Primitive Reflexes: What Parents Should Know

Babies are born with primitive reflexes that help them move and develop, and each one should fade as baby grows. Here's a guide to the main ones, and what to do if one hangs around too long.

The newborn reflexes at a glance

Babies are born with a whole set of primitive reflexes: palmar, plantar, rooting, Landau, ATNR, STNR, TLR, Moro, and stepping. Each one is present at a certain time and tells us something about your baby's nervous system.

The rooting reflex can even help your baby turn their head.

The ATNR, or fencing reflex

The ATNR (asymmetrical tonic neck reflex) is initiated by head rotation. It's known as the 'fencing reflex' and is present at birth. When a baby turns their head, the arm on the side of the neck rotation extends while the arm on the opposite side bends at the elbow. Normally this reflex starts to go away around the time a baby learns to roll, at about 4 to 6 months, and learning to roll and crawl on hands and knees helps it go away.

You can spot a retained ATNR in a few ways. If you notice a bend in the elbow on the opposite arm from the way your baby is turning their neck, the reflex is still present. When your child crawls and looks to the side, the opposite elbow may bend or collapse. A stiff arm or stiff leg on one side of the body, a rotational preference where your baby is always looking the same direction, or eyes shifting away from midline can also point to it, since the reflex hangs around when a baby has a preferred neck rotation.

If the ATNR doesn't integrate, it can impact bilateral coordination, balance, crossing midline, attention, knowing the difference between right and left sides of the body, visual tracking, binocular vision, depth perception, bilateral hand play, gross motor milestone achievement, and later academics such as reading and writing. To help it integrate, work on dissociating the head from the body once your child is up on extended arms by having them look left and right. You can also use the ATNR to help dress your baby.

The STNR

The STNR (symmetrical tonic neck reflex) is precipitated by head movement into flexion (down) or extension (up) when a baby is on hands and knees. Looking down causes the arms to collapse and the legs to straighten, while looking up causes the arms to straighten and the legs to flex. It should disappear by 9 to 10 months.

This reflex gets integrated through crawling on hands and knees. If retained, it can impact emotional regulation, hand-eye coordination, spatial awareness, and attention. Work on looking up and down when on hands and knees to help it integrate.

Head and trunk righting reactions

Head and trunk righting is how we check whether your baby can find their way back to midline when they 'fall' to the side. Through their balance and vision systems, they should lift their head and trunk up evenly on both sides.

This matters because with torticollis, one side often gets tighter and shorter while the other side gets weaker and longer. Gaining full neck range of motion is only step one. Step two is making sure your baby's muscles are strong and balanced on both sides so they can use that motion in everyday play and milestones. That balance helps your baby hit sitting, crawling, and walking milestones symmetrically and with ease.