Biological Survival Mechanisms: A reflex is a biological survival mechanism. Each infant possesses a set of "built-in" reflexes to help him or her survive during those first vulnerable months of life. For example, the rooting reflex helps an infant locate the breast or bottle for feeding, while the sucking reflex allows an infant to ingest breast milk or formula immediately at birth. Therefore, these are hardwired neural pathways that provide an infant with the ability to interact with the environment before developing consciousness. Transition to Voluntary Control: As the infant's brain develops, the higher brain centers are involved in the gradual loss of these primitive reflexes. For example, at approximately six months of age, an infant no longer demonstrates the "palmar grasp" reflex; rather, the infant has developed the voluntary ability to reach out and grasp objects. The persistence of the palmar grasp reflex after seven or eight months may delay an infant's ability to develop fine motor skills. Medical Diagnostic Tools: There are several methods by which I assess an infant's neurological development. One tool I use is the "tonic neck" reflex (observed when an infant assumes the "fencing" position), and another is the Babinski reflex, where the big toe extends and other toes fan out when the foot is stroked. The presence of the Babinski reflex up to approximately two years of age is considered normal; however, its presence in children greater than two years of age indicates they have an underlying neurological disorder. Safe Home Observation: To evaluate the presence of the Moro or startle reflex safely at home, a caregiver can observe the child during a diaper change. An infant's startle reflex may be elicited by sudden movement or loud sounds. The infant will extend his/her arms and legs, cry briefly, and pull his/her limbs back into the body. The "hugging" motion confirms that the infant's vestibular system is functioning appropriately and communicating with the brain.
Defining Primitive Reflexes: Newborns develop within the womb and are born with specific sensory stimuli, acting as the primary survival mechanism. These "primitive" responses are governed by the brain stem and spinal cord to ensure survival before the higher brain centers—the cortex—take over to control voluntary movement. The Integration Timeline: Most newborns will naturally integrate these reflexes between the ages of two and six months. For example, the stepping reflex usually disappears by two months, while the rooting and Moro reflexes typically subside by four months. If a primitive reflex does not disappear within its expected window, it can serve as a clinical "red flag" for potential neurological developmental delays or issues with the maturation of the brain's voluntary motor pathways. Clinical Testing Procedures: During assessments, physicians perform systematic physical maneuvers to elicit these responses to see if the reflex occurs equally on both sides of the body. Any asymmetries noted during assessment may indicate a localized injury, such as a fractured clavicle or a nerve injury like brachial plexus palsy. Checking the Moro Reflex at Home: Parents can check the Moro reflex (also referred to as the "startle reflex") at home by simulating a sudden position change while being safe. First, take your child in your arms while you are both awake, and support their head and neck while holding them. Then, you will quickly and gently drop both of your arms straight down approximately 1-2 inches (and stop). This sudden sensation of "falling" should cause the baby to throw out the arms with the palms up and quickly retract the arms toward the body. While loud noises can also elicit the Moro reflex, the actual "drop" method is usually the only reliable one in a clinical setting to attain an accurate response.
Newborn reflexes or primitive reflexes, such as Moro Reflex, Palmar Grasp Reflex, Plantar Grasp Reflex, Sucking Reflex, Babinski Reflex, and some more, are automatic motor responses to specific stimuli that are present from birth and are controlled by subcortical brain structures and the spinal cord, persisting through early infancy. These reflexes present the earliest, simplest, and most frequently used tools, giving a valuable clinical insight to clinicians to assess the neurological function and integrity in newborns and young children. These reflexes follow predictable timelines of appearance and disappearance as the central nervous system matures and higher cortical centers develop voluntary motor control, making their disappearance or persistence clinically significant for clinicians since the disappearance of these reflexes represents the normal inhibition of subcortical responses by developing cortical structures. The timeline of their disaperance dependson each reflex, but generally Most such as the Moro, rooting, palmar grasp, Galant, and asymmetric tonic neck reflex, disappear by about 4 to 6 months of age, while the stepping reflex typically fades earlier, around 2 to 3 months. Is there a test my doctor might conduct to check these reflexes? Yes, Pediatricians and child neurologists routinely assess primitive reflexes during well-child visits and neurological examinations as part of developmental surveillance, and each reflex has its Specific Testing Method. Moro reflex is a response to sudden loss of support or loud noise, characterized by arm extension-abduction with finger spreading, followed by arm flexion-adduction, often accompanied by crying. I have to stress that deliberately eliciting the Moro reflex unnecessarily should be avoided, as it activates the infant's fear system and can cause distress to your baby. To gently check the Moro reflex at home, place your baby on a firm, safe surface and support their head and shoulders. Lift the head slightly, then carefully lower it back a small amount (never drop or shake). A normal response is both arms extending outward with fingers open, then coming back in, often with brief crying. The movement should be symmetrical—if one arm responds differently, the reflex is absent, or it persists strongly beyond 6 months, consult your pediatrician. Thank you Dr. Seyed Hassan Fakher MD Preventive Health & Sports Medicine https://www.invigormedical.com/contributor/dr-seyed-hassan-fakher-md/