The early months of a baby’s life are a time of incredible growth, not just physically and cognitively, but in sleep too. During this period, babies are learning the difference between day and night as their internal body clock starts to develop. At the same time, their ability to produce melatonin, the hormone that regulates sleep, is maturing.
On top of that, the very structure of their sleep is evolving. Newborn sleep starts as a simple pattern,but over time, it transforms into the more complex, multi-stage sleep cycle that older children and adults experience. Understanding these changes can help parents navigate what is often a challenging but completely normal phase.
How to understand newborn sleep
Newborns have only two main stages of sleep:
- REM sleep (Stage 4) – About 50% of a newborn’s sleep is spent in REM, which is essential for brain development.
- Deep sleep (Stage 3) – The other half of their sleep is deep, restorative sleep that supports growth and cell repair.
Around four months of age, babies undergo a significant change in their sleep pattern. Many parents call this a “sleep regression,” but I like to think of it as a period of progression. During this time, babies may start waking more frequently, taking shorter naps, and finding it harder to settle. This is because their sleep cycle is maturing and becoming more like an adult’s but still much shorter, usually lasting just 30–60 minutes.
Why is my baby waking up more often suddenly?
As babies transition into a mature sleep cycle, their REM sleep decreases to around 25% to make room for Stages 1 and 2 (light sleep). Because light sleep is easier to wake from, your little one may start to wake up more frequently during the night.
While brief awakenings are completely normal for everyone, adults usually roll over or resettle without much thought. Babies, on the other hand, don’t yet have these skills. They often rely on specific conditions to fall asleep, such as feeding, rocking, or gentle pats. When they wake between sleep cycles, the absence of these conditions can feel disorienting, which is why they might cry or struggle to go back to sleep.
Although it can feel overwhelming, this phase is temporary. With patience and consistency, your baby will gradually adjust to the new sleep cycle, eventually settling into a more predictable sleep pattern.
Baby sleep cycles explained
Knowing what happens in each stage of sleep can help you understand your baby’s nighttime behaviours:
- Stage 1 & 2 – Light Sleep:
This is when your baby is starting to calm down but is still easily awakened. You might notice sudden muscle twitches, called hypnic jerks, especially if there’s noise. Using pink or white noise can help reduce disturbances and support longer stretches of sleep. - Stage 3 – Deep/Slow Wave Sleep:
In deep sleep, your baby is fully settled. Their body grows, repairs cells, and slows their breathing. Babies in this stage are much harder to wake. - Stage 4 – REM Sleep:
REM sleep is when the brain is very active. Your baby’s brain is organizing thoughts, consolidating memories, pruning unnecessary connections, and growing new ones. This stage is crucial for cognitive development and helps them process everything they’ve experienced during the day.
The first months of a baby’s life are full of change and sleep is no exception. While frequent night wakings and shorter naps can be exhausting, they are a normal part of your baby’s development. By understanding the stages of sleep and what your baby needs to settle, you can navigate these early months with a bit more patience and confidence.
Remember: this period is temporary, and it marks the start of a more structured, bedtime routine and predictable sleep pattern that will serve your child for years to come.
If you feeling overwhelmed by your babies sleep, I’m here to help! Book in for a free 15-minute call to chat it through.
