Medical Conditions

Persistent Fencing Reflex (ATNR) in Infants

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published AAP, NIH guidelines

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If your baby has been diagnosed with or you suspect persistent fencing reflex (atnr) in infants, here is what the evidence says.

The short answer

The asymmetric tonic neck reflex (ATNR), or fencing reflex, is a normal primitive reflex where turning the head causes the arm and leg on that side to extend while the opposite limbs flex. It is present from birth and should fade by 4-6 months. A persistent ATNR beyond 6 months may indicate a neurological concern and should be evaluated.

Key takeaways

  • The asymmetric tonic neck reflex (ATNR), or fencing reflex, is a normal primitive reflex where turning the head causes the arm and leg on that side to extend while the opposite limbs flex. It is present from birth and should fade by 4-6 months. A persistent ATNR beyond 6 months may indicate a neurological concern and should be evaluated.
  • Usually normal when: Fencing posture visible in the first 4-6 months when head is turned
  • Call your doctor if: An obligatory ATNR at any age where the baby cannot break free from the fencing position
  • Varies by age — see the age-by-age breakdown below
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What Parents Should Know

According to AAP, NIH guidelines, the asymmetric tonic neck reflex (ATNR), or fencing reflex, is a normal primitive reflex where turning the head causes the arm and leg on that side to extend while the opposite limbs flex. It is present from birth and should fade by 4-6 months. A persistent ATNR beyond 6 months may indicate a neurological concern and should be evaluated. At 0-1 month, the ATNR is a normal reflex present from birth. When your baby's head is turned to one side, the arm and leg on the face side extend while the opposite arm and leg flex, creating a "fencing" position. This reflex is thought to prepare for hand-eye coordination. It should not be obligatory, meaning your baby should still be able to move their limbs freely even when the head is turned. An obligatory ATNR (where the baby is stuck in the fencing position) at any age is a concern. It is generally considered normal when fencing posture visible in the first 4-6 months when head is turned. However, you should contact your pediatrician promptly if an obligatory ATNR at any age where the baby cannot break free from the fencing position.

Sources: [1], [2]

Normal vs. Concerning

Usually Normal
Worth Discussing
Fencing posture visible in the first 4-6 months when head is turned
An obligatory ATNR at any age where the baby cannot break free from the fencing position
Baby can still move limbs freely despite the reflex
Persistent ATNR beyond 6 months combined with other developmental delays or abnormal muscle tone
The reflex is not obligatory (baby is not stuck in the position)
The ATNR seems very strong or obligatory (baby gets stuck in the position)
The reflex gradually fades by 4-6 months
The reflex is still prominent at 5-6 months

By Age

What to expect by age

0-1 month

The ATNR is a normal reflex present from birth. When your baby's head is turned to one side, the arm and leg on the face side extend while the opposite arm and leg flex, creating a "fencing" position. This reflex is thought to prepare for hand-eye coordination. It should not be obligatory, meaning your baby should still be able to move their limbs freely even when the head is turned. An obligatory ATNR (where the baby is stuck in the fencing position) at any age is a concern.

1-3 months

The ATNR may be quite prominent during this period and is still considered normal. You may notice it when your baby turns their head during sleep or while lying on their back. As voluntary movement develops, the reflex becomes less dominant. Your baby should be able to bring their hands to midline (together in front of them) even with the reflex present.

3-6 months

The ATNR should begin to fade significantly by 4-6 months. As your baby gains voluntary motor control, the reflex becomes less noticeable. By 6 months, your baby should be able to bring hands to midline, reach with both hands, and not be dominated by the fencing posture when the head is turned.

6-12 months

The ATNR should not be present beyond 6 months. A persistent ATNR can interfere with rolling, reaching across midline, and hand-eye coordination development. If you notice that your baby still assumes the fencing position frequently when the head turns, discuss this with your pediatrician for neurological evaluation.

What to Tell Your Pediatrician

  • Describe when you first noticed persistent fencing reflex (atnr) in infants and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if the ATNR seems very strong or obligatory (baby gets stuck in the position).
  • Mention if the reflex is still prominent at 5-6 months.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Fencing posture visible in the first 4-6 months when head is turned
  • Baby can still move limbs freely despite the reflex
  • The reflex is not obligatory (baby is not stuck in the position)
  • The reflex gradually fades by 4-6 months
Mention at your next visit when...
  • The ATNR seems very strong or obligatory (baby gets stuck in the position)
  • The reflex is still prominent at 5-6 months
  • Your baby has difficulty bringing hands to midline or reaching across the body
Act now when...
  • An obligatory ATNR at any age where the baby cannot break free from the fencing position
  • Persistent ATNR beyond 6 months combined with other developmental delays or abnormal muscle tone

What You Can Do at Home

  • Keep track of when you notice persistent fencing reflex (atnr) in infants — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that fencing posture visible in the first 4-6 months when head is turned — this is generally within the range of normal.
  • At 0-1 month, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
  • While monitoring at home, seek immediate care if an obligatory ATNR at any age where the baby cannot break free from the fencing position.

Missing Primitive Reflexes in Newborns

Primitive reflexes (Moro, rooting, sucking, grasp, stepping) are expected in all healthy newborns and are tested as part of the newborn neurological exam. Absent or significantly diminished reflexes may indicate a neurological concern, prematurity-related immaturity, or the effects of medication and should be evaluated by your pediatrician.

Excessive Moro (Startle) Reflex in Newborns

The Moro (startle) reflex is a normal primitive reflex present in all newborns. Some babies seem to have a more active or sensitive startle reflex, which can cause them to wake frequently during sleep. This is a normal variation and typically diminishes by 3-4 months of age. Swaddling can help reduce the impact of the Moro reflex on sleep.

Early Hand Preference in Newborns (Using One Hand Only)

Babies should not show a strong hand preference before 12-18 months of age. If your newborn or young infant consistently uses one hand much more than the other, or seems to ignore one hand, it could indicate a neurological concern or birth injury that should be evaluated by your pediatrician. True handedness normally develops between 2-4 years of age.

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When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is persistent fencing reflex (atnr) in infants normal?
The asymmetric tonic neck reflex (ATNR), or fencing reflex, is a normal primitive reflex where turning the head causes the arm and leg on that side to extend while the opposite limbs flex. It is present from birth and should fade by 4-6 months. A persistent ATNR beyond 6 months may indicate a neurological concern and should be evaluated.
When should I call the doctor about persistent fencing reflex (atnr) in infants?
An obligatory ATNR at any age where the baby cannot break free from the fencing position Persistent ATNR beyond 6 months combined with other developmental delays or abnormal muscle tone
When is persistent fencing reflex (atnr) in infants normal?
Fencing posture visible in the first 4-6 months when head is turned Baby can still move limbs freely despite the reflex The reflex is not obligatory (baby is not stuck in the position)
What causes persistent fencing reflex (atnr) in infants?
The asymmetric tonic neck reflex (ATNR), or fencing reflex, is a normal primitive reflex where turning the head causes the arm and leg on that side to extend while the opposite limbs flex. It is present from birth and should fade by 4-6 months. A persistent ATNR beyond 6 months may indicate a neurological concern and should be evaluated. Common explanations include: Fencing posture visible in the first 4-6 months when head is turned. Baby can still move limbs freely despite the reflex.
What should I mention to my pediatrician about persistent fencing reflex (atnr) in infants?
You should mention persistent fencing reflex (atnr) in infants at your next visit if: The ATNR seems very strong or obligatory (baby gets stuck in the position). The reflex is still prominent at 5-6 months. Your baby has difficulty bringing hands to midline or reaching across the body.
Is persistent fencing reflex (atnr) in infants normal at 0-1 month?
The ATNR is a normal reflex present from birth. When your baby's head is turned to one side, the arm and leg on the face side extend while the opposite arm and leg flex, creating a "fencing" position. This reflex is thought to prepare for hand-eye coordination. It should not be obligatory, meaning your baby should still be able to move their limbs freely even when the head is turned. An obligatory ATNR (where the baby is stuck in the fencing position) at any age is a concern.
Is persistent fencing reflex (atnr) in infants normal at 1-3 months?
The ATNR may be quite prominent during this period and is still considered normal. You may notice it when your baby turns their head during sleep or while lying on their back. As voluntary movement develops, the reflex becomes less dominant. Your baby should be able to bring their hands to midline (together in front of them) even with the reflex present.
Should I go to the ER for persistent fencing reflex (atnr) in infants?
Seek emergency care if an obligatory ATNR at any age where the baby cannot break free from the fencing position, or if persistent ATNR beyond 6 months combined with other developmental delays or abnormal muscle tone. When in doubt, call your pediatrician's after-hours line for guidance.
Does persistent fencing reflex (atnr) in infants go away on its own?
In many cases, persistent fencing reflex (atnr) in infants resolves on its own, especially when fencing posture visible in the first 4-6 months when head is turned. By 6-12 months, the ATNR should not be present beyond 6 months. A persistent ATNR can interfere with rolling, reaching across midline, and hand-eye coordination development. If you notice that your baby still assumes the fencing position frequently when the head turns, discuss this with your pediatrician for neurological evaluation.
AAPNIH

References

  1. [1]American Academy of Pediatrics. Newborn Reflexes. HealthyChildren.org. AAP
  2. [2]National Library of Medicine. Primitive Reflexes. StatPearls. NIH

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Persistent Fencing Reflex (ATNR) in Infants.

Things to mention

  • Describe when you first noticed persistent fencing reflex (atnr) in infants and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if the ATNR seems very strong or obligatory (baby gets stuck in the position).
  • Mention if the reflex is still prominent at 5-6 months.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • The ATNR seems very strong or obligatory (baby gets stuck in the position)
  • The reflex is still prominent at 5-6 months
  • Your baby has difficulty bringing hands to midline or reaching across the body

Urgent signs to report immediately

  • An obligatory ATNR at any age where the baby cannot break free from the fencing position
  • Persistent ATNR beyond 6 months combined with other developmental delays or abnormal muscle tone

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

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Related Resources

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Bottom line

Most cases of persistent fencing reflex (atnr) in infants are normal. Talk to your pediatrician if an obligatory atnr at any age where the baby cannot break free from the fencing position.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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Missing Primitive Reflexes in Newborns

Primitive reflexes (Moro, rooting, sucking, grasp, stepping) are expected in all healthy newborns and are tested as part of the newborn neurological exam. Absent or significantly diminished reflexes may indicate a neurological concern, prematurity-related immaturity, or the effects of medication and should be evaluated by your pediatrician.

Excessive Moro (Startle) Reflex in Newborns

The Moro (startle) reflex is a normal primitive reflex present in all newborns. Some babies seem to have a more active or sensitive startle reflex, which can cause them to wake frequently during sleep. This is a normal variation and typically diminishes by 3-4 months of age. Swaddling can help reduce the impact of the Moro reflex on sleep.

Early Hand Preference in Newborns (Using One Hand Only)

Babies should not show a strong hand preference before 12-18 months of age. If your newborn or young infant consistently uses one hand much more than the other, or seems to ignore one hand, it could indicate a neurological concern or birth injury that should be evaluated by your pediatrician. True handedness normally develops between 2-4 years of age.

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