• Midline is an imaginary vertical line that divides the body into left and right halves. Crossing midline involves reaching across this line with arms or legs, and it indicates a developing connection between the brain’s hemispheres.

• Babies typically begin to cross midline by bringing hands to their mouth (2-4 months), reaching for their feet (4-6 months), and reaching for toys while lying on their back or tummy (2-6 months).

• Activities like Tummy Time and the side-lying position can encourage midline crossing. If Baby has trouble with these movements by 6 months, consult a healthcare provider.

“Crossing midline” might not be a term you say every day, but it’s something you do all the time! When you tie your shoes, get dressed, or exercise, you might cross midline many times. Learn more about what crossing midline means, and why it’s so important for Baby!

What is midline?

Midline is an imaginary vertical line that divides the body in half. It’s the line that determines if things are on the left side or right side of your body.

What does it mean to cross midline?

Any time you reach over the imaginary midline of your body with your arms or legs, you cross midline. Put your hands out in front of you and move the right hand to touch the left. You just crossed midline!

When Baby crosses midline, they may do this by bringing their hands together (such as when they clap!), reaching for their feet, or reaching for a toy on their side.

Why is it important for Baby to cross midline?

While crossing midline may seem simple, for Baby, it’s a sign of a strengthening connection between the left and right sides of the brain. This is known as bilateral coordination (or bilateral integration), and helps Baby do things like crawl and walk!

Crossing midline requires coordinating different skills and parts of the body. In fact, in order to cross midline, Baby must have:

• Some control over their arm and leg movements

• Developing body awareness (known as proprioception)

• Hand-eye coordination

• Strengthening brain communication

When will Baby cross midline?

As Baby’s early motor skills develop, they will slowly work up to crossing midline. Look for these signs that Baby is crossing midline!

• Baby brings hands to midline. This typically happens around 2-4 months, and you'll see it when Baby brings their hands to their mouth. A great way to encourage hands to midline is by doing the side-lying position!

• Baby brings hands to feet. This is a 4-6 month milestone. Learn how to help Baby do it in the video below!

• Baby reaches for toys. By 4 months, Baby will attempt to reach for a toy held above their chest while lying on their back. As they get better at reaching, Tummy Time, and holding their head up, they’ll begin to reach for nearby toys while on tummy, which usually means crossing midline! This happens around 4-6 months.

To help Baby bring hands to midline, try presenting a toy to Baby at midline. Watch how Baby brings it to their mouth and moves the toy in midline!

How can I help Baby learn to clap?

Clapping is a great way to bring hands to midline! Baby learn to clap because they see their caregiver doing it. So one of the best ways to help Baby learn to clap is by clapping yourself! Clap when:

• Playing together and having fun

• Praising Baby for something they did

• After completing a task (like eating or reading a book)

• Singing a song or dancing

• Celebrating!

You can also play games that involve clapping with Baby! Our pediatric physical therapists recommend:

• Pat-a-cake: This classic nursery rhyme involves clapping. When Baby can start sitting up on their own (around 4-6 months), help them clap their hands together while singing the rhyme.

• Peek-a-boo: Clap when appearing after peek-a-boo or when Baby tries to find you.

• Baby See, Baby Do: Sit across from Baby, facing them. Say: “Do what I do!” Make a funny face, stick out your tongue. Clap when they copy you. Use other parts of your body as well – hands, arms – encouraging them to do what you do. (This game is recommended for Baby at 12-15 months).

If Baby seems to have trouble coordinating their body movements or crossing midline by 6 months, speak to a healthcare provider to learn more!