Neonatal Reflexes

Encyclopedia of Childhood and Adolescence, Apr 06, 2001

Neonatal reflexes are the reflexes that are present at birth. They are believed to be inborn and have predictable action patterns. Reflexes, more accurately described as unconditioned reflexes, are not learned or developed through experience. Normally developing neonates (infants up to about four weeks of age) are expected to respond to specific stimuli with a specific, predictable behavior or action. Any variation in, or absence of, response may be a sign of abnormality in development. Further testing of the infant is usually recommended when any response to a stimulus differs from the expected norm. Some neonatal reflexes disappear with maturation; other persist into adulthood.

Although reflex actions are complex, most reflexes can be simplified into four basic steps. In the first step, the stimulus is received by nerve endings involving one of the senses--taste, sight, smell, hearing, or touch. Secondly, the energy created by the stimulus is conducted through the nerves to the central nervous system. Next, the impulses generated by the stimulus are transmitted to the nerves that stimulate muscle action. Finally, the muscles, and sometimes certain glands, respond with an action.

The Babinski reflex is characterized by a fanning of all five toes and the stretching forward of the big toe when the bottom of the foot is stroked or tickled. It is a sign that the infant is neurologically normal. Usually around the age of one this reflex disappears completely. It is replaced with the plantar reflex found in young children and adults; this reflex involves curling of the toes in response to the stroking of the sole of the foot.

The blink reflex is characterized by the involuntary blink of the eyes when an infant is subjected to a bright light, wind, or rapid approach of an object. This involuntary action protects the eyes and is therefore maintained throughout life.

When a newborn infant is placed on her stomach, she may begin to flex her arms and legs in a motion that simulates crawling. This action is due to the baby's natural curled-up position, which gradually changes over the days following birth. After about one week, the infant will be able to lie flat, and the false crawling movements will disappear.

The knee-jerk, or patellar reflex, is a sign of a neurologically healthy baby; the neonate's lower leg and foot involutarily kick upward or forward when the neonate is tapped on the tendon just below the patella (kneecap). This reflex prevails throughout maturation into adult life. It is checked by applying the stimulus tap to a young child or adult while he or she is in a sitting position. This reflex is so commonly known that the term "knee-jerk" response is an idiom for any reaction that seems to come automatically, with little or no thought.

At about three months of age, an infant will begin to display the Landau's reflex. When she is placed on her stomach face down, she will raise her head and arch her back. This reflex will persist until around the child's first birthday. Absence of this reflex suggests problems in motor development. The pediatrician may investigate further to rule out such problems as cerebral palsy and mental retardation .

Also referred to as Moro's reflex, the startle reaction, or the embracing reflex, the Moro reflex is characterized by a "grabbing" motion if an infant is subjected to a loud noise or loss of support. The infant's arms and legs will extend and then come together. The infant's back will also arch, and the infant may cry. This reflex, like other neonatal reflexes, is the sign of a neurologically normal newborn infant. Between the ages of five and seven the child will lose this reflex; if the reflex persists, it is a sign of brain damage, neurological impairment, or motor reflex difficulties.

The stimulus for this reflex, which turns the neonate's head to one side, is applied when the neonate is lying on his or her back facing upward. The neonate's reflex response is to turn his or her shoulders and body in the same direction as the head. This reflex disappears after a few weeks; if it persists after infancy, it may indicate abnormal development of the central nervous system.

The palmar grasp reflex is characterized by the grasping of an object that is placed crosswise on the palm of a newborn infant, or neonate. Like the other neonatal reflexes, it is a sign of normal neurological development. Immediately following birth, the hand grip of this reflex is strong enough to support the baby's weight. Within a few hours, this strength will begin to wane, and the reflex usually fades completely after three to four months.

The rage reflex is the newborn infant's reponse to having his or her movements suddenly restrained. The infant responds by strongly resisting the restraint, developing redness in the face, or crying. Like the other neonatal reflexes, the rage reflex is a sign of normal neurological development. This reflex tends to diminish in intensity before six months of age.

When a newborn infant's cheek is touched or stroked, she will respond automatically by turning her head toward that side and beginning to suck. This is the reflex that allows the newborn to turn toward the mother's nipple to begin breastfeeding . Usually during the first six months of life, but sometimes as late as 12 months of age, this reflex disappears. The rooting reflex is the sign of a neurologically normal neonate.