Moro Reflex in Babies: What To Expect During the Newborn Stage

As a first-time parent, I was enamored with all of the little quirks my brand new baby had. But one movement I was unprepared for? The Moro reflex. This seemingly random reflex looked like a mix of a strange dance move combined with a surprised reaction. No wonder the Moro reflex is often called the "startle reflex," according to the American Academy of Pediatrics (AAP).

So what exactly is the Moro reflex, and why do babies have it? Also, does the Moro reflex ever indicate a problem with development? Here's everything you need to know, according to experts.

What Is the Moro Reflex?

The Moro reflex is an involuntary protective motor response that you'll see in newborns. It's especially apparent "when there is a sudden loud sound, or they experience a sudden change in movement, such as being lowered into the crib," says Emma Hubbard, a pediatric occupational therapist and the founder of Brightest Beginning.

When the Moro reflex is triggered, "the newborn will instinctively throw their head back, stretch the arms and legs outwards, and may even let out a cry," says Hubbard. After that, they quickly draw their arms and legs back toward their bodies.

For the visual learners, a nurse, who posts as @RegisteredNurseRN to more than 2 million YouTube subscribers, shared a video of a baby displaying the Moro reflex.

Why Do Babies Have a Moro Reflex?

The Moro reflex may look startling to new parents—no pun intended. But it's actually a good sign when a newborn does it.

"The presence of a Moro reflex at birth indicates the baby's nervous system is functioning and maturing correctly," explains Hubbard. "The Moro reflex will gradually fade as the infant grows and develops more control over their muscles and movements. The fading of this reflex also indicates that the baby's nervous system is continuing to mature."

The Moro reflex's connection to the nervous system is part of the reason why preterm infants can have a weaker one. "Their nervous system might not be fully mature yet," says Hubbard. "Their motor skills and muscle tone are still developing, making the reflex response less noticeable."

What Age Does the Moro Reflex Start?

Expectant parents don't know it, but the baby actually develops the Moro reflex during pregnancy. "The Moro reflex starts to develop in infants around 25 to 28 weeks gestation," says Hubbard. "It continues to mature throughout the remainder of the pregnancy and is typically fully present at birth in full-term infants."

When Should the Moro Reflex Go Away?

Eventually, your baby will outgrow the Moro reflex. That usually happens at 2 months, although it can sometimes go up to 6 months of age. It's when "the baby's nervous system matures, and they develop more control over their movements," says Ashley Elmer, DC, CACCP, a perinatal and pediatric chiropractor and doula.

It can be a red flag if a baby never has the Moro reflex or it disappears before two months. Some potential reasons for this premature disappearance or lack of emergence include:

• Brain injury. An injury to the brain may occur in the womb or during birth. "It could affect the baby's nervous system and consequently impact the Moro reflex," says Hubbard.
• Nerve or muscle problems. "Weakness in the muscles or issues with the nerves responsible for the Moro reflex might result in a diminished or absent response," says Hubbard.
• Congenital disorders. There are some congenital disorders affecting the nervous system, muscles, or bones which can cause a weak or absent Moro reflex.
• Infections. "Certain infections, especially those that affect the nervous system, might cause a reduced or absent Moro reflex," says Hubbard.

On the flip side, some parents may notice it doesn't disappear after six months. "This is known as a retained Moro reflex, and it can be an indication of neurodevelopmental delay," says Elmer.

Speak with your provider if you're concerned about the Moro reflex, whether you feel your baby doesn't have it, it faded too soon, or the child hasn't lost it after six months. "Your pediatrician can perform a physical exam, discuss baby's medical history, and determine if any additional testing or evaluation is needed," says Elmer.