Why does your baby sleep badly during a Wonder Weeks leap?

It was going so well. And then, out of nowhere, your baby is awake three times a night again.

Often there's a leap behind it. Many parents know it from the book The Wonder Weeks: ten mental leaps in the first twenty months.

When each leap comes

Kyra's own overview, with what changes in each leap and what it does to the night:

• Leap 1, around 5 weeks. The world of sensations.
• Leap 2, around 8 to 9 weeks. Discovering patterns, and the moment to start a bedtime routine.
• Leap 3, around 12 weeks. Smooth transitions, and the end of swaddling comes into view.
• Leap 4, around 15 to 19 weeks. Cause and effect, together with the four-month sleep regression. The hardest one.
• Leap 5, around 26 weeks. Understanding relationships, and the first separation anxiety.
• Leap 6, around 37 weeks. Categories, crawling and sitting, stronger separation anxiety.
• Leap 7, around 46 weeks. Sequences and steps, and practicing standing.
• Leap 8, around 55 weeks. Plans and goals, and the turning point.

Leap 9 is about understanding principles and rules, leap 10 about systems, more complex play and the start of language. Kyra gives no age for those, and that's no accident: from leap 8 onwards, the leaps affect sleep much less. More on that below.

Why sleep suffers so much

With every leap, the brain makes new connections, and afterwards your baby sees the world differently than the day before. Everything that comes in has to be processed again, and that takes an enormous amount of energy.

There's something else. Babies want to practice a new skill, and that practice doesn't stop at bedtime. They simply carry on in bed. Rolling, making little sounds, busy with their hands.

More to process plus more practice means waking up more often.

The three C's

Are you in one? Look for these three, which usually come together:

• Crying, more than you're used to
• Clinginess, wanting to be held all day
• Crankiness, frustrated faster, overstimulated faster

See all three at once, and most likely nothing is broken: you are in a phase.

Which leaps hit sleep hardest

Not all ten affect sleep equally, and the rule behind it is simple: it's the leaps that coincide with a motor milestone. Rolling in leap 4, crawling and sitting in leap 6, standing and walking in leap 7.

It makes sense: those are exactly the skills that can be practiced in bed. From leap 8, the focus shifts to thinking, planning and language, and those aren't practiced lying down in a crib.

What to do at night, and during the day

Give extra closeness. During a leap, your baby needs more security than usual. Extra skin-to-skin, extra cuddles, and the baby carrier during the day. You're not teaching anything wrong; you're helping your baby through a phase.

Protect the basics. Darken the room, because a brain running at full speed has less to process in the dark. Keep the bedtime routine exactly as it was. Precisely when everything wobbles, that fixed part is worth it.

Watch out for new sleep associations. This is the tip that gets skipped most often. If feeding or rocking at every night waking wasn't needed before, don't start doing it automatically now. Otherwise, in two weeks you build a habit you'll have to undo afterwards.

Let your baby practice during the day. With enough room for the new skill during the day, there's less to catch up on at night.

And postpone plans. Were you about to start sleep coaching or night weaning? Wait until this has passed.

It's a phase, and that's literally true

A leap builds up, peaks and fades. Sleep comes back afterwards, usually within a few weeks. Knowing that doesn't help much in the middle of the night, true. At four in the afternoon, it does.

Besides the mental leaps, motor milestones play a part too: sitting, crawling and sleeping badly.