Moro reflex: characteristics and clinical implications in babies

Reflexes are involuntary responses of the body to stimulation, that is, unintentional. These indicate a state of health within normality. There is a great variety of primary reflexes, which appear at birth.

In this article we will know one of them, the reflection of the Moro, a reflex seen at birth, which usually disappears by 3-4 months. Its persistence or absence usually indicates abnormalities or alterations in development.

Related article: "The 12 primitive reflexes of babies"

Origin of the Moro reflex

The Moro reflex, also called the "baby startle" reflex, is a primary reflex named after the Austrian pediatrician Ernst Moro, which he was the one who first described in Western medicine. Its presence in the indicated period indicates normal development in the newborn, and the presence of health.

Ernst Moro (1874 - 1951) was an Austrian physician and pediatrician who studied medicine in Graz, Austria, earning his M.D. in 1899. As we have seen, he not only described Moro's reflection for the first time, but he discovered it and gave it a name.

When does it appear?

When a baby is born, the hospital checks that it has some important primary reflexes, including the Moro reflex.

More's reflection fully seen in newborn babies, who are born after the 34th week of pregnancy, and incompletely in those who are born preterm after the 28th week.

This reflex extends until 3 or 4 months of life. Its absence or persistence may indicate neurological defects or disorders of the nervous system.. During the first 4 months, the pediatrician will continue to check at visits if the child continues to have the reflex. Even beyond these months, because, as we will see in detail later, the persistence of the reflex beyond 4 or 5 months can indicate certain neurological defects.

• You may be interested in: "What should my baby do the first month after birth?"

What does it consist of?

To see how the Moro reflex appears, the baby should be placed on his back on a soft, padded surface. The baby's head is gently raised with sufficient support and the weight of the cushion is started to be taken off; that is, the baby's body is not lifted off the cushion, only the weight is taken off. After head snaps loose, falls back momentarily, but it holds up again quickly, not allowing it to hit the padded surface.

The normal thing then is that the baby responds with a startled look; Her arms will swing to the sides with her palms facing up and her thumbs flexed. The baby may even cry for a minute.

That is, the Moro reflection appears when the baby feels a lack of support (It can also appear before a sudden change of position). When Moro's reflex ends, she does it this way; the baby draws the arms in towards the body, with the elbows flexed, and finally relaxes.

alterations

The absence or persistence of the Moro reflex indicates certain alterations in normal development:

1. absence of reflex

The absence of the Moro reflex in an infant is abnormal, and may suggest, for example, damage to the brain or spinal cord. On the other hand, if it occurs only on one side, there is the possibility of a fractured clavicle or damage to the brachial plexus nerve group.

• You may be interested in: "Spinal cord: anatomy, parts and functions"

2. reflex persistence

If the Moro reflex persists beyond the fourth or fifth month of age, it may also indicate severe neurological defects. This is why its existence continues to be verified in pediatrician consultations.

its phases

But what does the Moro reflex mean in the context of an integrated evaluation of the central nervous system? let's see first components involved in reflex:

• The startle reflex.
• The movement of the arms in abduction.
• The movement of the arms in adduction.
• Usually crying.

Thus, the absence of these components (with the exception of crying) or an asymmetry in the movements is not normal. Nor is the persistence of these components in children and adolescents a good sign..

On the other hand, some people with cerebral palsy may present the Moro reflex in a persistent and exacerbated way. As we have seen, abnormalities in its manifestation indicate brain or spinal cord disorders.

Syndromes with altered reflex

Some of the syndromes with an abnormal Moro reflex are Erb-Duchenne's palsy (upper brachial plexus palsy); He presents with an asymmetric Moro reflex, caused by a shoulder dystocia.

Another syndrome, this time with an absent Moro reflex, is DeMorsier syndrome, which includes optic nerve dysplasia. This syndrome occurs with the absence of the reflex as part of specific complications not related to the shoulder and its nerves.

Finally, the absence of the Moro reflex is also detected in newborns with Down syndrome and in newborns with perinatal listeriosis. The latter consists of an infrequent infection, related to the ingestion of contaminated food and that can have serious consequences for the mother and the newborn.

Bibliographic references:

• García Madruga, J.A.; Devall, J. (2010). Developmental Psychology I. Cognitive and linguistic development. UNED. Madrid
• MedlinePlus. (2019). Moorish reflection. Medical encyclopedia.
• Paris, E. (2014). The Moro or startle reflex in the baby. Babies and more.