The circadian rhythm is our internal body clock. One of its role is to make us feel awake at certain times of the day and sleepy at other times. This means that we have windows of wakefulness throughout the day.  

Newborns have very short windows: they are awake for 45-90 min and need to sleep again. So that means that after eating, they may only have a few min before they get tired again! Over time, their windows get longer. By 4 mo, they usually can be up for 1.5-2 hours and by 6 mo, 2-3 hours.

When babies get to the end of their window and are naturally sleepy from a dip in their circadian rhythm, it’s easier for them to go to sleep. If we miss that window and they stay awake too long, then their body produces more cortisol, which is a hormone that is a mild form of adrenaline, which will keep them awake and going. That surge in cortisol is like having an espresso shot – it wakes up and keeps you going!! You know that “second wind” we refer to? Having that second wind usually means they are overtired.

When kiddos are overtired, it’s often harder for them to go to sleep (as you know, it’s hard to go to sleep after having an espresso!). Being overtired can also cause shorter naps, more frequent night wakings and earlier morning wake ups. So we really want to avoid overtiredness!


How do we do that?

Some babies give us signs that they are getting toward the end of their “window” and will need to go to sleep soon. We call those sleepy cues, and they will evolve as your child gets older Here are some common sleepy signs.

Here are some common sleep signs:

  • Yawning
  • Rubbing eyes
  • Red eyes
  • Slowing down
  • Looking away, lack of interest
  • Mild fussiness
  • Zoning out
  • Being clumsy
  • Not listening as well
  • Being cranky
  • Asking for milk, lovey, pacifier, etc.

When your baby starts to show their sleepy signs, it’s time to get ready for sleep. We want to catch them before they have a meltdown because they are so tired!

However, some babies do not give us any warning. If your baby is very alert, active and has FOMO (fear of missing out), there’s a good chance that they don’t show any signs of being tired until they are OVERTIRED! For those babies, we need to initiate sleep. Here’s how:

  • Instead of relying on his sleep signs, use the “clock”.
  • When she wakes up, set a timer for X min (see average wakeful windows below). This will remind you that it’s time for your baby to sleep again.
  • Even if baby does not look tired, go to a dark room, turn on the white noise and try to help them fall asleep.
  • Keep a sleep log for a few days to see the patterns. Adjust the timer based on that.


Getting to know your baby’s natural rhythm AND encouraging them to sleep BEFORE they get overtired is a gentle and effective way to improve sleep – and it works at all ages!

If you have any questions about your child’s sleep and would like more support, head over HERE to learn more about how we can work together to improve sleep. You can also join my free private Facebook group for sleep support.