4-month regression playbook
Want the other 11 too? Email yourself the full bundle — we'll send updates when any sheet gets revised.
4-month regression playbook.
It's not a regression — it's permanent maturation of sleep architecture. Mature cycles + new wake-window length = the disruption you're seeing. Here's what to do, what to avoid, and the timeline.
Until ~4 months, babies sleep in 2 stages (active + quiet). Now they shift to 4 stages including REM and deep NREM — adult-style sleep architecture. They wake fully at the end of each ~45-min cycle and have to learn to resettle without help.
2-6 weeksfor most. The architecture change is permanent; the disruption is temporary. By 5-5.5 months, babies who’ve learned to link cycles independently sleep longer stretches than they did before the regression.
| Mistake | Why it backfires | Do this instead |
|---|---|---|
| Adding a feed at every wake | Reinforces feed-to-sleep association at exactly the moment baby is learning to link cycles independently. Feed becomes the only resettle tool. | Feed once or twice a night max if needed. Use a brief presence + pat-shush at other wakes. |
| Earlier bedtime to “catch them up” | Bedtime is already approximately right. Earlier = waking earlier in the morning, which fragments the night further. | Hold bedtime steady. If overtired, bring it 15 min earlier — not 60. |
| Bringing baby to your bed | Hard to undo once started; AAP advises against bed-sharing with infants under 12 months for SIDS reasons. | Pull crib into your room (room-sharing recommended through 6-12 months) — gives proximity without the safety risk. |