What Is the Moro Reflex in Babies?

The Moro reflex is one of the reflexes babies are born with, and you're likely to spot this involuntary response soon after birth. Find out what the medical definition is, what triggers this reflex, and what you can do to help calm your baby if needed.

What Is the Moro Reflex?

The Moro or “startle” reflex is an automatic or involuntary reflex in newborns and infants in which a baby suddenly flings her arms sideways with her hands flexed, throws out her legs, extends her neck, and just as suddenly brings her arms together and may begin crying. The Moro reflex usually occurs in the following instances:

• If your baby’s head shifts positions abruptly

• If his head falls backward

• If he’s startled by sudden stimulation, like a loud noise

• If his body’s balance is disrupted, as a result of an abrupt movement.

Note that in premature babies, the Moro reflex may be weak initially.

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Is There a Way to Calm Your Baby’s Moro Reflex?

In some instances your baby may startle himself awake during sleep because of the Moro reflex. To help prevent this, you could swaddle your baby at bedtime. This involves wrapping him in a swaddle blanket, much like a burrito. See the image below for a step-by-step, how-to guide:

Learn more about swaddling your baby here.

How Long Does the Moro Reflex Last and When Does It Disappear?

The Moro reflex usually appears in your baby's first few weeks, peaking in her first month before disappearing after 2 months of age. Eventually, as this reflex disappears, your newborn's movements will become more intentional.

How Do You Test for the Moro Reflex?

Your healthcare provider will test your baby for the Moro reflex soon after birth and during well-child visits. To do so, after placing your baby face-up on a soft, padded, surface, the provider will gently lift your baby’s head and then quickly release it, supporting her head again as it falls backward for a moment. Your baby may then look startled, throw out her arms, and cry for a short while. Your baby will draw her arms in and eventually relax. If your baby has a different response, such as a Moro reflex that is overly exaggerated or asymmetric, meaning that he doesn’t respond equally with both arms, the healthcare provider may perform an examination and/or order further tests to determine what’s causing the atypical response.

What Does It Mean if Your Baby Still Has the Moro Reflex?

Every baby develops at his own pace, so it’s OK if your baby’s Moro reflex continues past 2 months. However, if you notice your baby still has the Moro reflex after 4 months, consult his healthcare provider. It may be a sign of a developmental delay. The healthcare provider will evaluate your baby’s case and come to a determination based on various other assessments and tests.

The Bottom Line

The Moro reflex is an involuntary “startle” reflex that your baby has as early as her first few weeks, lasting until about the time she’s 2 months old. It eventually will disappear. Sometimes babies may have the Moro reflex at night during sleep. To help prevent your baby from startling himself awake, consider swaddling him. If your baby’s Moro reflex continues past 4 months of age, speak to your healthcare provider. It may be a sign of developmental delay. However, since every baby develops at an individual pace, your baby may stop having the Moro reflex earlier or even later.

_{How We Wrote This Article The information in this article is based on the expert advice found in trusted medical and government sources, such as the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists. You can find a full list of sources used for this article below. The content on this page should not replace professional medical advice. Always consult medical professionals for full diagnosis and treatment.}