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A reflex is a type of involuntary (without trying) response to stimulation. The Moro reflex is one of many reflexes that are seen at birth. It normally disappears after 3 or 4 months.
Startle response; Startle reflex; Embrace reflex
Your baby's doctor will check for this reflex right after birth and during well-child visits.
To see the Moro reflex, the child will be placed 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 for a moment, but quickly supported again (not allowed to bang on the padding).
The normal response is for the baby to have a startled look. The baby's arms should move sideways with the palms up and the thumbs flexed. The baby may cry for a minute.
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.
A Moro reflex in an older infant, child, or adult is abnormal.
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:
Zafeiriou DI. Primitive reflexes and postural reactions in the neurodevelopmental examination. Pediatr Neurol. 2004;31(1):1-8.
Lehman RK, Schor NF. Neurologic Evaluation. In: Kliegman RM,Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 584.