How baby sleep works
Your baby's sleep is part of their physical development, just like learning to walk and talk.
The maturing of your baby’s sleeping and waking cycles is one of their most important developmental tasks.
Sleep is important for many parts of a baby's development. It helps with brain maturation, learning, memory, social skills, and physical health.
Circadian rhythms
One of the biggest influences on baby sleep is the circadian rhythm, the natural 24-hour day-night body clock. Light and dark, body temperature, and the hormone melatonin influence the circadian rhythm and support sleep.
In the first four weeks, many babies do not have a clear day and night pattern. They wake to feed every 2 to 4 hours around the clock. Over the next few months, your baby will be more awake during the day and begin to build longer sleep periods overnight.
Your baby’s day-night rhythm
Your baby’s biological clock functions best when you align it with natural light and natural darkness.
Daylight helps your baby stay alert during the day, but darkness does not always make a young baby sleep straight away. This is normal and is one reason why settling can feel difficult in the early months.
As the day and night cycle becomes familiar, many babies develop a pattern of waking early in the morning, and becoming fussier in the late afternoon and evening. This is developmentally normal, and is also influenced by breastmilk supply. Understanding these patterns along with observing your own baby’s communication cues, can help you plan routines that support baby sleep.
The role of light
Light is one of the most powerful tools you have to support baby sleep. Natural daylight in the morning and early afternoon helps regulate your baby’s body clock and daytime alertness.
On the flipside bright artificial light at night can delay the development of your baby's natural circadian rhythms and extend the length of the day. Evening exposure to screens and strong indoor lighting can be especially stimulating.
Keeping the environment calm and dim at night helps create a clear difference between day and night. This supports better sleep over time.
How melatonin and body temperature work
Melatonin is a naturally produced hormone that encourages sleep and is produced at night. In typically developing children in the first weeks of life, baby’s melatonin levels are supported through feeding, with hormonal regulation being developed by around 10 to 12 weeks of age.
Body temperature is important too. As sleep gets closer, melatonin increases and body temperature goes down. This helps your baby feel sleepy and fall asleep.
You can support this process by creating a predictable night-time routine with dim lights.
External daily rhythms
Baby sleep is also shaped by daily patterns around feeding, activity, and social connection.
Daytime is for social time, active feeding, and interaction. Night-time is for quiet feeding, low stimulation, and returning to sleep.
Over time, this consistent pattern helps your baby learn the difference between day and night and supports longer sleep stretches.
Young babies sleep in short cycles (often around 40 to 50 minutes). Learning to connect sleep cycles is another learning step that occurs over time.
Feeding, socialising and activity patterns
Feeding is a great way to help your baby sleep better. It helps set a routine for day and night and contributes to the developing relationship between you and your baby.
During the day, feeding can be a social time. It helps your baby stay awake to eat well. This also builds a connection that supports brain development.
At night, use soothing touch, speak in quiet tones and keep lights dim. You may have been told not to make eye contact with your baby at night, this isn't true. Eye contact is important for love and reassurance.
A predictable flow to the day helps your baby feel safe and supported, but flexibility is important because your baby will sleep when tired and feed when hungry, not by the clock.
How Tresillian can help with baby sleep
At Tresillian, we help thousands of Aussie parents with their children's sleep challenges. From babies who can't settle themselves independently, to those that are learning to link sleep cycles and to helping parents recognise their baby’s sleep signals.
Here you’ll find our top baby sleep advice when your baby won't sleep. We’ll show you how to recognise baby’s ‘tired’ signs or cues and advice on settling techniques for different age-groups such as newborn, 3-6 months, 7- 12 months and beyond into toddlerhood.