6 minute readWhat are the different stages of baby sleep?
Newborns experience very short sleep cycles — they typically last around 30-60 minutes at a time, averaging around 50 minutes — with each of these cycles split roughly 50/50 between two distinct sleep stages: active sleep and quiet sleep, which are sometimes referred to as REM and NREM sleep respectively.
While we apply these terms in the context of baby sleep, however, newborns don’t experience REM and NREM sleep in the exact same way adults do — primarily because they don’t yet carry the significance they do for adults in terms of restorative functions.
As your baby gets older, their sleep architecture will continue to evolve into a more “adult-like” pattern, where they’ll spend a decreasing amount of time in active (REM) sleep and more in quiet (NREM) sleep. The NREM sleep stages will also become more varied and complex in nature, increasing each cycle’s restorative powers.
It’s important to note that when we refer to sleep cycles, we’re not necessarily talking about the total duration of each sleep but the repeating pattern of different stages that occur each time we sleep — newborns may sleep for up to 4 hours at a time, while sleep cycles typically last no more than an hour, so they’ll usually experience multiple sleep cycles during each snooze, quickly cycling between each stage.
Here’s a breakdown of each newborn sleep cycle stage in more detail:
Stage 1: Active sleep
Active sleep is a baby’s version of REM sleep, and refers to a lighter sleep stage where their brains remain active and more responsive to external stimuli. REM stands for rapid eye movement, so called because the eyes tend to move around under the eyelids during sleep.
While active sleep in babies shares similarities with adult REM sleep, babies in active sleep often appear quite restless and agitated — while it’s usually not because they’re grouchy or uncomfortable, newborns tend to wriggle, twitch, squirm, breathe erratically, and make noises during active sleep.
How long does it take a baby to enter REM sleep?
Newborn sleep cycles are a little like adult sleep cycles in reverse. So while REM sleep occurs roughly 90 minutes into the sleep cycle for adults and is the last stage they experience before the cycle “resets”, active sleep is the first sleep stage a baby enters. It will usually begin within just a few minutes of them first drifting off.
How long does REM sleep last in newborns?
Sleep cycles typically last somewhere between 30 and 60 minutes for a newborn, with each cycle made up of roughly 50% “active” sleep. Therefore if your baby normally experiences an hour-long sleep cycle, you should expect them to spend roughly half of this time in active sleep before transitioning into a deeper slumber — though of course, this can vary per baby and some may have slightly longer or shorter active sleep cycles.
Depending on how long they sleep for, a newborn might go through multiple sleep cycles in a single period of sleep, so they’ll usually experience the transition from REM to NREM sleep (and back again) more than once.
Stage 2: Quiet sleep
Non-REM or “quiet sleep” is the second major sleep stage a newborn enters. It occurs after active (REM) sleep, and is a much deeper, more peaceful sleep state. The restlessness that characterizes active sleep will subside, breathing will become more consistent, and your baby will typically be much harder to wake.
A baby’s brain is much less active when they reach the quiet sleep stage, and save for the occasional twitch or whimper they’ll generally lie still and silent, sleeping soundly — at least until they wake or the sleep cycle begins again.
When do babies enter quiet sleep?
In a typical newborn sleep cycle, the transition from active (REM) to quiet (NREM) sleep occurs about halfway through. It depends on how long your baby’s sleep cycles usually last, of course, but let’s say they’re normally around 60 minutes — the first half will be spent in active sleep, and they’ll enter the quiet (NREM) sleep stage around the 30-minute mark.
How long does quiet sleep last in newborns?
While REM sleep typically makes up around half of every sleep cycle in a newborn, the other 50% is spent in quiet or non-REM sleep. So, as with active sleep, quiet sleep will usually last roughly half of an hour-long sleep cycle. If your baby has shorter cycles, they’ll naturally spend less time in NREM sleep.
When do baby sleep patterns change?
The 50/50 pattern of active versus quiet sleep is typical of a newborn’s sleep cycle, and will usually be the way they experience sleep for roughly the first 3 months. As they get older, they’ll begin to transition to a more complex sleep pattern — their sleep cycles will lengthen and include a number of different stages.
Around 4-6 months, the shift to longer periods of non-REM sleep will become more noticeable. Your baby’s sleep cycles might last 60-90 minutes, and be made up of more stages of quiet sleep. This means they’ll spend less time in “active” or REM sleep (around 30-40% of each cycle) and more in a more restful, restorative sleep state.
As they reach their first birthday, your baby’s sleep cycle will typically resemble that of an adult, with this evolution in sleep structure helping to support their brain development and growth. Adults go through four different stages of sleep, including three non-REM (NREM) stages and one REM stage — which is typically where dreams occur.
Here’s a rough breakdown of baby sleep stages as they get older:
NREM 1: Drowsiness. Your baby is transitioning between wakefulness and sleep. They may have slow eye movements and their muscles start to relax.
NREM 2: Light sleep. Their breathing becomes more regular and their heart rate slows. Eye movements stop and their body temperature drops.
NREM 3: Deep sleep. The deepest stage of non-REM sleep, often referred to as “slow-wave sleep”. Their breathing and heart rate are at their slowest and it’s difficult to wake them.
REM: Active sleep. The brain becomes “active”, almost resembling a waking state. They may become restless and fidgety.
While your baby’s sleep cycles will be even more adult-like by 12 months — up to 80% of each cycle may be made up of non-REM sleep — but it’s not until they reach around 5 years old that their “sleep architecture” is fully developed and closely matches that of a grown-up.
As your newborn navigates through their early sleep stages, it can feel like a never-ending cycle of eat-sleep-cry-repeat. But with each new phase, your baby’s sleep habits are evolving, moving them one step closer to longer, deeper rest. So, while it might seem your sleepless nights will never end, eventually you’ll both be able to enjoy peaceful, uninterrupted sleep.
Reviewed by Sleep Consultant, Rosey Davidson in November 2024.