Here's How to Decode Your Baby's Reflexes

Here's How to Decode Your Baby's Reflexes

Here’s the breakdown on baby’s baffling—but totally normal—built-in behaviors.

Almost everything about a newborn is overwhelming. On little-to-no sleep, you’re expected to assemble gear that requires an engineering degree. You can’t go out without carrying what feels like the entire contents of your home. Then you start to notice your baby is doing these...weird things. And your new-parent panic kicks in: What. Is. Happening!? No need to worry. Those fascinating, quirky little behaviors are natural, and actually serve a purpose. Here’s a guide to what means what, and when you should get your baby to the pediatrician.

 

What are baby reflexes?

Reflexes are involuntary, spontaneous movements that are part of normal infant development. Adults have them too; the “knee-jerk” reaction to a tap of your doctor’s hammer is probably the most familiar.

Infant developmental reflexes are also known as primitive reflexes, and they arise from the brain stem and spinal cord. “They are generally believed to exist because they have offered a survival benefit to human infants from an evolutionary perspective,” says Lauren Levine, M.D., assistant professor of Pediatrics at Columbia University Medical Center in Manhattan. Primitive newborn reflexes will generally fade away between 1 and 6 months of age.

“If you think that your infant’s reflexes persist past this age, you should let your pediatrician know,” Dr. Levine says. “But I tell parents not to stress about newborn reflexes. A good pediatrician will be assessing them at each well-baby visit without you even realizing it!”

 

The Rooting Reflex

What this is: When either side of a baby’s mouth is touched, he’ll turn his head in that direction, open his mouth, and root around. 

Why your baby roots: This helps a baby find the nipple and be able to feed. “You can imagine how an infant without these primitive reflexes might not have survived after birth thousands of years ago,” Dr. Levine notes.

In the first month of your baby’s life, when she’s learning how to eat and you’re learning how to feed her, you can leverage this reflex. “Stroking the baby’s face at the corner of the mouth can help encourage the baby to latch on or take the nipple in the mouth,” says Victoria Riese, M.D., of Flatiron Pediatrics in Manhattan. “Just be aware that a baby will root any time the cheek or corner of the mouth is stroked, so don’t mistake the reflex for a sign of hunger, especially if the baby has just eaten.”

 

The Sucking Reflex

What this is: When the roof of a baby’s mouth is touched, she immediately starts sucking. (Newborns also have a strong urge to put their fists in their mouths and suck on their own fingers.)

Why sucking pacifiers is important: Newborns’ neurological systems are immature in the first six months of life. “There needs to be a fail-safe method for the baby to get nourishment without any purposeful behavior, and then growth and development can follow,” Dr. Riese says. (This particular reflex isn’t completely cemented in utero until about 36 weeks, which is why preemies often have a compromised ability to feed.)

Sucking in general is soothing to babies, a secondary function of this reflex that probably developed to motivate babies to suck to get milk. “When a baby is fussy, putting a clean finger or pacifier in her mouth is extremely soothing and will help calm her very easily, especially if she has recently eaten and is not hungry,” Dr. Riese says. “This is one of the most useful methods to calm babies.”

 

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The Moro ("Startle") Reflex

What this is: In reaction to a sound or nearby sudden movement, a newborn throws back his head, extends his arms and legs out, then pulls his legs and arms back in. He might cry as well. Some babies even display this reflex in response to their own cry. “They are often the reason babies wake themselves up from sleep,” Dr. Levine says. “This is why swaddling infants helps them to sleep better. Their arms are tucked in and can’t flail about.”

Why baby needs to stay balanced: “The reflex movement adjusts the baby’s posture to keep him or her balanced. Once a baby develops more voluntary control over movements, these automatic responses fade away,” says Devorah Segal, M.D., Ph.D., pediatric neurologist at New York-Presbyterian Komansky Children’s Hospital and Weill Cornell Medicine in Manhattan. And a good sense of balance is quite useful for a new human to have. For one thing, it can make it easier to grab onto your mother if she should start to lose her grip on you.

 

The Tonic Neck ("Fencing Position") Reflex

What this is: When your baby is lying down, and his head is turned to one side, the arm on that same side extends out, while the other arm bends at his elbow, like a fencer would stand. 

How this protects baby: Much like the Moro reflex, Dr. Segal explains, this one likely originated as an automatic protective response to help maintain balance. After six months or so, “more purposeful balancing motions replace it,” she says.

 

The Palmar Grasp ("Grip") Reflex

What this is: Stroking your baby’s palm spurs her to close her fingers in a grasp. (A similar lesser-known reflex in the feet and toes usually lasts until babies are about 9 months old.)

Why this happens: It’s practice, essentially, for being able to master voluntary grasping, which will happen in a few months. Some experts call it a vestigial reflex, meaning its evolutionary purpose is no longer useful. It is thought to have originated as a way for babies to hang onto their mothers’ fur when humans were hairier. That alleviated the need for a mother to hold onto her baby while trying to, say, run from a predator.

 

The Stepping Reflex

What this is: Despite not being able to support his own weight, your baby moves his legs as though walking, even dancing, when you’re holding him upright with his feet touching a solid surface.

Why it's happening: This reflex is pretty much what it looks like: preparation and training for the all-important ability of humans to walk upright. 

“The best thing for parents to do when it comes to their infant’s primitive reflexes is to know what they are,” Dr. Levine notes. “That way, they’re not alarmed when they see them, and they’re able to tell the pediatrician if any of them are asymmetrical.” For example, your baby only grasps with her right hand and not the left, or, when startled, flails her left arm but not her right. “Such asymmetries could indicate a nerve or musculoskeletal injury from the birth process and need further evaluation,” Dr. Levine says. But remember, the reflexes themselves are not harmful to your baby in any way. Dr. Segal agrees: “There is nothing parents need to do to ‘train’ their baby out of a reflex. They will go away on their own over time.”