What Causes Split Nights in Babies (And How to Fix Them)

So first off, what is a split night?

A split night is when your baby or toddler wakes in the middle of the night for a long stretch—sometimes up to a few hours—and struggles to go back to sleep. During this wake-up, they might be upset and hard to settle, or they might be bright-eyed, chatty, and ready to party (even though you're not!).

Understanding why split nights happen can help you find the right solution—and the good news is, it's usually a temporary phase.

What Causes Split Nights?

Split nights are typically due to a disruption in your child’s sleep pressure or circadian rhythm. Babies (and adults too) need a certain amount of sleep in a 24-hour period—usually 10–13 hours overnight for little ones, plus naps during the day. If that balance is thrown off, your baby may wake fully in the middle of the night while their body waits to rebuild enough sleep pressure to fall back asleep.

Contrary to what you might assume, split nights often don’t require “sleep training.” If your baby knows how to fall asleep independently, the issue likely lies with timing or nap structure.

Let’s break down the most common causes and what you can do to help.

1. Under-tiredness (Too Much Daytime Sleep)

If your baby is napping too much or for too long, their body might not be ready for a full stretch of overnight sleep. You might notice your baby is completely happy during the long waking—cooing, babbling, rolling around.

What to do: Take a look at your baby's nap schedule and awake windows. Are they ready to drop a nap or stretch their wake times a bit? This blog post on when to drop a nap is a great place to start.

2. Overtiredness (Not Enough Daytime Sleep)

Yep, the opposite problem can cause the same issue. If your baby is skipping naps or staying up too late, their body might produce more cortisol (the stress hormone), which makes it hard to fall and stay asleep. These babies are usually not so happy during the night—they’re fussy, crying, and clearly overtired.

What to do: It can be tricky to tell the difference between under- and overtiredness. That’s why I wrote this blog to help you tell the difference between over- and under-tiredness. If you’re dealing with overtiredness, this blog on breaking the overtired cycle is a must-read.

3. Developmental Milestones (aka Sleep Regressions)

Is your baby suddenly practicing new skills in the middle of the night—rolling, sitting, crawling, or even standing? This could be a developmental sleep regression.

What to do: These regressions are completely normal and often pass on their own, but support and consistency can help ease the process. My free Sleep Regression Mini Course walks you through what’s happening and how to ride it out.

4. Chronic Short Naps + Very Early Bedtime

I’m all for an early bedtime (6:00–8:00 PM is golden), but when naps are short and bedtime creeps earlier and earlier, it can mess with your baby’s circadian rhythm. Bedtimes before 6:00 PM, combined with 2–3 short naps, can lead to early morning wake-ups or—you guessed it—a split night.

What to do: Work on extending your baby’s naps first. This will help balance their sleep pressure throughout the day. Start with this blog: 5 Tips for Short Naps. And if you’re ready for a plan that actually works, my Ultimate Nap Guide has everything you need.

You’re Not Alone (And You’ve Got This)

Split nights can feel exhausting and confusing, but they are fixable with a little troubleshooting. With some gentle schedule tweaks and support, you’ll be back to consolidated sleep soon.

And if you need a step-by-step plan? That’s what I’m here for.

👇 Choose your baby’s age and get a sleep strategy that fits your parenting style:

• Sleep help for babies under 3 months
• Sleep help for babies 4–24 months
• Sleep help for toddlers 2+ years

 
Citations:

Jenni, O.G. and LeBourgeois, M.K., 2006. Understanding sleep–wake behavior and sleep disorders in children: the value of a model. Current opinion in psychiatry, 19(3), p.282.

Cooney, M.R., Short, M.A. and Gradisar, M., 2018. An open trial of bedtime fading for sleep disturbances in preschool children: a parent group education approach. Sleep medicine, 46, pp.98-106.

Wurts, S.W. and Edgar, D.M., 2000. Circadian and homeostatic control of rapid eye movement (REM) sleep: promotion of REM tendency by the suprachiasmatic nucleus. Journal of Neuroscience, 20(11), pp.4300-4310.

Lee, M.L., Swanson, B.E. and Horacio, O., 2009. Circadian timing of REM sleep is coupled to an oscillator within the dorsomedial suprachiasmatic nucleus. Current Biology, 19(10), pp.848-852.

Khalsa, S.B.S., Conroy, D.A., Duffy, J.F., Czeisler, C.A. and DIJK, D.J., 2002. Sleep‐and circadian‐dependent modulation of REM density. Journal of sleep research, 11(1), pp.53-59.

Czeisler, C.A., Weitzman, E.D., Moore-Ede, M.C., Zimmerman, J.C. and Knauer, R.S., 1980. Human sleep: its duration and organization depend on its circadian phase. Science, 210(4475), pp.1264-1267.