4‑month sleep regression: what it is and what to do

Somewhere around 3 to 5 months, sleep just falls apart. Naps shrink, nights get choppy, and nothing you did last week seems to work anymore.

You don’t need to fix everything at once. Lock down bedtime, keep wake windows reasonable, and give it 7 to 10 days before rethinking your whole approach.

What's happening (in plain language)

• Sleep becomes lighter and baby may wake more between cycles.
• Wake windows can shift quickly (what worked last week may be too long today).
• Daytime naps often get shorter, which can cascade into an overtired bedtime.

Your 3 priorities (keep it simple)

1) Protect bedtime

• Keep bedtime in a consistent range.
• Use a calm routine with the same order every night.
• If naps were messy, earlier bedtime is often better than "stretching".

2) Avoid overtiredness (don't aggressively stretch windows)

At this age, many night waking spirals come from being just a little too awake for too long, especially late afternoon.

3) Make one small change at a time

• Pick one wake window to adjust (often the last one).
• Change by 10–15 minutes.
• Hold it for 2–3 days before changing again.

A practical 7‑day plan

• Days 1–2: Keep wake-up time and bedtime steady; don't chase perfect naps.
• Days 3–4: Adjust the last wake window slightly earlier or later based on settling time.
• Days 5–7: Optimize one daytime nap (often the first nap) by adjusting only the wake window before it.

Troubleshooting

Baby wakes 30–60 minutes after bedtime (false start)

• Often overtiredness → try an earlier bedtime for 2 nights.
• Keep the routine calm; avoid adding stimulation.
• Re-check the last wake window.

Naps are suddenly short

• Shorten the next wake window by 10 minutes.
• Stabilize the sleep space (dark, cool, consistent).
• Don't "pay back" with a late bedtime—protect bedtime.

Night wakings increased

• Return to your last "okay" baseline for 2–3 days.
• Look for overtired patterns: short naps + long windows.
• Track trends for a week, not one night.