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In your first moments with your newborn, you likely already saw their reflexes.

The ones you might’ve noticed right away were the reflexes that help your baby eat, such as the rooting reflex or the sucking reflex. And, of course, your heart melted when their tiny fingers used the grasp reflex to wrap around your thumb for the first time.

These primitive reflexes are involuntary movements controlled by your baby’s brain stem for survival and proper development.

The symmetric tonic neck reflex (STNR), sometimes also called the symmetrical tonic neck reflex, is another very important reflex. You’ll start to see it when your baby is 6 to 9 months old.

The STNR helps your baby get onto their hands and knees, so it’s sometimes referred to as the crawling reflex.

Most definitions of STNR deal with the flexion (bending) and extension (stretching out) of baby’s upper and lower extremities — their arms and legs. Here’s a simple way to understand it:

  • When your baby’s head moves forward (their chin toward their chest), their legs straighten and their arms bend.
  • When your baby’s head moves backward (away from their chest), their legs bend and their arms straighten.

The reflex helps your baby learn to use the top half and the bottom half of their body independently of each other. This is significant for:

STNR integration

Like the rest of your little one’s primitive reflexes, the STNR is integrated — meaning, it disappears — as baby reaches 9 to 12 months old.

This is just about the time your baby’s ready to take those memorable first steps without holding on to anything for support.

As the STNR appears, your baby’s ATNR (asymmetric tonic neck reflex) goes away. You’ll see ATNR when your little one is lying on their back, with their:

  • face turned to one side
  • arm and leg extended on the side where their face is turned
  • arm and leg flexed on the opposite side

In this position, your baby resembles the classic pose of a fencer when they say “En garde!” That’s why ATNR is often referred to as the fencing reflex.

If your baby still has some of their STNR after 12 months, you may see them doing these things until it goes away:

  • “bear walking” on their hands and feet instead of crawling on their hands and knees
  • scooting while sitting
  • skipping the crawling stage and going directly to walking
  • preferring to lie on the floor instead of sitting

If your little one does these things — don’t worry. They can be perfectly normal stages to go through as a baby moves from sitting to walking, and your baby’s STNR might just disappear a little later.

According to a 2016 study done on 4 to 6 year olds, if primitive reflexes are retained too long, they may impact natural development and could indicate future social and educational difficulties.

The study authors suggested that primitive reflexes should be routinely tested. Chat about this with your pediatrician.

If you have concerns about your baby’s development, talk with your pediatrician. If the doctor suspects a delay or problem in your baby’s motor development, they may check for retained primitive reflexes such as STNR.

Your pediatrician will make sure your little one is exhibiting these reflexes properly and that they’re showing up and disappearing at expected ages.