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Moro reflex

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Definition:

Moro reflex is type of involuntary response that is present at birth. It normally disappears after 3 or 4 months.

See also: Infantile reflexes

Alternative Names:

Startle response; Startle reflex; Embrace reflex

Considerations:

The Moro reflex may be demonstrated by placing the infant face up on a soft, padded surface. The head is gently lifted with enough traction 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.

Common Causes:

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 central nervous system (brain or spinal cord).

One-sided absence of the Moro reflex suggests the possibility of a fractured clavicle or injury to the brachial plexus , which can occur because of birth trauma. Conditions associated with brachial plexus injury include Erb's palsy and Erb-Duchenne paralysis . Paralysis on one side of the body may also produce an asymmetrical Moro reflex.

References:

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.

• Review Date: 5/10/2006
• Reviewed By: Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor of Pediatrics, NYU School of Medicine, New York, NY. Review provided by VeriMed Healthcare Network.

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