We got the expert advice of Rachel Gorton/Mitchell. She is a certified infant and toddler sleep specialist and the owner of My Sweet Sleeper.
All of us, no matter what age, cycle through different stages of sleep as the night goes on. As adults, our sleep cycles are longer, and when we wake up after a sleep cycle, we are typically able to fall back asleep quickly without any memory of waking up!
Babies, however, have shorter sleep cycles, and newborns especially can struggle with transitioning from one cycle to the next.
Within each sleep cycle there are many different stages (up to five depending on the age of your child).
Here are the five stages of sleep that babies experience:
Stage 1: This is really just a transition stage as babies first begin to fall asleep. Their eyes start drooping, possibly opening and closing a few times, and they can easily be woken up. This is why it is important to not try to transfer your sleeping baby into the crib during those first ten minutes - unless, of course, you are working on teaching your baby how to put themselves to sleep.
Stage 2: This is deeper than Stage 1, although still quite light sleep. Babies can still become easily started in this stage, and body functions begin to slow down.
Stage 3: This is a deeper stage of sleep that is hard to be woken from. Brain waves slow down and the body is usually completely still.
Stage 4: This is the deeper stage of sleep, where hardly any activity occurs. It can be very hard to wake up your baby during this stage! Stage 4 is typically experienced during the first half of the night, which is why many babies take their longest chunks of sleep between about 9pm and 2am (and then have those early-morning wake-ups!).
REM: Rapid Eye Movement (REM) sleep is the stage where more active movement happens, as that is when we (and babies) are dreaming. Newborns spend about 50% of their sleep in REM, with older babies spending just 30% there, and adults only about 20%. REM sleep plays an important role in learning, memory, and storing information in the brain.
Throughout the night, babies cycle through these stages, starting with stage 1, then stage 2, then 3, then 4, and then back down - 3, 2, and REM.
As babies transition from cycle to cycle, it is very common for them to become partially aroused. Adult cycles are about 90 minutes long, but baby sleep cycles are only about 40 minutes long. Some babies become fully aroused at this point and struggle to go back to sleep into another cycle, which is why many babies consistently take just 30-50 minute naps. These short naps don't mean that they are "finished" with their sleep! It just means they haven't learned to connect their sleep cycles and self-soothe. This is a common problem between 3.5 and 6 months.
So how can we help our babies connect their sleep cycles?
The best way to help your baby with this is to make sure they are not going down overtired! Awake windows that are too long are often a cause of short naps. When babies are put down overtired and continue taking short naps all day, they can become stuck in an overtired cycle and reject longer stretches of sleep in response to the exhaustion. Click here to see our recommended awake windows by age.
If this is the case and your baby is stuck in an overtired cycle, one way to help fix this is to do an “assisted nap.” Assisted naps are temporary solutions for babies 8-ish months and younger. By doing this you are helping extend a short nap by holding them, rocking them, etc. Again, this is not meant to be a long-term solution; rather, it is simply a way to help your baby get more sleep and break out of their overtired cycle. When practicing an assisted nap it should never be done when you are on the verge of falling asleep or by co-sleeping.
For all naps and nighttime, it is important to use blackout shades and a white noise machine. Both of these help keep your baby’s sleep environment consistent and non-distracting, which can definitely help keep baby in deep sleep for longer. For younger babies with an active Moro reflex, swaddling can also help baby feeling more secure and avoid unnecessary wake-ups.
As for nightime, in order for babies (and adults) to get their most restful sleep, they need to be able to enter night-sleep at the time that aligns best with their internal clock. By the time babies are 4 months old, they will start to move toward a 12-hour cycle, which means they are in bed 6pm-6am, 7pm-7am, or 8pm-8am. This means that if your baby wakes up at 6am for the day, the ideal bedtime would be 6pm. If bedtime is pushed too far after that, it might result in multiple night wakings or early risings (before 6am). This is why it is so, so important to follow age-appropriate awake windows and scheduling.
For multiple night-wakings, it may be that your baby is looking to you to help put her to sleep between every cycle. Sometimes this can be as simple as a quick pacifier replacement, but other times, for babies over 4 months, it may be time to work on teaching your baby to self-soothe.
For more detailed tips on connecting sleep cycles, see How to manage short naps and How to manage early-morning wake-ups.