If your baby suddenly stopped sleeping the way they used to, you have not done anything wrong. Sleep regressions are a normal, temporary part of infant development that align with major developmental leaps.
When Regressions Typically Happen
Around 4 months, as sleep cycles mature and become more like adult sleep architecture. Around 8 to 10 months, alongside crawling and separation anxiety. Around 12 months, as walking and language development accelerate. Around 18 months, tied to the autonomy drive of toddlerhood.
Why They Happen
Each regression coincides with a genuine leap in brain development. The same neurological growth that produces a new skill, rolling, crawling, talking, temporarily disrupts the sleep patterns that were previously working. This is a sign of healthy development, not a problem to fix.
What Helps
Maintain your existing routine rather than abandoning it during the regression; consistency helps your baby find their way back faster. Offer extra comfort without creating new sleep associations you will need to undo later. Expect the regression to last 2 to 6 weeks in most cases, then resolve largely on its own.
What to Avoid
Do not introduce major new sleep props, like feeding to sleep every time, that you will need to remove later. Do not assume something is wrong; regressions are developmentally expected, not a sign of a sleep problem.
Related Guides
Baby Sleep | Babies 0-12 Months | Baby Routine