him in the kitchen, trying out new delicious recipes; out in the wild, enjoying the nature or sleeping in his bed.