My Baby Still Has the Fencing Reflex (Persistent ATNR)
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.
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By Age
What to expect by age
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.
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.
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.
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 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.
Sources
Related Resources
Trust your instincts. If something feels wrong, reach out to your pediatrician.
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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.
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.
My Baby Only Army Crawls
Army crawling (also called commando crawling) is a completely valid and normal way for babies to move. Many babies army crawl for weeks or even months before transitioning to hands-and-knees crawling, and some skip hands-and-knees crawling entirely. What matters is that your baby is independently mobile and exploring their environment.
One Side of My Baby's Body Moves Differently
Babies should generally use both sides of their body equally. If one side consistently moves differently, is weaker, stiffer, or less coordinated, this warrants evaluation. Asymmetric movement can indicate hemiplegia (cerebral palsy affecting one side), brachial plexus injury, or other neurological conditions that benefit from early therapy.