Totally normal (and totally exhausting). 4–5am is a “biologically light” time for babies, so little things wake them. Here’s why it happens and what you can do.

What’s causing the 4am wake?

• Circadian biology: Around 3–5am, cortisol rises and melatonin drops; body temperature is at its lowest. Sleep is light and easily disrupted.
• Sleep pressure is gone: If your baby went down early, they may have already had 10–11 hours—many babies’ typical night max—so their body thinks it’s morning.
• Hunger/diaper/discomfort: Especially <6–7 months or during growth spurts.
• Environment: Dawn light leaking in, birds/garbage trucks, or the heat kicking on.
• Schedule mismatches:
  • Too late bedtime → overtired → early rising.
  • Too early bedtime or too much day sleep → they’re done by 4–5am.
  • First nap too early → body clock shifts earlier.
• Development/teething: New skills (rolling, crawling, standing) often show up at dawn.
• Sleep associations: If they need help falling asleep at bedtime, they’ll often need the same help at 4am.

Quick fixes that actually help

• Black out the room (truly dark) + steady white noise all night.
• Room temp: Aim ~68–72°F (20–22°C); avoid being too warm.
• Treat anything before 6:00am as night: low lights, few words, brief feed/diaper, back down.
• Shift the schedule (pick one, try for 5–7 days):
  • If nights are short (<10h) or bedtime is late, try an earlier bedtime by 15–30 min.
  • If nights are already 11–12h and bedtime is early, push bedtime later by 10–15 min every 2–3 nights.
• Guard the first nap: Don’t start it too soon after that early wake, or the body clock “locks in” 4am. Try:
  • 4–6 mo: first nap ~2–2.5h after wake
  • 6–9 mo: ~2.5–3h
  • 9–14 mo: ~3–3.5h
  • 14–18+ mo: ~4–5h
• Right-size total day sleep: Rough ballpark (varies by baby):
  • 4–6 mo: 3–4h over 3 naps
  • 6–9 mo: 2.5–3.5h over 2–3 naps
  • 9–14 mo: 2–3h over 2 naps
  • 14–24 mo: 1.5–2.5h (1 nap)
    Too much day sleep = earlier mornings.
• Feeds: <6–7 mo or if weight gain is a focus, a later evening feed (“dream feed” around 10–11pm) can stretch mornings for some babies.
• Independent settling: Practice at bedtime; it often pays off most at 4–5am.

When it’s a red flag

• Loud snoring, gasping, chronic mouth-breathing, frequent night sweats, poor weight gain, severe reflux, or constant inconsolable wakes—check with your pediatrician.

If you share your baby’s age, bedtime, nap lengths/times, and what you do at 4am, I’ll map out a 7-day tweak plan tailored to you.