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Startle response; Startle reflex; Embrace reflex
Moro reflex is type of involuntary response that is present at birth. It normally disappears after 3 or 4 months.
See also: Infant reflexes
The Moro reflex may be demonstrated by placing the infant face up on a soft, padded surface. The head is gently lifted with enough support to just begin to remove the body weight from the pad. (Note: The infant's body should not be lifted off the pad, only the weight removed.)
The head is then released suddenly, allowed to fall backward momentarily, but quickly supported again (not allowed to bang on the padding). The infant may have a "startled" look, and the arms fling out sideways with the palms up and the thumbs flexed. As the reflex ends, the infant draws its arms back to the body, elbows flexed, and then relaxes.
This is a normal reflex present in newborn infants. Absence of the Moro reflex in an infant is abnormal. Presence of a Moro reflex in an older infant, child, or adult is also abnormal.
Two-sided absence of the Moro reflex suggests damage to the brain or spinal cord.
One-sided absence of the Moro reflex suggests the possibility of a broken shoulder bone or injury to the group of nerves that run from the lower neck and upper shoulder area. Conditions associated with such nerve injury include Erb's palsy and Erb-Duchenne paralysis. Loss of muscle function on one side of the body may also produce an asymmetrical Moro reflex.
Zafeiriou DI. Primitive reflexes and postural reactions in the neurodevelopmental examination. Pediatr Neurol. 2004;31(1):1-8.
Bear LM. Early identification of infants at risk for developmental disabilities. Pediatr Clin North Am. 2004;51(3):685-701.
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