To understand more about a baby’s sleep, read the first part of this article, Demystifying Baby Sleep from Birth to One Year.

Photo - Horloge pour illustrer les cycles de sommeilUpdated article July 2021

Before helping a baby sleep properly, it’s important to learn about sleep physiology and cycles of a young child.

A sleep cycle can last from 45 minutes to two hours based on age. For an infant, it’s about 50 minutes and can be repeated up to 10 times a night. Only around three years of age can we expect them to have sleep cycles like adults.

Unfortunately, sleep regulation maturity takes time, is a gradual process that can’t be fast-forwarded. We have our own pace of development, such as walking for example.


Sleep cycles are made up of four phases:

  1. Light sleep;
  2. Deep sleep;
  3. Paradoxical sleep;
  4. Latency phase.
  1. Light sleep:
    In this phase, the baby moves a lot, is uncomfortable, groggy.
  2. Deep sleep:
    Metabolically, this sleep phase is characterised by an increased release of hormones needed for the baby’s growth. It also strengthens its immune system which helps combat microorganisms. Heartbeat and respiration slow. This is the calmest sleep. Even if this is the deepest sleep, the baby can maintain its muscle tone, closing its fist, for example.
  3. Paradoxical sleep:
    Compared to a three-year-old baby, who will spend 25% of their sleep in this phase, a baby will spend 50% to 80%. Has anyone used the saying “sleeping like a baby?” Sure, right! In the paradoxical sleep phase, the baby’s eyes move, they may cry out, they may make sucking movements, or their muscles might jerk. This is associated with high brain activity. Their neurological development depends on this stage and it helps them store everything they learned when awake. Their brain is working hard even if you find their sleep troubled.
  4. Latency phase:
    The latency sleep phase brings us back to the surface, close to awakening. It’s like a state of drowsiness, a very shallow sleep. Many babies can ask for something in this phase, or slowly fall back into the light then deep phases. This is the phase between the two cycles.

You now know more about how your baby’s sleep functions.

To continue reading, go to How to help your baby’s sleep?

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