Human babies change so much in their first months of life – they go from sleepy babies that mainly eat, sleep and poop to happy, alert babies who love to spend time playing and engaging with their parents and can fight sleep just for more snuggles or struggle get to sleep without rocking, feeding or the pacifier. Learning baby sleep science can really help us as parents understand why babies sleep the way they do and why they can struggle. It can help new parents set schedules, anticipate when it’s time for a nap and make sure you promote healthy sleep habits in your baby’s first year.

When babies are born their internal clock isn’t synchronized with the normal 24-hour day.   Because their circadian rhythm isn’t fully developed they aren’t able to differentiate between day and night.  Anyone heard of day and night confusion?  This is why a new baby can be more awake overnight or just sleep the same amount no matter the time of the day.  As they get closer to 6 weeks of age they tend to start sleeping for longer periods overnight, starting with about 4 – 6 hours.ce of baby sleep

Our babies change so much in their first months of life – they go from sleepy babies that mainly eat, sleep and poop to happy, alert babies who love to spend time playing and engaging with their parents and can fight sleep just for more snuggles or struggle get to sleep without rocking, feeding or the pacifier.  Learning the science of baby sleep can really help us as parents understand why babies sleep the way they do and why they can struggle.Sleep changes around 4 months old.

It isn’t until a baby hits 3 – 4 months old that their sleep becomes more adult-like.    They start to produce melatonin around this time.  Melatonin is a naturally produced sleep hormone.  The levels are highest in the evening hours because of darkness, which helps trigger our brain that we need to sleep. 

Instead of falling straight into deep sleep, as newborns do, they first fall into light sleep.  This is why babies often experience one of the most common sleep regressions – the 4-month sleep regression – because they have to learn how to transition between sleep cycles.   Parents often find that their baby who used to fall asleep while being held and transferred to the crib; can’t make that transition any more because they get woken easily when placed into the crib asleep. 

Babies after 4 months of age can also start to push themselves to stay awake and fight much-needed sleep to enjoy the pleasure of their parents’ company.  This is why it becomes very important to be very strict with your sleep schedules and routines – to ward off overtiredness.  Just because your baby doesn’t seem sleepy, doesn’t always mean that they don’t need to go to sleep.  They might just be enjoying you too much to show those sleepy cues.

As you likely know, newborn babies sleep anywhere, anytime and for varying lengths of time.  But often around 4 months, their naps are short as they learn to cope with the change to their sleep cycles.  The morning nap is the one that usually starts to extend first into a nice long restorative nap, and then the midday nap after that. Then around 6 months of age we also see a change to the way a baby naps. By this age they can usually take 2 nice long naps – one in the morning and one at midday. They have learnt to transition through sleep cycles well. If this isn’t happening with your baby it could be a sign that they would benefit from sleep training.

Overnight sleep.

Babies naturally experience many brief arousals throughout their nighttime sleep.  As adults, we do too, but for us, we may just adjust our pillows, move a blanket and fall back to sleep.  For babies, they may make some noise while transitioning back to sleep, or cry out to their parents signaling for help.  They often signal if they are not yet used to helping themselves get to sleep and back to sleep (think sleep association).

Baby sleep vs. adult sleep.

A baby’s sleep cycle differs from that of adults.  An average adult sleep cycle is around 90 minutes, whereas a baby’s sleep cycles are around 50-60 minutes for the first 9 months of their life.  In the simplest terms a baby’s sleep cycle refer to two types of sleep: REM (Rapid Eye Movement) and non-REM sleep (quiet sleep).

In REM sleep babies often move around a lot and make noises. In non-REM babies sleep more deeply. During the REM stage of sleep (the light sleep at the start of the sleep cycle) sleep researches have found that an infant’s brain is developing and consolidating cognitive and physical skills that they have learned throughout their awake periods. sience of baby sleep

Naps.

Naps are incredibly important for babies and having one nap doesn’t compensate for another.  There is more REM sleep in the morning nap, which helps with brain maturation and mental and emotional restoration.  A short-term randomised controlled trials has actually found that babies did better on a memory task when they napped. There is more deep sleep in the afternoon nap, which makes it more restful and physically restorative.  This means that it is important to prioritize both naps for completely different reasons.

Helping your baby sleep.

As much as a little newborn makes sleep look easy, past the newborn phase babies may not be able to go to sleep easily and fall back to sleep at awakenings overnight.  This is why establishing healthy sleep habits from early on, helps them transition to more adult-like sleep at around 4 months.  Although this doesn’t always guarantee you are spared the 4-month regression, sorry!  You can help your baby sleep by ensuring your baby naps and goes down for the night at the right time, teaching him/her to fall asleep on their own, and providing the best environment for safe restorative sleep.

science of baby sleep

 

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