Whether or not you plan to (or currently) “sleep train” your baby, new parents and parents-to-be are familiar with wondering if their baby will be a “good sleeper,” or if they will be up all night long. It seems as though the instant you bring your baby home, strangers and family members start to ask “ohhh is she sleeping through the night yet?”

For some, it’s nothing more than an innocent question, but for others it can be obnoxious. Tired parents will sense a notion of judgment or eagerness to hear of the parent’s failure to being able to keep their baby asleep, or they just dread hearing the question because it reminds them of how little sleep they are actually getting.

Good sleeper or not, there’s one thing that I think we can all agree on – that newborns sleep differently than young infants, and young infants sleep differently than older babies. When Jia was sleeping in our living room in her crib, Jeff and I tiptoed around our 1-bedroom condo like you wouldn’t believe. For a handful of weeks I was living on-edge after 8:30 PM. I dreaded bedtime. Whether it was the dogs barking at something they heard outside our window, needing to take a quick trip to the fridge, opening and closing our squeaking front door (thank you WD-40) or wondering if the dropping of the shampoo bottle in the shower was enough to rouse her from her light sleep, I was going nuts.

Nowadays, in her own room sleeping 11-11.5 hours straight, I still wonder: how come our friends’ toddler needs the clanking of pots and pans or loudly opening and closing dresser drawers to wake up, whereas sometimes it seems Jia can sleep through an army passing by her door but other nights her sleep will be disturbed by Jeff blowing his nose next door?

We started talking about this and I became curious – how are sleep patterns and brain waves different for infants and toddlers, and when do they change?

Sleep Cycles

The average sleep cycle for an adult goes through REM (rapid eye movement; “light sleep” with dreaming, restorative sleep that helps reinforce memories, easily awoken) then onto NREM sleep (non-REM, “deep sleep”, has four stages, and less likely to awaken) in 90-100 minutes. The EEG (electroencephalogram, which is a monitor that uses electrodes attached to the scalp to show brain wave activity) during light (REM) sleep shows similarly active patterns of brain activity to those seen when someone is awake. Brain waves during NREM sleep are “slow wave sleep,” which is why the person is in a deeper sleep. Brain waves are suppressed and breathing and heart rates slow, and blood pressure is lowered during deep NREM sleep. This means the person is in a very relaxed very deep sleep. 

All About Babies

Babies are light sleepers. For the first nine months, babies’ sleep cycles last about 50 minutes (source). This explains why normal nap times usually last around this length of time. But this also helps to explain why babies are aroused during sleep much more frequently. Additionally, babies spend 50% of their sleep times in light sleep and 50% in deep sleep, versus adults spending 20% of their sleep in REM and 80% in NREM sleep. Remember, as much as it stinks that babies are such light sleepers, it’s the light/active sleep time that is beneficial for brain development. And here’s another silver lining – the NIH’s National Library of Medicine (MedLine Plus) says that the ability to wake up decreases risk of Sudden Infant Death Syndrome.

Here’s a cool diagram (source) showing how the proportion of sleep spent in “light sleep” decreases with age as babies get older (thankfully!!):



This also is a likely contributor to improved success in getting your baby to sleep through the night once they are past the 5 month mark, where % of REM sleep drops from 40% to 30%.

EEG waves (source) when Awake, in REM and NREM sleep:


Baby Sleep Cycles:

Babies’ sleep is categorized into two types: active and quiet sleep. Active sleep, where baby is likely to be aroused from sleep, comprises of body movements, fast and irregular breathing rhythm, grunts and other baby talking vocalizations, and eye fluttering, like REM sleep waves in adults. Parenting says that the first 25 minutes or so after falling asleep is when they are most likely to be awakened. Quiet sleep for babies, similar to deeper NREM sleep waves in adults, is characterized by less body movement, no eyelid fluttering, and rhythmic breathing.

By Age (from the National Sleep Foundation)

Newborn to 2 months:

  • Awake when needing feeding, changing, nurturing
  • They sleep 10.5-18 hours in a 24 hour period, with waking periods of 1-3 hours at a time
  • Most is active sleep, processing their new world
  • Sleep characterized by twitching, smiling, sucking, appearing restless
  • Swaddling is encouraged at this age to suppress twitches to help baby sleep longer periods

3 months – 11 months:

  • Night feedings not usually necessary at approx 6 mos of age
  • 70-80% of infants “Sleep through the night” by 9 months
  • Expect 9-12 hours of nighttime sleep, more time spent in deep sleep as they get older (yay)
  • Twitching and body movements decrease after 6 months, so less likely to wake themselves during sleep due to movements. Swaddling not as necessary.
  • 1-4 Naps per day, between 30 minutes to 2 hours each (more naps the younger the infant)
  • National Sleep Foundation encourages putting babies down when drowsy (not asleep) to encourage “self soothing” throughout waking periods at night.
  • At this age, babies will learn to be accustomed to parents soothing them when they cry and may continue to do so if not learning to self soothe.
  • Encourage a calm and regular bedtime routine
  • Establish a regular “sleep environment”

Toddlers 1-3 Years:

  • Need 12-14 hours of sleep in a 24 hour period
  • Usually only need 1 nap per day once approaching 18 months of age
  • Nightmares are common
  • Daytime sleepiness may indicate poor sleep patterns
  • Difficulty sleeping due to motor skills development occurs at this age
  • Maintain consistency in bedtime routine and time
  • Set limits for bedtime
  • Encourage security blanket or other object to help sleeping

Matured Sleep Cycle in Infants

So the main question I’d ask if I were reading this post: When can I expect my baby to really start sleeping deeper? Well, according to Dr. Kothare of Boston Children’s Hospital, NREM sleep stages start to mature at around 4-6 months.

So with that in mind, let’s all cross our fingers that if our babies aren’t “good sleepers” right now, pretty soon they will be.



University of Washington: Neuroscience for Kids -Sleep:

National Institutes of Health – National Library of Medicine SIDS:

Baby Sleep Patterns: A Guide for the Science-Minded

National Sleep Foundation Children and Sleep –

Harvard University Changes in Sleep With Age –

Artifacts Variants and Epileptiform Activity Observed on PSG in Children