My Baby Still Has the Fencing Reflex (Persistent ATNR)
Medically reviewed by Dr. Sarah Chen, MD, FAAP · Board-Certified Pediatrician
Content reviewed against published AAP, NIH, CDC guidelines
Last reviewed:
Your baby's physical development is unique, and concerns about still has the fencing reflex (persistent atnr), here is what you need to know.
The short answer
The asymmetric tonic neck reflex (ATNR, also called the fencing reflex) causes your baby to extend the arm on the side they are looking toward. It should integrate between 4-6 months. If the ATNR persists strongly beyond 6 months, it can interfere with bringing hands to midline, bilateral hand use, and rolling. Evaluation is recommended.
Key takeaways
- The asymmetric tonic neck reflex (ATNR, also called the fencing reflex) causes your baby to extend the arm on the side they are looking toward. It should integrate between 4-6 months. If the ATNR persists strongly beyond 6 months, it can interfere with bringing hands to midline, bilateral hand use, and rolling. Evaluation is recommended.
- Usually normal when: Your baby is under 5 months and shows ATNR intermittently.
- Call your doctor if: ATNR is getting stronger.
- Varies by age — see the age-by-age breakdown below
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What Parents Should Know
According to AAP, NIH, CDC guidelines, the asymmetric tonic neck reflex (ATNR, also called the fencing reflex) causes your baby to extend the arm on the side they are looking toward. It should integrate between 4-6 months. If the ATNR persists strongly beyond 6 months, it can interfere with bringing hands to midline, bilateral hand use, and rolling. Evaluation is recommended. At 0-3 months, the ATNR is normal and should be present. When your baby turns their head, the arm on that side extends while the opposite arm flexes. This helps develop early hand-eye coordination. It should not be the dominant posture but should be elicited by head turning. It is generally considered normal when your baby is under 5 months and shows ATNR intermittently. However, you should contact your pediatrician promptly if aTNR is getting stronger.
Normal vs. Concerning
By Age
What to expect by age
0-3 months
The ATNR is normal and should be present. When your baby turns their head, the arm on that side extends while the opposite arm flexes. This helps develop early hand-eye coordination. It should not be the dominant posture but should be elicited by head turning.
3-5 months
The ATNR should be weakening. Your baby should be able to bring hands to midline and mouth their hands even when their head is turned. If the ATNR is still very strong and your baby is locked into the fencing posture, discuss it with your pediatrician.
5-7 months
The ATNR should be integrated by now. Your baby should freely bring hands to midline regardless of head position. Persistent ATNR at this age can delay bilateral hand use, rolling, and crawling.
7-12 months
A persistent ATNR at this age significantly warrants evaluation. It can be a sign of neurological differences and will interfere with many motor skills. Physical therapy can help with reflex integration.
What to Tell Your Pediatrician
- Describe when you first noticed still has the fencing reflex (persistent atnr) and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if aTNR is still obligatory (baby locked in position) beyond 4 months.
- Mention if aTNR prevents your baby from bringing hands to midline.
- 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
- Your baby is under 5 months and shows ATNR intermittently.
- Your baby can bring hands to midline despite some ATNR.
- The ATNR is gradually weakening.
- ATNR is still obligatory (baby locked in position) beyond 4 months.
- ATNR prevents your baby from bringing hands to midline.
- The reflex persists beyond 6 months.
- ATNR is getting stronger.
- Your baby has other persistent reflexes alongside ATNR.
What You Can Do at Home
- Keep track of when you notice still has the fencing reflex (persistent atnr) — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your baby is under 5 months and shows ATNR intermittently — this is generally within the range of normal.
- At 0-3 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Provide plenty of supervised floor time and tummy time to support your baby's physical development.
- While monitoring at home, seek immediate care if aTNR is getting stronger.
Related Conditions
My Baby's Primitive Reflexes Are Not Integrating
Primitive reflexes are automatic movements present at birth that should gradually integrate (disappear) during the first year as your baby develops voluntary movement control. If reflexes persist beyond their expected timeframe, it may indicate neurological immaturity or developmental concerns. Your pediatrician checks reflexes at well visits.
Baby Not Bringing Hands to Midline
Bringing hands to midline - the center of the body - is an important early motor milestone that typically develops between 3 and 4 months. Before this, babies tend to keep their hands to their sides or near their face. Once midline play develops, you will see your baby clasping their hands together, reaching for toys with both hands, and bringing objects to their mouth. This skill lays the foundation for many later abilities like transferring objects between hands and self-feeding.
My Baby Has Difficulty Using Both Hands Together
Bilateral coordination (using both hands together) develops gradually. Babies begin bringing hands to midline around 3-4 months and use both hands together for tasks like holding a bottle or banging objects by 7-9 months. If your baby consistently avoids using both hands together by 9-10 months, mention it to your pediatrician.
Related Resources
Milestone Checklists by Age
Track your baby's developmental milestones from birth to 5 years with age-specific checklists.
Month-by-Month Development
Detailed monthly development guides from birth through 24 months.
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 still has the fencing reflex (persistent atnr) normal?
When should I call the doctor about still has the fencing reflex (persistent atnr)?
When is still has the fencing reflex (persistent atnr) normal?
What causes still has the fencing reflex (persistent atnr)?
What should I mention to my pediatrician about still has the fencing reflex (persistent atnr)?
Is still has the fencing reflex (persistent atnr) normal at 0-3 months?
Is still has the fencing reflex (persistent atnr) normal at 3-5 months?
Should I go to the ER for still has the fencing reflex (persistent atnr)?
Does still has the fencing reflex (persistent atnr) go away on its own?
References
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss My Baby Still Has the Fencing Reflex (Persistent ATNR).
Things to mention
- Describe when you first noticed still has the fencing reflex (persistent atnr) and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if aTNR is still obligatory (baby locked in position) beyond 4 months.
- Mention if aTNR prevents your baby from bringing hands to midline.
- 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
- ATNR is still obligatory (baby locked in position) beyond 4 months.
- ATNR prevents your baby from bringing hands to midline.
- The reflex persists beyond 6 months.
Urgent signs to report immediately
- ATNR is getting stronger.
- Your baby has other persistent reflexes alongside ATNR.
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
Bottom line
Most cases of still has the fencing reflex (persistent atnr) are normal. Talk to your pediatrician if atnr is getting stronger.
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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Related Physical Concerns
My Baby's Primitive Reflexes Are Not Integrating
Primitive reflexes are automatic movements present at birth that should gradually integrate (disappear) during the first year as your baby develops voluntary movement control. If reflexes persist beyond their expected timeframe, it may indicate neurological immaturity or developmental concerns. Your pediatrician checks reflexes at well visits.
Baby Not Bringing Hands to Midline
Bringing hands to midline - the center of the body - is an important early motor milestone that typically develops between 3 and 4 months. Before this, babies tend to keep their hands to their sides or near their face. Once midline play develops, you will see your baby clasping their hands together, reaching for toys with both hands, and bringing objects to their mouth. This skill lays the foundation for many later abilities like transferring objects between hands and self-feeding.
My Baby Has Difficulty Using Both Hands Together
Bilateral coordination (using both hands together) develops gradually. Babies begin bringing hands to midline around 3-4 months and use both hands together for tasks like holding a bottle or banging objects by 7-9 months. If your baby consistently avoids using both hands together by 9-10 months, mention it to your pediatrician.
Should I Use Adjusted Age for My Preemie's Milestones?
Yes — for premature babies, developmental milestones should be assessed using adjusted (corrected) age, not chronological age, until at least 2 years of age. Adjusted age is calculated by subtracting the number of weeks your baby was born early from their actual age. For example, a 6-month-old born 2 months early would have an adjusted age of 4 months, and should be assessed against 4-month milestones. Most pediatricians use adjusted age for developmental assessment through age 2-3, and for growth charts through age 2.
Baby-Proofing a Small Apartment
Baby-proofing a small apartment is absolutely possible and focuses on the same key safety principles as any home: securing furniture to walls, covering outlets, locking cabinets with hazardous materials, and ensuring safe sleep spaces. Small spaces actually have an advantage - there is less area to monitor. Focus on eliminating the most dangerous hazards first: falls, poisoning, choking, and burns.
My Baby Seems to Use One Side More Than the Other
Babies should use both sides of their body fairly equally during the first 18 months of life. While slight preferences can be normal, a consistent pattern of favoring one side - using one arm much more than the other, crawling with one leg dragging, or turning the head predominantly one way - should always be discussed with your pediatrician. Early identification of asymmetry leads to the best outcomes.