When it comes to newborns, their tiny bodies can produce some fascinating—and often perplexing—movements. That adorable grin? It might just be gas. The way they clutch your finger can feel like a profound bond, but it’s likely just a reflex. So, if you catch your baby lying on their back, striking a pose reminiscent of a fencer about to duel, you might be tempted to think they’re destined for a career in swordplay (imagine those college scholarships!). Unfortunately, that’s just another reflex at play: the tonic neck reflex, which comes in two forms: asymmetrical and symmetrical. Here’s what you need to know about both.
What is Asymmetrical Tonic Neck Reflex (ATNR)?
Most discussions about tonic neck reflexes revolve around the asymmetrical tonic neck reflex (ATNR), often referred to as the “fencing position.” This reflex occurs when a baby turns their head to one side, extending the arm on that side while bending the opposite arm at the elbow. Typically, ATNR lasts until the baby is about five to seven months old. So, if your little one showcases ATNR around Halloween, you might just have the makings of a charming Robin Hood costume.
Why Does Tonic Neck Reflex Occur?
One theory suggests that this reflex aids the baby in navigating the birth canal during delivery. Once they’re in the world, ATNR can help babies discover their hands and improve their hand-eye coordination. To see this reflex, lay your baby on their back and gently turn their head to one side. If they have ATNR, the arm on the side they’re facing will stretch out, while the other arm will bend at the elbow.
What is Symmetrical Tonic Neck Reflex (STNR)?
In contrast to ATNR, the symmetrical tonic neck reflex (STNR) usually emerges between six and nine months of age and helps babies transition to a hands-and-knees position—hence its nickname, the “crawling reflex.” STNR involves a baby bending and stretching their arms and legs in a specific way:
- When a baby tucks their chin toward their chest, their legs straighten while their arms bend.
- Conversely, when a baby moves away from their chest, their legs bend and arms straighten.
This reflex is not only delightful to observe, but it also marks a crucial developmental step, enabling babies to coordinate their upper and lower body movements. However, STNR fades away between nine and twelve months as they start to walk.
In some cases, a child might continue to exhibit STNR even after their first birthday and once they’re walking well. If this happens, don’t worry; every child develops at their own pace. You might notice behaviors like:
- Walking on their hands and feet (like a bear)
- Scooting while seated
- Skipping a traditional crawling phase and going straight to walking
- Preferring to lounge on the floor rather than sit up
If you have concerns about your baby’s development, it’s best to consult with your pediatrician rather than anxiously second-guessing yourself. Most likely, everything is just fine. If there are issues, your doctor can guide you through what comes next.
Other Newborn Reflexes to Know
Several other reflexes can shed light on your baby’s movements and behaviors:
- Moro Reflex: Causes the baby to cry, throw back their head, and pull their limbs in.
- Rooting Reflex: This instinctive response occurs when the corner of a baby’s mouth is stroked, prompting them to “root” for a nipple.
- Grasp Reflex: Triggered by a light touch on the baby’s palm, leading them to grasp.
- Suck Reflex: Prepares the baby for nursing, starting around the 32nd week of pregnancy.
- Stepping Reflex: Also known as the walking or “dancing” reflex, it makes a baby appear to take steps when held upright with their feet touching a solid surface.
For further insights, check out this post on our blog, and for authoritative information, visit Make A Mom and RMANY.
Summary
The tonic neck reflex, both asymmetrical and symmetrical, is a fascinating aspect of infant development. Understanding these reflexes can help parents appreciate the remarkable growth and changes their babies undergo in the first year. If you have any concerns, always consult your pediatrician to ensure your baby’s health and development are on track.
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