Ask an Expert: Newborn and Infant Sleep – What is typical and what can sleep tell us about the developing brain?
Why does my baby wake so often? Why are they so noisy when they sleep? And when will they start sleeping for longer? We look at what research tells us about newborn sleep – and why scientists are interested in what happens in the developing brain while babies sleep.
Sleep is one of the biggest topics for families with a new baby – and often one of the most confusing.
Newborn sleep looks very different from adult sleep. Babies sleep in shorter stretches, wake frequently and can be surprisingly active while asleep. Their sleep also changes rapidly during the first weeks and months of life.
At INFANT, researchers also study sleep as a window into the developing brain. Here, we answer ten common questions about newborn sleep and explore what research is teaching us about sleep, brain development and babies who may need closer developmental follow-up.
What’s normal in the first few months?
Sleep varies considerably between babies. For babies aged 0–3 months, HSE guidance describes an average of around 14 hours in 24 hours, with a broad range of about 9–18 hours. These are general guides, not targets or a way to assess an individual baby’s health. Sleep is spread across the day and night, with frequent waking for feeds.
From our research
Research at INFANT through the BabySMART study used sleep diaries completed by parents of babies born at full term. Between four and 16 weeks, parent reported more night-time sleep, less daytime sleep and longer sleep episodes.
Newborn babies aren’t born with the same internal body clock as adults.
Our circadian rhythm helps regulate when we feel awake and sleepy. In newborns, this system is still developing, with a clearer day-night rhythm emerging during the first months of life.
As it develops, babies gradually begin to have more of their sleep at night and less during the day, although waking for feeds remains common. So those wide-awake-at-2am periods can be exhausting, but they are often part of early sleep development.
Sleeping babies can be surprisingly busy. They might twitch, move their arms and legs, change facial expression, grunt or make other noises.
Part of the explanation is active sleep, an early form of rapid eye movement (REM) sleep. Newborn babies spend a large proportion of their sleep in this state. During quiet sleep, babies tend to move less and breathe more regularly.
Research involving healthy newborns has found that organised patterns of sleeping and waking can already be seen within hours of birth. Sleep doesn’t necessarily mean a baby will be completely still and silent.
However, persistent grunting with breathing, very fast breathing or the chest pulling in under the ribs should not be dismissed as sleep noises. Seek urgent medical help if your baby is struggling to breathe.
There isn’t a particular age when every baby should start “sleeping through the night”.
In the early months, babies wake frequently to feed, and their sleep cycles and body clocks are still developing.
Research shows a gradual change rather than a single milestone. In the BabySMART study, babies’ longest uninterrupted stretch of sleep increased between four and 16 weeks.
There can still be considerable variation between babies, so one baby’s sleep pattern isn’t necessarily a useful benchmark for another.
What’s happening in a baby’s brain during sleep?
Sleep isn’t simply a period when a baby’s brain switches off.
The first months and years of life are a period of extraordinary brain development. Research suggests sleep is involved in processes important for brain maturation, learning and memory.
An INFANT-led review brought together 93 studies involving approximately 90,000 children to examine how sleep changes alongside early development. More recent research has explored relationships between infant sleep and areas including memory, language, movement and cognition.
Researchers are still learning about these relationships, but we know that sleep is an important part of early development – not something parents need to make “perfect”.
Yes – and this is where sleep becomes particularly interesting from a research perspective.
Researchers can use electroencephalography (EEG) to record the brain’s electrical activity using small sensors placed on a baby’s scalp.
Different patterns of activity can be seen during different sleep states. By studying these patterns, researchers can investigate how the brain is functioning and how this changes as babies grow.
So researchers aren’t only interested in how long a baby sleeps. What is happening inside the brain during sleep can also provide valuable information about early development.
Inside the research
INFANT researchers have studied brain activity during sleep from the newborn period onwards, including research describing typical sleep EEG in healthy babies. Understanding typical development provides an important foundation for investigating developmental differences.
What about babies who need closer development follow-up?
Babies born prematurely experience an important period of brain development outside the womb, sometimes while also experiencing illness or receiving neonatal care.
Researchers study how sleep and brain activity develop in these babies and whether there are differences compared with babies born at term. EEG is particularly useful because it allows researchers to observe patterns of brain activity while a baby sleeps.
This research may help us better understand early brain development in babies who could benefit from closer developmental monitoring.
It doesn’t mean parents should interpret differences in their baby’s everyday sleep as a sign of a developmental problem. The patterns researchers investigate require specialist measurements and clinical assessment.
Potentially – and this is an emerging area of research.
One INFANT study recorded babies’ brain activity during sleep at four months and followed their development to 18 months. Researchers found associations between some features of sleep EEG and aspects of later neurodevelopment.
This suggests the sleeping brain may contain information that can help researchers understand early development.
But an association in research is not the same as predicting an individual child’s development. Sleep EEG is not currently a test that can predict a baby’s developmental outcome. More research is needed to understand whether these measures could eventually help identify babies who may benefit from closer monitoring or earlier support.
From our research
INFANT researchers are investigating whether features of brain activity recorded during infant sleep could help us better understand early neurodevelopment.
What should parents know?
In the early weeks, focus on your baby’s need for feeding, comfort and sleep. Newborns are too young for a strict sleep schedule.
Newborn sleep is still developing and waking to feed is normal. As babies get older, their day-night rhythm gradually begins to mature.
Simple cues such as natural light and normal household activity during the day, and a quieter and darker environment at night, can help support this developing rhythm.
Every baby develops differently, so families shouldn’t feel under pressure to achieve a particular sleep routine or compare their baby’s sleep with someone else’s.
Safe sleep: what every family should know
Whatever your baby’s individual sleep pattern, a safe sleep environment is important for every sleep, day and night.
Current HSE guidance recommends putting babies on their back for every sleep, using a firm, flat mattress, keeping their head and face uncovered and keeping pillows, cushions, cot bumpers, toys and loose or bulky bedding out of the cot.
Babies should be protected from overheating and cigarette smoke and sleep in their own cot in the same room as their parent or caregiver for at least the first six months.
Safe-sleep advice may differ in some circumstances, including for babies born prematurely or with particular medical needs. Families should follow advice from their healthcare team.
For current Irish guidance, visit the Health Service Executive (HSE):
- Newborn sleep needs: 0–3 months – what to expect from newborn sleep.
- Cot death (SIDS): reducing the risk – current recommendations for reducing the risk of cot death.
- Safe sleeping position – guidance on putting your baby on their back for sleep.
- Where your baby should sleep – information on cots, mattresses, room sharing and other sleep environments.
- Your baby’s sleep temperature – advice on clothing, bedding and avoiding overheating.
- Caring for a premature baby at home – information for families of babies born prematurely.
The research behind this article
Research at INFANT Research Centre, University College Cork, is helping us understand how sleep and brain activity develop from the newborn period onwards, in healthy infants and in babies who may benefit from closer developmental follow-up.
Research referenced in this article includes studies of newborn sleep-wake patterns, the BabySMART infant cohort, sleep EEG and early neurodevelopment, and reviews of sleep and development during infancy.
References
- O’Sullivan MP et al. Reference centiles for infant sleep parameters from 4 to 16 weeks of age: findings from an Irish cohort. Archives of Disease in Childhood, 2023.
- Korotchikova I et al. Sleep-wake cycle of the healthy term newborn infant in the immediate postnatal period. Clinical Neurophysiology, 2016.
- Lenehan SM et al. The Architecture of Early Childhood Sleep Over the First Two Years, 2023.
- Ventura S et al. Infant sleep EEG features at 4 months as biomarkers of neurodevelopment at 18 months, 2025.
- O’Connor C et al. Sleep and infant development in the first year. Pediatric Research, 2026.
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INFANT’s Ask an Expert series takes questions from families and explores what research can tell us about pregnancy, babies and children’s health.
