When your newborn is lying on their back, do you notice they often look like they have assumed the position of a fencer ready for swordplay? With their head turned to the same side as their outstretched arm and their other arm bent at the elbow, it may look like they are about to exclaim, “En garde!”
Some parents think this position also resembles a cute, little archer, as if the extended arm is holding a bow and the bent arm is pulling back the bowstring loaded with an arrow.
In fact, this is the tonic neck reflex. Here’s what you need to know.
The tonic neck reflex begins about 18 weeks after conception. That’s right — the associated movements start in the womb. It’s one of the most easily recognized primitive reflexes, and it lasts until your baby is around 5 to 7 months old.
It is thought that, during birth, tonic neck reflex helps your baby make their way down the birth canal. And following birth, tonic neck reflex may help your newborn to discover their hands and develop hand-eye coordination.
The tonic neck reflex is often called the fencing reflex. When your baby is lying down and their head is turned to the right or left, the corresponding arm extends while the other arm bends next to their head. This makes them look like they’re about to start fencing.
Terminology
The tonic neck reflex (TNR) is also called the asymmetric(al) tonic neck reflex (ATNR). There’s also a symmetric(al) tonic neck reflex (STNR), which comes later in infancy and is less talked about.
When doctors talk about the TNR, they’re usually referencing the ATNR, not the STNR.
To look for the tonic neck reflex, put your baby on their back and gently turn their head so their face is looking left. When this reflex happens, the left arm will reach out straight and the right arm will flex next to the head.
Gently turn your baby’s head so their face is looking right, and the right arm will extend and the left arm will flex.
Don’t worry if you don’t always see your baby react with this reflex. It can depend on how relaxed they are or whether they’re distracted by something else going on in the room.
A reflex is an automatic reaction to stimulation. There is no thought, just an involuntary reaction.
Your baby comes equipped with primitive reflexes, often referred to as newborn reflexes or infant reflexes. Their primary function is self-preservation and to help with movement and development.
Your baby’s primitive reflexes can serve as an important sign of nervous system function and development. Your pediatrician can use your baby’s primitive reflexes to help observe their central nervous system function.
Many of your baby’s reflexes will disappear as they grow older, such as the tonic neck reflex that typically disappears when your baby reaches 5 to 7 months.
As a child ages, if primitive reflexes remain or reappear after they are expected to disappear, it may be an indication of brain or nervous system problems. But this certainly isn’t always the case. Talk to your pediatrician if you have any developmental concerns.
Some primitive reflexes remain through adulthood, such as:
- Blink reflex: Your eyes reflexively blink in reaction to a sudden bright light or being touched.
- Sneeze reflex: You sneeze in reaction to your nasal passages being irritated.
- Gag reflex: You gag in reaction to the back of your mouth or throat being stimulated.
Along with tonic neck reflex, you may notice many of your baby’s other reflexes, such as:
- Grasp reflex: Stroke your baby’s palm, and they’ll grasp your finger (and melt your heart).
- Parachute reflex: Quickly (but gently) rotate your upright baby to face forward and down to simulate falling, and they’ll extend their arms.
- Rooting reflex: Stroke your newborn’s cheek, and they’ll open their mouth and turn their head toward the stroke.
- Startle (Moro) reflex: Tilt your baby with a movement backward (support their head!), and they’ll throw back their head and extend their arms and legs. Unexpected, loud sounds may provoke this reflex, too.
- Stepping reflex: Hold your baby upright and place their feet on a flat surface, and they’ll appear to take steps and walk.
- Suck reflex: Touch the roof of your baby’s mouth, and they’ll begin to suck.
Your baby naturally has primitive reflexes that go away as coordinated, voluntary movements appear. One of the most noticeable is the tonic neck reflex, which typically disappears by 5 to 7 months of age.
The absence of certain primitive reflexes in the newborn stage — or their persistence beyond babyhood — can be a sign of a neurological problem, but that isn’t always the case. Check with your pediatrician, as always, if you have questions about your little one’s development.