Why Is My Baby Having Trouble Falling Asleep?

Parents often hear about the importance of avoiding an “overtired” baby, but undertiredness can cause just as many sleep struggles. Knowing the difference can help you respond more effectively to your baby’s needs and avoid unnecessary bedtime battles.

Understanding Sleep Pressure

Babies, like adults, have a natural drive to sleep called sleep pressure, which builds the longer they’ve been awake. If bedtime comes too soon, there isn’t enough sleep pressure, and the baby may resist sleep — that’s undertiredness. If bedtime comes too late, the baby’s body produces stimulating hormones like cortisol and adrenaline, making it harder to fall asleep — that’s overtiredness1.

Signs of an Overtired Baby

Research shows that when babies stay awake past their ideal wake window, they experience increased stress hormones, making them harder to soothe2. Signs include:

• Fussiness or crankiness despite being held or fed

• Red eyelids or eyebrows

• Pulling at ears or rubbing eyes

• “Second wind” energy or sudden hyperactivity

• Short, restless naps or frequent night wakings

A 2011 study in Early Human Development found that prolonged wakefulness in infants correlates with shorter total sleep duration and more fragmented nighttime sleep3.

Signs of an Undertired Baby

Undertiredness is often overlooked because it can look like “not sleepy yet.” Signs include:

• Playing or babbling in the crib

• Rolling around or crawling instead of sleeping

• Crying immediately when put down, but calming quickly if taken out

• Taking a long time to fall asleep despite being in bed
  

A 2020 study in Sleep Health found that infants placed in bed before reaching sufficient sleep pressure took significantly longer to fall asleep and were more likely to resist bedtime4.

Ideal Wake Windows by Age

Wake windows — the amount of time a baby can comfortably be awake — change as your child grows. While every baby is different, research-supported averages are:

• 0–3 months: 45–90 minutes

• 4–6 months: 1.5–2.5 hours

• 7–9 months: 2–3.5 hours

• 10–12 months: 3–4 hours5

Tracking your baby’s wake times for a week can reveal patterns and help you find their sweet spot for sleep.

How to Strike the Right Balance

1. Observe your baby’s cues – Combine clock-based wake windows with behavioral signs.
   

2. Avoid extremes – If naps are too short, bedtime may need adjusting earlier; if your baby plays for long periods in the crib before sleeping, try extending wake time.
   

3. Stay consistent – Research shows babies with consistent nap and bedtime routines fall asleep faster and have better nighttime sleep quality6.
   

Need More Help?

If your baby is not falling asleep independently within 5-10 minutes in the crib and is still waking up multiple times in the night, a baby sleep plan can take the guesswork out of your baby’s sleep puzzle. These plans share age-appropriate schedules and step-by-step instructions for your little one to properly balance their hormones and help them sleep 10-12 hours each night independently.

Footnotes

1. Mindell, J. A., & Owens, J. A. (2022). A Clinical Guide to Pediatric Sleep. Wolters Kluwer. ↩

2. Bathory, E., & Tomopoulos, S. (2017). Sleep regulation, circadian rhythm, and melatonin in infants. Pediatric Annals, 46(4), e133–e138. ↩

3. Sadeh, A., et al. (2011). Infant sleep predicts attention regulation and behavior problems at 3–4 years. Early Human Development, 87(8), 629–633. ↩

4. Burnham, M. M., et al. (2020). Infant sleep timing and parental sleep duration. Sleep Health, 6(1), 71–77. ↩

5. American Academy of Pediatrics. (2023). Healthy Sleep Habits: How Many Hours Does Your Child Need? ↩

6. Mindell, J. A., et al. (2015). Bedtime routines for young children: A dose-dependent association with sleep outcomes. Sleep, 38(5), 717–722. ↩