What is the Moro reflex?

From the Guidelines

The Moro reflex is a normal primitive reflex in newborns that should be present in all healthy newborns and typically disappears between 3-6 months of age. The presence of this reflex is an important neurological marker that pediatricians check during routine infant examinations, as its absence in newborns may indicate neurological problems, while persistence beyond 6 months might suggest developmental delays 1.

Key Characteristics of the Moro Reflex

• The reflex occurs when a baby is startled by a sudden movement or loud noise
• The baby throws back their head, extends their arms and legs outward, and then rapidly brings their arms together as if embracing something, often followed by crying
• This reflex typically appears by 28 weeks of gestation and should be present in all healthy newborns
• It gradually disappears between 3-6 months of age as the baby's nervous system matures

Clinical Significance

• The Moro reflex is an important indicator of neurological development and its absence or persistence may indicate potential issues
• Pediatricians check for this reflex during routine examinations to assess neurological health
• Parents can help manage the reflex by providing secure support when holding their baby, avoiding sudden movements, and swaddling, which can prevent the startle response from waking a sleeping infant

Evolutionary Perspective

• The Moro reflex is thought to have evolved as a protective mechanism, representing the baby's primitive "fight or flight" response
• It is a vital reflex that helps the baby respond to potential threats and ensures its safety
• Understanding the Moro reflex and its significance can help parents and healthcare providers better support the neurological development of newborns and identify potential issues early on 1.

From the Research

Definition and Characteristics of Moro Reflex

• The Moro reflex (MR) is a primitive reflex that disappears after the first three months of life 2.
• It is characterized by a quick extension-adduction of both arms, followed by orientation of the body, head, and eyes towards a human person, and full extension-abduction of both arms with spreading of the fingers, crying, and a distressed face 3.
• The Moro reflex is due to the activation of an archaic neural circuit present in the newborn, which is later inhibited by the upper brain structures 2.

Neural Mechanism and Location

• The neural centre underlying the MR is located in the lower part of the brainstem, as it can be elicited in anencephalic infants 2.
• The MR might involve a distinct neural circuitry, which is (or becomes) hyperexcitable as a consequence of a pathological condition (epilepsy) or physiological brain immaturity (the MR) 2.
• The neural mechanism of the Moro reaction probably involves both the fear and the separation-distress systems 3.

Phylogenetic Significance and Ritualized Behavior

• The Moro reflex has been proposed to have a phylogenetic significance as a ritualized behavior of nonverbal communication 3.
• The gestures associated with the Moro reflex, such as crying and orientation of the body, head, and eyes towards a human person, are gestures of intention to communicate and support this hypothesis 3.
• The Moro reflex may be considered as a startle reflex controlled by the neural fear system, followed by a Moro reflex as a ritualized behavior 3.

Clinical Significance and Diagnosis

• The absence of the Moro reflex during the neonatal period and early infancy is highly diagnostic, indicating a variety of compromised conditions 4.
• The grasp reflex, including the palmar and plantar grasp reflex, has diagnostic significance and is mediated by a spinal reflex mechanism 4.
• The Moro reflex and other primitive reflexes seem to be essential for the arboreal life of monkey newborns, and their interrelationship is important for understanding their phylogenetic meaning 4.