What's Really Happening During The 4 Month Sleep Regression?

What's Really Happening During The 4 Month Sleep Regression?

At around four months of age, the way in which babies sleep changes.

From the outside, this can look - and feel - very much like a regression.  After all, babies often start to wake more frequently during the night, and settle less easily at nap-times.  This wakefulness and disruption can often leave parents feeling anxious, as well as exhausted, especially with the near-constant (and unfounded) social pressure for babies to sleep through the night.


So what's really happening when a baby reaches this infamous age and stage?

Far from a sleep regression, the four month leap marks the start of a fundamental developmental progression for our babies.

This is the age where the way in which babies sleep, also referred to as their sleep architecture, shifts.

Gone are the newborn days, in which babies sleep in two stages - active and quiet sleep.  For some little ones, though certainly not all, sleeping in these two stages as tiny infants can result in relatively long stretches of sleep.  So when sleep cycles start to mature at around four months, it's easy for us to worry that something is amiss (it's not).

During this progression, sleep cycles begin their monumental shift towards a more adult-like sleep pattern.  Though the end result of this shift won't be complete for years, the early phase is often very clear.  This is because babies begin to experience four stages of sleep from around three or four months of age: three stages of quiet sleep (instead of one, as newborns), as well as active sleep.

On top of this progression and alteration in the structure of how a baby is sleeping, there are also other compounding factors that can affect sleep at this age.

Neurologically, the brain is maturing.  Physically, coordination and strength is rapidly developing (hello, rolling!). And socially, connecting with others is becoming more of a priority, with spontaneous smiles aplenty and facial expressions readily mimicked.

With so much development taking place, babies need the security, comfort and refuelling that wake-ups and night feeds provide.  Add to this the fact that a child's overall daily sleep needs reduce at this point, too...and those wake-ups start to make a little more sense.


If disrupted sleep is the norm during this phase, how on earth do we cope as parents?

- Try not to panic. This is a phase, and the impact won't necessarily be intense.

- If things do get intense and exhausting, cut yourself some slack.  Lower expectations, reduce non-essential commitments, ask for practical support, and order take-out.  Cut those cuttable corners wherever you can.

- Support baby's rhythms with plenty of outside time and no-stress daily rhythms.  Grab a copy of my Nap So Simple eBook if you haven't already, to help with this.

- Support skill-development by facilitating lots of time to practice new skills (such as rolling) during the day.

- Flow and flex according to baby's needs, without worrying about "bad habits" (they don't exist!)  This may mean a temporary change to routine, or supporting different routes into sleep (such as motion or contact naps).

Overall, this is a phase that gets a really bad rap.  But if we look at this stage as a progression, as opposed to a regression, we can start to trust the process a little more.




Tham, E. et al.,"Infant sleep and its relation with cognition and growth: a narrative review", 2017

Wielek, T. et al., "On the development of sleep states in the first weeks of life", 2019

Sadeh, A. et al., "Sleep and sleep ecology in the first 3 years", 2009 

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