Moro reflex is one of the prime infantile reflexes, named after Ernst Moro, an Austrian pediatrician who was the first to describe it. This survival reflex is seen in newborns where they make a startling gesture in response to any danger sensed by them [1, 3].
Moro reflex is a part of the infant’s neurological development occurring due to release of certain chemicals like cortisol and adrenaline. They display it through four distinct actions that include [1, 5, 7]:
Being inherent in newborns, it helps them shield themselves from any danger. They respond with a startled expression at the slightest sound or disturbance like ringing of the door bell, whistling sound of a kettle, sound of a vacuum cleaner, being touched while they are sleeping, loud noise made by others or feeling that they will fall or be dropped .
Along with other tests, infants are checked by the health care provider to see if their Moro reflex is functioning well or not. The baby is placed on a soft padded mat with his head and shoulders being raised gently. The doctor at an instant releases the head for a fraction of a second and supports it again. The baby will pose a startled look and react to the sudden change by stretching out his arms as well as opening up the palms [1,2] .
This video highlights how a five-day-old infant gives a startling expression along with characteristic motor movements on sensing that he may fall.
The reflex starts developing at about nine weeks of gestation, but babies born prematurely after 28 weeks have it in an incomplete form. However, by the 34th week, this reflex is fully developed [1, 8]. This form of the fight-or-flight response remains with infants till they are three or four months old.
Newborns having a deformity in their motor development, a damaged spinal cord, dysfunctional central nervous system, birth asphyxia, weak muscles, injury during birth or intracranial hemorrhage do not have this reflex at all . If the reflex is present on one side, then the infant might be suffering from a fractured shoulder. A condition named brachial plexus palsy is also responsible for the partial formation of this reflex, where the nerves running from the neck to the shoulder on one side are damaged .
Infants suffering from intrauterine complications like hydranencephaly (a brain disorder) or hyperekplexia (a neurological genetic disorder) show a more prominent or exaggerated Moro reflex. In this condition, the infant tends to spread and pull back his arms at frequent intervals [9,10].
Neonates may develop hyperactive Moro reflex characterized by jittery and jerky arm movements if the mother indulges in drug abuse during pregnancy .
Children who have retained their Moro reflex for a longer time show certain symptoms [15, 16] :
According to studies, retained Moro reflex in the mother making her anxious and fearful also affects the child. Apart from this, a high risk or traumatic pregnancy are other possible causes . Children suffering from cerebral palsy, where the movement of the body and coordination of the muscles is affected, also retain their Moro reflex .
If your child has retained this reflex, then consult a doctor immediately as it can be cured by various therapies and counseling if addressed at an early stage.
Moro reflex is often confused with startle reflex because of the similarity in their mechanism. Infant Moro reflex is present for some weeks after birth, being replaced by startle reflex that stays with an individual throughout his lifetime, protecting him from any sudden danger [13, 14].
This reflex is sometimes mistaken for infantile spasms that is observed in babies between four and eight months of age. Infantile spasm commonly starts after waking up or feeding, occurring in clusters with 100 spasms in one go, along with unusual rapid body and arm movements [11,12].
Though Moro reflex in newborns goes away in some time, you can swaddle your baby hugging him gently to provide a sense of comfort and security whenever he gets startled.
Published on March 10th 2015 by Pregmed Editorial Team.
Article was last reviewed on 8th September 2015.