1. How Many Hours a Day Do Newborn Babies Sleep?
In the first few weeks of life, babies are said to spend about 70% of their time sleeping. Since a day is 24 hours, this works out to roughly 17 hours of sleep. [2] Different sources may show slightly different numbers because they look at different ages or count time in different ways.
The National Sleep Foundation, a US expert group, lists recommended sleep times by age. For newborns (0–3 months), it is 14–17 hours. For infants (4–11 months), it is 12–15 hours. For toddlers, it is 11–14 hours, and for adults, it is 7–9 hours. The Foundation notes that these are ranges, and a person might be fine outside them if it suits their body. [1]
Another source explains that newborns and infants are awake for only about 10–30% of the day. Even at 30%, that is only about 7 hours of awake time in a 24-hour day. [5] If babies are awake for only part of the day, what is their brain doing while they sleep?
2. What Is Active Sleep, When Babies Twitch Their Eyelids and Limbs?
Sleeping babies sometimes twitch their eyelids or limbs. This type of sleep is called "active sleep" and is thought to correspond to REM sleep in newborns. [3] In healthy full-term newborns, more than half of their sleep is active sleep. [3]
Let’s look at the time. If a baby sleeps 14 hours a day, half of that is 7 hours. Since adults are recommended to sleep 7–9 hours a night, a newborn’s active sleep alone is about the same length as an adult’s whole night. [1] This is a calculation combining numbers from different sources, so treat it as a rough guide.
When limbs twitch, what is happening in the brain? Note that adult recommended sleep is 7–9 hours, so active sleep alone can match an adult’s night in this calculation.
3. Does a Baby's Brain Rest During Sleep, or Does Sleep Help It Grow?
Babies have short awake times and limited chances for strong stimulation. Yet, their brains grow rapidly. Researchers have considered that something during sleep might help this brain development. [5]
During active sleep, the brain has regular activity that happens naturally. Twitches are thought to trigger activity in the cerebral cortex, which may help develop senses and movement. [3] The idea that REM sleep helps brain development was a hypothesis proposed by Roffwarg and others in 1966, and testing continues today. [3]
Another source says REM sleep may help build early nerve circuits, while non-REM sleep may help organize them later. [5] However, we cannot yet say for sure that sleep helps brain development. We cannot experiment by taking sleep away from human babies, so this is a speculation that includes results from studies of animal babies.
4. Why Newborns Do Not Yet Sleep More at Night Than During the Day
Reports say that in the first few weeks, a baby’s sleep is spread almost evenly across the 24 hours. There is no strong tendency to sleep at night yet. [2]
One reason given is that the body clock is still immature. In newborns, the daily rhythms of hormones like melatonin and cortisol do not appear clearly. [2]
Medical manuals also state that in children aged 0–3 months, the circadian rhythm (body clock) is not established, and day-night reversal is not rare. [7] This shows that in the newborn period, the body clock is still developing, and sleep can be scattered across day and night. There is not just one reason for waking at night.
5. How Long Does It Take for Babies to Sleep Through the Night?
A report from 1984 observed babies for 6 months. They found that babies first create blocks of sleep and wake time, and then these blocks align with the 24-hour day-night cycle. The longest sleep gradually moves to darker hours. [6]
Regarding timing, infants usually adapt to a sleep schedule based on day-night cycles between 4 and 6 months of age. [7] Another source says that by 6–9 months, many infants can sleep for 6 hours or more at night. [2]
Individual differences are large. The time when cortisol rhythms appear ranges from as early as 2 weeks to as late as 9 months. [2] Sources do not support a fixed rule like "sleeps through the night at 3 months."
6. How Does the Amount of REM Sleep Change as Children Grow?
REM sleep makes up about 50% of sleep at birth. As children grow into toddlers and adults, this drops to about one-quarter. [4] The adult percentage varies by source, between 20% and 25%, so there is no single fixed number.
Sleep duration also changes with age. As noted earlier, the recommended sleep time for newborns is 14–17 hours, for infants 12–15 hours, for toddlers 11–14 hours, and for adults 7–9 hours. [1]
When you line this up, you can see that sleep changes in both length and content from baby to adult. REM sleep drops from about 50% at birth to about 25% in adults.
7. How Can You Learn About a Baby's Sleep by Asking Your Family?
You can ask your family what age you started sleeping through the night. It is okay if they do not remember. If they do, it can help you recall the range mentioned earlier: as early as 2 weeks or as late as 9 months. [2]
If there is a baby nearby and their guardian agrees, you can observe them sleeping from a distance, quietly. Do not touch or wake them. Watch if their limbs or eyelids move. Seeing movement does not prove it is active sleep, but you might feel that the body is active during sleep.
If you want to learn more, the link between baby sleep and brain development is still being researched. Reading hypotheses separately from proven facts changes how you see the topic. [3]
If a baby is nearby and the guardian gives permission, it is okay to observe their sleep quietly from a distance.