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Alternative Names Return to topStartle response; Startle reflex; Embrace reflex
Definition Return to top
Moro reflex is type of involuntary response that is present at birth. It normally disappears after 3 or 4 months.
See also: Infantile reflexes
Considerations Return to top
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.
Causes Return to top
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.
Home Care Return to top
It is not necessary to check for a Moro reflex at home. Your doctor will check this reflex during an office visit.
When to Contact a Medical Professional Return to top
Call your health care provider if you think your baby may have a broken shoulder bone or injury to the nerves that run from the lower neck and upper shoulder area (brachial plexus injury), which can cause the loss of the Moro reflex on one side.
What to Expect at Your Office Visit Return to top
An abnormal Moro reflex is usually discovered by the health care provider. The health care provider will perform a physical exam and ask questions about the child's medical history. Medical history questions may include:
If the reflex is absent or abnormal, further tests may need to be done to examine the child's muscles and nerves. Diagnostic tests, in cases of decreased or absent reflex, may include:
References Return to top
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.Update Date: 11/9/2007 Updated by: Deirdre O’Reilly, M.D., M.P.H., Neonatologist, Division of Newborn Medicine, Children’s Hospital Boston and Instructor in Pediatrics, Harvard Medical School, Boston, Massachusetts.