From the Research
The reflex characterized by abduction and upward movement of the arms, followed by adduction and flexion, when an infant's head is moved back suddenly is the Moro reflex. This reflex is observed in newborns when their head is allowed to fall backward slightly while being supported, causing a sudden change in position. In response, the infant exhibits a characteristic startle reaction where the arms abduct (move away from the body) and extend upward, followed by adduction (movement toward the body) and flexion, often accompanied by crying. The Moro reflex is a normal primitive reflex present at birth that typically disappears by 3-6 months of age, as noted in a study published in 2022 1. It's an important neurological sign that healthcare providers check during infant examinations to assess normal brain and nervous system development.
Some key points about the Moro reflex include:
- It is a primitive reflex that disappears after the first three months of life 1
- The neural centre underlying the Moro reflex is located in the lower part of the brainstem 1
- The Moro reflex is due to the activation of an archaic neural circuit present in the newborn, the activity of which is later inhibited by the upper brain structures 1
- Persistence of this reflex beyond 6 months may indicate potential neurological issues that warrant further evaluation, as suggested by studies on primitive reflexes and postural reactions in the neurodevelopmental examination 2
The Moro reflex has been studied in various contexts, including its relationship to other primitive reflexes and its potential implications for neurological development. For example, a study published in 2011 found that the sucking, Babinski, and Moro reflexes were present in high-risk newborns, but with varying frequencies and relationships to clinical variables 3. Another study published in 2008 suggested that isolated absence of the Moro reflex may reflect underlying abnormalities of the vestibular system 4. However, the most recent and highest-quality study on the topic, published in 2022, provides the most relevant information on the Moro reflex and its characteristics 1.
In terms of clinical significance, the Moro reflex is an important indicator of normal brain and nervous system development in infants. Healthcare providers should be aware of the typical presentation and duration of the Moro reflex, as well as its potential implications for neurological development. As noted in a study published in 1995, the Moro response is a complex movement pattern that involves the coordination of multiple muscle groups and is influenced by the infant's behavioral state 5. Overall, the Moro reflex is a critical component of the neurodevelopmental examination and should be carefully evaluated in infants to assess their neurological development and identify potential issues early on.