The Moro reflex is present at birth, peaks in the first month of life and begins to disappear around 2 months of age. It is likely to occur if the infant’s head suddenly shifts position, the temperature changes abruptly, or they are startled by a sudden noise. The legs and head extend while the arms jerk up and out with the palms up and thumbs flexed. Shortly afterward the arms are brought together and the hands clench into fists, and the infant cries loudly.The reflex normally disappears by three to four months of age, though it may last up to six months. Bilateral absence of the reflex may mean damage to the infant’s central nervous system while a unilateral absence could mean an injury due to birth trauma such as a fractured clavicle or injury to the brachial plexus. Erb’s palsy or some other form of paralysis is also sometimes present in such cases.A way to experiment to see if the reflex is present is to hold the infant horizontally on their back and let the head drop slightly or produce a sudden loud sound against the surface. In human evolutionary past, the Moro reflex may have helped the infant cling to his mother while she carried him around all day. If the infant lost its balance, the reflex caused the infant to embrace its mother and regain its hold on the mother’s body.