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The grasp reflex is a phenomenon seen in newborn babies that indicates normal neurological development. Often referred to as the "palmar grasp reflex," it causes a baby’s hand to close into a grasping position to hold an object when the palm is touched. The primitive reflex can be tested at birth, and occurs until the baby is five to six months old when the frontal cortex of the brain is developed enough to inhibit it. It can be strong enough to support an infant’s total body weight and, although the reflex can let go at any time, it can be triggered to release by stroking the back of a baby’s hand.
An involuntary reflex, the grasp reflex is controlled by the central nervous system. It is a reflex used to test the neurological state of infants, in addition to other reflexes of the hips, neck, and arms. Reflex testing is performed during any physical evaluation of a baby and is an essential part of a sensory examination. If the grasp reflex is not present, or persists beyond six months of age, then the baby may have a serious neurological defect, such as a brain injury, spinal cord damage, or bleeding in the brain.
Fetuses display a grasp reflex while still in the womb, about 28 weeks into development, and the grip should be strong enough by 37 weeks that the baby’s weight can be lifted. Reflexes of the legs are similarly tested by sitting the infant upright, brushing the foot, and observing how the hip and knee flex in response. Abnormalities in this reflex can indicate defects in the brainstem and spinal cord, and can be difficult to measure in infants that are restrained by medical equipment. A reaction such as the grasp reflex normally disappears with time, although other reflexes present in babies last throughout a person’s life. These include blinking, cough, gag, as well as sneeze and yawn reflexes.
If a reflex that is typically exclusive to babies is observed in an adult, this could be a sign of serious brain damage or a stroke, calling for further testing. Neurologists are aided by reflex analysis techniques to determine whether medical testing is necessary and if there is in fact a serious problem in the nervous system. For a baby, if the grasp reflex ceases by six months, and is replaced by the usual pincer grip, then this is a sign of normal neurological development.