Moro reflex is elicited by the sudden dropping of the infant's head in relation to the trunk. It results in abduction and extension of the infant's arms and opening of the hands, followed by flexion. It is present starting at 32 weeks gestation, well-established by 37 weeks gestation, and disappears by three to six months of age 1.
If Moro reflex is absent bilaterally, the differential diagnosis may include CNS depression by narcotics or anesthesia, brain anoxia, or a very premature baby.
While if the Moro reflex is asymmetrical, the differential diagnosis may include Erb's palsy, fracture of the clavicle, or hummers.
If it persists beyond the 6th month, it indicates CNS damage.