Moro Reflex: How to Test & How Long It Lasts

The Moro reflex is an involuntary movement seen in newborns during their first few months of life. It happens when a baby’s arm muscles react instinctively to a feeling of insecurity, such as losing balance or being startled by a sudden movement. This response is a natural sign of the body’s protective reaction to unexpected stimuli.

This reflex is similar to the reaction that older children and adults experience when they feel like they’re falling, and it shows that the baby’s nervous system is developing properly. Doctors typically test the Moro reflex right after birth and may repeat it during early pediatric visits to check that the nervous system is functioning as it should. If the reflex is missing or continues for too long, it may signal a developmental concern that needs to be assessed.

Normally, the reflex fades as the baby grows and gains more control over body movements. However, if it persists beyond the expected timeframe, it’s important to consult a pediatrician to make sure development is on track.

How the reflex test is done

The simplest way to test the Moro reflex is to hold the baby with both hands, supporting the back, neck, and head. Then, the baby is gently allowed to drop just one to two centimeters, without removing support, to create a mild startle.

When this happens, it’s normal for the baby to first extend the arms outward and then quickly bring them back toward the body, relaxing once they realize they are safe.

How long the Moro reflex lasts

The Moro reflex usually lasts until about 3 months of age, although some babies may retain it a little longer, depending on their rate of development. According to the American Academy of Pediatrics (AAP), the Moro reflex typically disappears by around 4 to 6 months of age as the infant’s nervous system matures and voluntary motor control improves. Because it’s a primitive reflex, it should disappear before the second half of the first year of life.

If the reflex is still present after 5 months, parents should see a pediatrician for a neurological evaluation to rule out any developmental problems.

What the absence of the reflex means

If a baby doesn’t show the Moro reflex, it may be linked to:

• Brachial plexus nerve injury

• A collarbone or shoulder fracture that puts pressure on the brachial plexus

• Intracranial bleeding

• Nervous system infection

• Brain or spinal cord malformation

When the reflex is missing on both sides of the body, it could indicate a more serious issue, such as brain injury. However, if it’s absent in only one arm, the cause is more likely a local problem involving the brachial plexus.

In these cases, the pediatrician may refer the baby to a pediatric neurologist for further testing, which might include shoulder X-rays or a CT scan to identify the cause and start appropriate treatment