Why does your baby sleep so badly in Wonder Weeks leap 4?

Kyra marks this leap in her overview in a different color on purpose. Of the ten, this is the one where sleep suffers most, and there's a reason it's this one in particular.

Two things at once

Leap 4 is about cause and effect: the discovery that actions cause reactions. There's a lot of practice with rolling, moving and grabbing.

And in exactly the same weeks, the sleep structure itself changes. The sleep cycle starts to resemble an adult's, with a light moment at the end of every cycle. That's the four-month sleep regression, and that article has the step-by-step plan.

The two come together, and that's why this feels different from the leaps before. There isn't one thing going on but two, and they reinforce each other.

Why practice is the problem

What gets learned during the day gets repeated at night. With a leap about movement, that literally means practicing in bed: rolling, turning, getting stuck on the tummy with no way back.

That's why Kyra links the hardest leaps to the motor milestones rather than the mental ones. See rolling over and sleep for what to do about it in practice.

What to do in this leap

Practice the movement during the day, every day. That's the shortest way out of the in-between phase.

Stop swaddling as soon as the first signs of rolling appear. From that point, sleeping swaddled is no longer safe: how long you can swaddle.

And postpone new plans. This isn't the moment to start sleep coaching or to wean night feeds.

Leap 4 symptoms: how to tell you're in it

By the three C's: more crying, clinginess, crankiness. The full approach is in Wonder Weeks and sleep.

Before this came leap 3, and around twenty-six weeks, leap 5 follows.