This is not a regression. It is a permanent, healthy leap forward in how your baby sleeps. Here is what is changing, and how to move through it with less panic.
Somewhere around three to four months, many babies who were sleeping in longer stretches suddenly start waking more again. Naps can turn short, and nights can feel harder than they did a few weeks ago.
Parents often call this the four month regression and worry they have lost their progress. You have not lost anything.
This is one of the most misunderstood moments in a baby's first year. Your baby's sleep is maturing into a more grown-up pattern, moving through lighter and deeper stages and briefly surfacing between cycles.
That surfacing is new, and until linking those cycles becomes familiar, your baby wakes all the way up and lets you know. This change is permanent, which means it is not a phase that reverses. It is a step forward in how your baby's brain sleeps, even though it arrives dressed as a setback.
Steady, predictable rhythms matter more now than any single technique. A calm and consistent wind-down tells your baby's body that sleep is coming.
If it fits your family, you can lay your baby down drowsy but still awake so that falling asleep starts to feel familiar in the crib.
Most of all, lower the pressure you put on yourself. Nothing you did caused this, and nothing you failed to do would have prevented it. Your job is to stay steady while your baby's sleep grows up.
A gentle note. This is warm, practical support, not medical care. For anything medical, feeding, weight, illness, or breathing related, please contact your pediatrician. Any sleep training approaches here are offered as choices along a spectrum from gentle to more structured, never as mandates. Your family, your call.