If your baby has previously been able to sleep through the night but now suddenly not only wakes up but also stays up for a couple of hours, you are looking at what we call "split nights".
Split nights can be extremely frustrating, and sometimes hard to deal with once you enter the perpetual cycle of lengthy wake-ups overnight, late mornings and naps that are out of whack.
But there are a couple of things we can do if we can pinpoint what is causing your child's midnight parties.
Have they had too much day sleep?
Did they go to bed too early?
Or did they go to bed too late??
I know, that just sounds downright confusing, doesn't it?
When it comes to sleep, there are two main components that dictate how easily we can fall asleep and stay asleep - our circadian rhythm and sleep pressure, also known as 'homeostatic sleep drive'.
Our circadian rhythm is our build-in body clock, the one that lets you wake up at roughly the same time every morning, that tells you it's lunchtime and when it's time to go to bed.
The homeostatic sleep drive describes our need to sleep and slowly builds throughout the day. You want to hit your baby's sweetspot when it comes to bedtime and make sure there is neither too little nor too much sleep pressure. If your baby has had too much day sleep, they simply don't need enough sleep overnight, leading to a confused body clock and overnight parties. If they had too little sleep, they could be overtired which can lead to your baby's body producing cortisol which also hinders sleep. If your baby's circadian rhythm and homeostatic sleep drive are out of sync your baby will most likely be able to go to sleep but then wake fully refreshed after a few hours.
How can you fix your baby's 'split nights'?
The first thing I suggest you do is decrease the amount of sleep your child is having during the day. If they are still napping, decrease the length of their nap progressively until you see a change in their overnight sleep.
Alternatively you could push back bedtime in 15 minute increments until you hit that sweetspot again. When doing this, it's important to make sure your baby isn't getting overtired.
When it comes to the actual overnight wakeups, a lot of children are actually quite happy and often just babble to themselves, rather than needing to be resettled. Make sure you don't accidentally reinforce split nights, by turning these wakeups into playtime. Keep the lights off or very dimmed and avoid giving food (unless your child is still young enough to require a feed overnight).
In the morning, make sure you wake your child at their normal wake-up time, as a sleep-in can actually exacerbate split nights. We want to build more sleep pressure during the day, so letting them catch-up on lost sleep is actually counter productive.
Fixing split nights isn't usually done overnight, so hang in there.