What happens in Wonder Weeks leap 3, and what changes about sleep?

This leap often gets skipped in stories about sleep, and that's a shame, because something disappears that has partly shaped the nights until now.

What changes in this leap

Leap 3 is about smooth transitions. Movements become fluid instead of jerky, there's more control over arms and legs, and an interest in toys appears.

Kyra names one thing explicitly: there's less startling. Coordination between the parts of the body increases.

What that does to the night

The startle reflex, the Moro reflex, is one of the reasons a young baby wakes up all by themselves: the little arms shoot up and sleep is gone. That's exactly what swaddling helps with.

When that reflex fades, part of the reason to swaddle fades too. And the movements that take its place are the groundwork for rolling over, which comes one leap later.

So this is the month to know where the line is: stop swaddling at the first signs of rolling, not later. See how long you can swaddle.

What to do in this leap

Practice the movement during the day. What gets practiced during the day doesn't need to be figured out at night anymore. See how much tummy time a baby needs.

And if what used to help suddenly stops working, in these weeks that's not a setback but progress: old tricks no longer work.

Leap 3 signs: 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 2. Next comes the hardest of them all: leap 4.