What is it and how to test it


Have you ever wondered why your newborn baby’s arms are always up while sleeping? Here’s what you need to know about the tonic neck reflex in babies.

In this article you will read:

  • Tonic neck reflex in newborns
  • How to check the tonic neck reflex?
  • Until when is this normal?

Do you ever see your newborn lying on his back looking like a fencer getting ready with his sword? It may sound weird, but it’s just one of the many reflexes your baby has. These fun poses actually mean your baby’s brain and nervous system are developing, so you probably don’t have to worry.

This particular one where your baby’s head is turned to the same side as their arm is straight with their other arm bent at the elbow is called a tonic neck reflex. To help new parents be better informed, we have a comprehensive guide here with everything you need to know about this automatic response in babies.

What is the tonic neck reflex?

Image source: iStock

The tonic neck reflex, or “fencing” posture, actually begins in the womb 18 weeks after conception. In fact, this early reflex is believed to help your baby work its way through the birth canal. Additionally, the tonic neck reflex can also help your newborn discover their hands and develop their hand-eye coordination.

According to Healthline, this can last until your baby is around 5 to 7 months old.

If your newborn is on her back, her head will turn to one side while her arm and often her leg on the same side will extend. The opposite arm will then bend at the elbow and vice versa. It’s also called the fencing reflex because your baby’s posture makes it look like he’s ready to grab a sword and say, “On guard!”

The movement can even help your newborn discover their hands and develop early hand-eye coordination.

Tonic neck reflex test

tonic neck reflex

Image source: iStock

With a pediatrician

When examining your baby with the pediatrician, he may test the tonic neck reflex as well as other hard-wired newborn responses.

While your newborn is lying down, the pediatrician will gently turn her head to one side. They will then check if one arm will extend while the opposite arm bends. Your baby’s head will be turned to the other side to see if the same movement occurs.

At home

You can also observe the tonic neck reflex at home. Just lay your baby on their back and gently turn their head to the left. Then, when the reflex occurs, your baby will extend their left arm while flexing the right next to their head.

You can then gently turn your baby’s head to the right. Their right arm will extend and their left will bend.

If your baby doesn’t always react with this reflex, you don’t have to worry right away because every child is different and it may depend on how relaxed they are.

When should you worry?

tonic neck reflex

Image source: iStock

It is important to continue to observe your newborn’s reflexes. Your pediatrician checks this to know the development of your child’s brain and nervous system. Here are some things to watch out for when to call a doctor:

  • If your baby’s fencing posture also occurs.
    When your baby turns her head to the left, her left arm should be straight and her right arm slightly bent. then when they face right, their right arm is the one that extends and their left arm is bent. You should contact a doctor if either side looks different.
  • It’s time to call your pediatrician if your baby is moving better on one side of his body than the other.
  • There could be a problem with your baby’s nervous system if the tonic neck reflex goes away for a while and then comes back.
  • You should also tell your doctor if the reflex disappeared before about 4 to 5 months or if it persists beyond 7 months and into infancy.

Reflexes are one of the things that let us know that our babies are developing naturally. But if you notice anything unusual about your newborn’s movements, don’t hesitate to consult your child’s doctor about it.


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