When babies are born, they come with several built-in reflexes. Some of these reflexes are useful—the sucking reflex helps baby eat. Some reflexes are cute—the grasp reflex causes baby’s hand to clench mom or dad’s finger if it brushes up against their palm. And some reflexes, like the Moro reflex are just downright strange.
What is the Moro Reflex?
The Moro reflex in babies, also known as the “startle reflex,” is a sudden, involuntary reaction that babies have when their body feels unsupported or when they are startled by a loud noise or sudden movement. This reaction causes babies to unsteadily and quickly reach their arms up and outwards, like they are reaching for something. Just as quickly, they bring their arms back by their sides and often start crying. Some parents mistake these weird movements for dreams or even seizures, but they are normal and a sign that the baby’s brain and neurological systems are functioning.
It turns out that the Moro reflex, although weird to see, is believed to be an evolutionary adaptation that enabled babies to cling to their mothers while carrying them around throughout the day. This reflex is also seen in baby monkeys. If a baby monkey clings to mom’s chest hair (with their backs toward the ground) as she walks on all fours and they suddenly lose their balance or feel like they are falling, they quickly reach out their arms and then pull them back to adjust their grip and ensure they don’t slip off. As mom is swinging high up in the trees, you can imagine how important it would be for a baby monkey not to fall off!
Unfortunately, this reflex doesn’t do modern human babies much good. In fact, the startle reflex can be a nuisance! Imagine you are walking down the street minding your own business when suddenly you have a powerful, involuntary twitch that causes you to suddenly jerk your limbs around. I’m sure such a thing would be very disorienting and frightening!
This fright is what happens to babies when the Moro reflex is activated. For example, a baby is resting on her back in a crib when her arms suddenly reach out and she startles herself awake. It’s not a noise or a bad dream that startled her, it’s her jerking limbs that scared her, causing her to cry, which is the opposite of helpful for a sleeping baby (and her parents) in 2017!
Deactivating the Startle Reflex
So what can you do about it and can we make the Moro reflex disappear? It turns out that simply turning a baby onto their side or stomach completely deactivates this reflex. This is believed to be because our primate ancestors did not need this reflex when not hanging from mom’s belly. So simply placing a baby on their side or completely onto their stomach, helps calm them and stop their crying.
Of course, when you place a baby on their side or stomach, you always need to be sure that baby’s airway is clear so their breathing isn’t obstructed. Simply turning baby’s head gently to one side or the other can keep their nose and mouth clear.
Another major safety tidbit is to NEVER leave baby unattended in the side or stomach position! The American Academy of Pediatrics always recommends babies are placed “BACK TO SLEEP”—i.e., baby sleeps on their back to deter SIDS risks. If you are holding baby or have your sight on baby at all times, the side or stomach position is totally natural and safe. Just like you’d never turn your back on a baby in a bathtub, side or stomach lying is fine if someone is monitoring baby’s breathing.
If you are still worried about the safety of stomach side lying for babies, just remember the time that you might have spent with baby “skin to skin” just after birth. Baby was on their tummy then and your medical providers encouraged this positioning! So babies can and should spend time in this position so long as you’ve got your “Mom / Hawk Eyes” on them at all times.
Another option to deter the Moro reflex is to use a swaddle. Something like the Baby Brezza 3 in 1 Swaddle Transition Sleep Suit can ensure that baby is safely sleeping on their back, while keeping arms tucked at their sides. Swaddling helps secure baby to prevent startling and help baby sleep for longer stretches.
Advanced Side and Stomach Positioning
Now that we know how to reduce Moro reflex let's look at positioning. Side or stomach positioning can be achieved in any number of ways like the reverse breastfeeding hold, the football hold, and even on your lap!
Some advanced positions include the “cannonball” position—similar to child’s pose in yoga—where baby’s knees are tucked up under them as they lay on tummy down on your lap, and the “hot-water-bottle position” where baby is draped over an old fashioned, warm rice pack.
The Startle Reflex in babies is nothing to worry about and now you can use side or stomach positioning as another trick in your soothing arsenal to calm a crying baby and help them to sleep. You can use it independently or in conjunction with the other soothing S’s like swaddling, sucking, or swinging. In fact, some of these positions might even put your finger in the perfect position for non-nutritive sucking. Just remember, once baby is asleep and you’re putting them into their crib to do a load of laundry, they are placed on their backs for “Back to Sleep” SIDS safety!
Written by Melissa Gersin, Infant Crying Specialist and Maternity Nurse
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