Moro Reflex: Why Newborns Startle Easily

You can soothe your baby by holding them close

Medically reviewed by Jonathan B. Jassey, DO

The Moro reflex is a protective "primitive reflex" seen in healthy newborns and infants up to 6 months old when startled or if sudden changes in body position trigger an instinctive fear of falling. This automatic reflex is marked by a baby's arms quickly extending away from the body with palms up, fingers splayed apart, and then retracting back to the chest.

The Moro reflex gradually fades between 2 and 5 months of age and typically disappears entirely by 6 months old.

The absence of the Moro reflex during a baby's neonatal period (first 28 days after birth) and early infancy is atypical and may indicate something's wrong. On the flip side, it's also abnormal for the Moro reflex not to disappear by six months or persist during childhood.

This article covers what you need to know about why newborns startle easily, defines the Moro reflex, explains when healthy babies typically outgrow newborn reflexes, and gives some practical tips for soothing infants scared by their Moro reflex. 

Newborn Easily Startled: What Triggers the Moro Reflex?

The Moro reflex or "startle reflex" is triggered by startling stimuli such as loud noise, bursts of light, sudden movements, or abrupt changes in a baby's body or head position. Anything that intuitively causes alarm can activate a baby's self-preserving survival instincts and instantaneously trigger this reflex. Infants can even startle themselves, which triggers this reflex.

Other Newborn Reflexes That Healthy Babies Outgrow

Below are six primitive reflexes present in newborns that healthy babies typically outgrow a few months after being born:

• Grasp reflex

• Moro reflex

• Rooting reflex

• Stepping reflex

• Suck reflex

• Tonic neck reflex
  

Reasons Some Newborns Don’t Have the Moro Reflex

The complete absence of a newborn's Moro reflex on both sides of the body (symmetrical) may be the result of many things, including:

• Injury during birth

• Neurological disorder

• Congenital brain malformation

• Severe asphyxia during birthing process

• Intracranial hemorrhage (brain bleed)

• Infection

• Muscular weakness

• Spastic cerebral palsy

Asymmetrical Moro reflex reactions (occurring on only one side of an infant's body) may be due to a local injury, such as a broken collarbone, damage to a peripheral nerve, or a cervical cord problem.

When Do Newborns Grow Out of the Moro Reflex?

Newborns typically grow out of the Moro reflex about 8 to 12 weeks after birth. Between 2 and 5 months of age, it's normal for the Moro reflex to disappear gradually. Persistence of the Moro reflex beyond 6 months of age is considered abnormal and would be regarded as too long for this primitive reflex to last.

Moro Reflex at Newborn Checkups

Triggering a falling sensation by quickly lowering an infant (while being held safely just a few inches above a padded examination table) is the most common way to test for the Moro reflex during newborn checkups. 

A professionally trained examiner may also elicit the Moro reaction following the "pull-to-sit" maneuver by slowly lowering the newborn's torso until there's a very small gap between the neck and a cushioned surface and letting go so the infant falls back suddenly. When testing the Moro reflex, startling the baby and suddenness are key.

Because Moro reflex tests can potentially cause harm, they should only be conducted by a trained healthcare provider. Some childhood development researchers believe that even professionals should avoid purposely stimulating newborns' fear systems by startling them or unnecessarily triggering their Moro reflex using drop tests that trick newborns into thinking they're falling.

Soothing Baby Scared by the Moro Reflex

Because the Moro reflex is a startle reaction typically caused by a falling sensation, an effective way to soothe a baby scared by this self-protective primitive reflex is to hold them close and make them feel safe. Soothing a baby spooked by its Moro reflex with physical contact is comforting and promotes attachment security during infancy.

Also, because bright light and loud noise are stimuli that trigger the Moro reflex, quiet and dimly lit spaces that feel serene can soothe a baby's nerves and reduce the frequency of startling Moro reactions.

That said, there's no need to try to stop an evolutionarily preserved primitive reflex like the Moro reaction from occurring during early infancy. It's happening for a reason and should be outgrown in two to six months.

Summary

The Moro reflex is a protective reaction that happens automatically when newborns are scared or afraid they might fall. It typically starts to disappear when a baby is 2 or 3 months old and is usually totally gone when infants reach 6 months of age. Holding a baby close and making them feel safe calms the Moro reflex.