There is a lot of talk about how a baby’s sleep dramatically changes around the 4-month mark. You might have had an awesome sleeping newborn and suddenly they’ve started waking a lot more in the night and catnapping in the day.
This is commonly called the 4-month sleep regression; however, it is better not to think of it as a regression but more of a maturation of your baby’s neurological development. Their brains are developing and their sleep is becoming more like ours as adults.
An adult sleep cycle goes through periods of deep sleep and periods of REM sleep. REM sleep is a lighter sleep where we dream and are more likely to be woken if something is different or bothering us in our environment. Our deep sleep is where we are unlikely to be woken. Adult sleep cycles are about 100 minutes long, then we rouse slightly and fall back asleep again, into the next sleep cycle without even realizing it.
Young babies are a bit different. They have periods of active sleep and periods of quiet sleep. Active sleep is what the baby enters straight after falling asleep, this is like REM sleep in adults and they can be easily woken during this time. They breathe shallower, can grunt, cry out and if anything is bothering them they are easily woken. During this phase your baby is likely to wake if they went to sleep in your arms and you put them down. After active sleep they enter quiet sleep - this is when breathing is more rhythmic and it is like the deep sleep stage in adults. A baby’s sleep cycle is about 45 minutes in total and if tired enough, if nothing is bothering them and have a full tummy, babies under 3 months will rouse between sleep cycles but then enter into another 45-minute cycle of active through quiet sleep until they have had enough restorative sleep and wake up.
After 3 months babies go through a massive development in their sleep cycles and they don't drift from one to another so easily. By four months they actually wake completely at the end of a sleep cycle and need to consciously try to go back to sleep. This wakefulness is the part that is referred to as the “four-month regression”.
In babies 0-12 weeks, the way your baby goes to sleep at the start of their nap will have little impact on their ability to stay asleep longer than one sleep cycle; you're not going to "spoil" your baby or ruin their sleep if you are rocking or settling your baby to sleep in those first few months, despite what some old wives tales say! However, sleep habits are very easily formed in babies older than 3 months. The way we put these babies to sleep will dictate how they learn to go to sleep in this new phase of their development. We refer to this as creating “sleep associations”; cues or behaviours your baby associates so strongly with going to sleep that they can’t sleep without them. The most common sleep associations for babies are feeding, rocking or patting to sleep or the use of a pacifier (which can be a real pain in the butt until they learn to replace it themselves at around 8 months of age!).
The 4 month regression affects babies in this way:
- sleep is becoming a conscious activity for babies at this age - I like to think of it as "they won't just fallasleep anymore, they actively need to go to sleep"
- therefore they need to re-learn how to do it now that their brains are treating sleep a bit differently from when they were younger
- the way babies are put to sleep or go to sleep at the start of a nap or at bedtime is the only way they learn how to go to sleep
- if they then wake at the end of a sleep cycle, 45 minutes later, they will need to go back to sleep the same way they fell asleep
- if that same way of going to sleep isn't there or can't be replicated by them alone, they will not be able to go back to sleep without it
- this is why, if you fed, used a pacifier, rocked or patted your baby to sleep at the start of the nap or at bedtime, your baby might now be waking every 45 minutes in the day and 1.5- 2 hours in the night and needing your help to go back to sleep
- if your baby is relying on any parent-controlled sleep associations, they are not going to be able to self-settle, resettle during naps in the day or sleep through the night from around 4 months onwards.
And this "sleep regression" won't go away... Unlike the 8 or 12 month sleep regressions, which are all linked to measurable periods of development, the 4 month regression/progression is the only one your baby won't simply "grow out of" unless they are no longer relying on you to actively put them to sleep.
So, the best way to tackle this stage in your baby's development is to foster good sleep habits from early on, rather than have to try and change any parent-controlled sleep associations like rocking or patting down the track. Giving your baby the chance to learn to self-settle is a crucial element in getting through this stage of disrupted sleep. The Little Ones Sleeping and Feeding Patterns are the best place to start because your baby will be good and ready for sleep when you're trying to put them down, making it a lot easier for them to go to sleep on their own.
A few more good sleep habits you can be fostering are:
- sleeping your baby in a totally dark room to allow the release of the sleep hormone melatonin. Black out blinds are an easy and inexpensive way to darken a room. Use them in the nursery or kids bedroom or take with you when traveling to use in a hotel room or other temporary accommodation.
- use white noise for the duration of your baby's naps and overnight as a positive sleep association
- use of a swaddle in babies under 5 months can help them resettle between sleep cycles
- teach your baby to replace their own pacifier if over 7 months.
- allow your baby to sleep in their own bed for their daytime naps as they will learn to associate their bed with sleep and this will help them settle and resettle easier during the night in their own bed
- always give your baby the chance to resettle themselves if they wake between sleep cycles - rushing in and assisting them straight away is not giving them the chance to practice this new skill!