Why Babies Sleep Differently
Newborns do not have an established circadian rhythm. Their suprachiasmatic nucleus (SCN) — the brain's master clock — is present at birth but not yet entrained to the light-dark cycle. It takes approximately 3–4 months for a meaningful circadian rhythm to establish, which is why "sleeping through the night" before 3–4 months is biologically unrealistic for most babies.
Infant sleep cycles are approximately 45–50 minutes long — roughly half the adult 90-minute cycle. Babies spend significantly more time in REM sleep than adults (50–60% vs 20–25%) because REM sleep is critical for the massive synaptic development occurring in infancy. Night waking at cycle boundaries is therefore completely normal and developmentally appropriate.
Month-by-Month Sleep Guide
0–1 month: 14–17 hours total in 2–4 hour stretches. No day/night distinction. Normal to feed every 2–3 hours. Survival mode — adult sleep will return eventually.
2–3 months: First signs of night preference emerging. May produce a 3–4 hour stretch once per night. Some differentiation between day (lighter, shorter naps) and night (longer stretches beginning).
4–6 months: Sleep consolidation begins. Many babies can produce 4–6 hour night stretches. This is the window to begin establishing a bedtime routine. A consistent 20-minute routine (bath → feed → sleep) produces measurable results within 1–2 weeks.
7–9 months: 2 naps per day (morning and afternoon). Night stretches of 5–8 hours become possible for many babies. Separation anxiety can emerge and disrupt established patterns temporarily.
10–12 months: Many babies consolidate to 2 naps, some begin transitioning to 1. Night sleep of 10–12 hours (with possible night waking) is typical. Consistent bedtime between 7–8 PM is recommended.
The Drowsy but Awake Principle
The most evidence-backed approach to teaching self-settling: put your baby down when drowsy but still awake — not fully asleep. This teaches the baby to fall asleep in the same environment they will wake to between cycles, reducing night waking when they naturally return to light sleep between 45-minute cycle boundaries.
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