Babies are pretty darn smart right from the start. Healthy babies are born with basic motor responses, known as newborn reflexes, that help them survive and thrive in their brand new environment.
Some of these baby reflexes may be subtle, while others, like the Moro reflex (aka the startle reflex), are pretty hard to miss. But they're all incredibly important and tend to have a specific purpose — which is why the pediatrician will check them at your baby's first doctor's visit a day or two after birth.
Here’s what you need to know about the Moro reflex, including what it looks like and why it happens.
What is the Moro reflex?
The startle or Moro reflex is a hard-wired response in your newborn to something unexpected — a loud noise, say, or the sensation of falling. It often happens when your baby is sleeping, but can also occur while he's awake.
If your baby is exhibiting the Moro reflex, you’ll know it. He’ll suddenly arch his back, fling his arms up and out, and open his hands. Then your little one will draw up his knees and bring his arms and re-clenched fists close to his body — almost as if he’s giving himself a hug. Seconds later, as abruptly as the startle started, it’s over, though your baby may also cry.
While it may be jarring to you at first until you get used to it, it doesn't bother your baby at all and is an indication that he's healthy and developing as he should. Think of it as your newborn’s first attempts to protect himself and regain his sense of balance.
And don't worry — the Moro reflex isn't bad for your baby and typically goes away in a few months. One downside, however, is that newborns can startle themselves awake and then have a hard time settling back down (sometimes even crying a lot as a result). But babies often aren't bothered by it at all and fall back to sleep right away, as if nothing ever happened.
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How long does the Moro reflex last?
The Moro reflex starts at birth — and in fact, your practitioners will check for it in those first hours after your baby is born. It usually lasts for a few months. While every baby is different, most parents notice their little one's startle reflex peaking in the first month and beginning to fade at around 2 to 4 months, disappearing completely by 6 months or so.
But even earlier, when your baby is about 6 weeks old, he’ll start to acclimate to life on the outside and feel more secure in his surroundings (thanks to you).
In the meantime, don’t sweat the startles, as they’re a sign of healthy neurological development. But do try to offer your infant lots of extra support when you’re toting him from one place to another.
What triggers the Moro reflex?
Just about everything is unfamiliar to newborns, so they're easily surprised and even frightened by new-to-them sensations and sounds. Here are some of the things that may trigger the Moro reflex:
Your newborn thinks he’s falling, like when you put your little one down in his bassinet without enough support (don’t worry, it happens)
Any unexpected movement— for instance, you scoop your baby from his car seat or shift the position of his head
Loud, sudden noises nearby — like a dog's piercing bark, an ambulance wailing down the street or something dropping and crashing to the floor
Your baby jerks his arms or legs and startles himself
- Very bright lights, especially when they're flicked on in a previously dark or dim room
No apparent reason at all, though if it's when he's asleep, he might have been dreaming of falling
Doctors check for the Moro reflex because it’s a sign that your baby’s nervous system is working.
While your baby is on his back, the pediatrician will either gently pull on your little one's arm to lift his shoulders slightly up off the padded examining table and then let go, or slowly lift your baby's head with a hand and suddenly release it, but then support the head quickly so it doesn't hit the padded table.
Both little tests can produce the sensation of falling, and will likely cause your baby to startle or have a startled look on his face (and possibly even cry) if his Moro reflex is normal.
How to stop your baby from startling
You can’t entirely get rid of the startle reflex and wouldn't want to — after all, there’s a reason Mother Nature included it with the rest of the primitive responses babies are born with. And remember that the Moro reflex does begin to fade on its own after a few months as your baby gets more used to the world and his nervous system matures.
Still, there are ways for you to help your baby stop startling awake, including:
Hold your baby close
Babies startle when they’re jostled suddenly. So be gentle when you pick up your cutie and put him down, and try to keep his neck and head supported with your hand. You won’t always succeed in nixing the startle response, but soon you’ll become a pro at holding your baby securely.
Try swaddling
Swaddling is the art of wrapping your baby up in a blanket so he looks like a tiny burrito. A tight-but-not-too-tight swaddle keeps him from flailing his arms and legs so he sleeps more soundly.
You can get a swaddling tutorial at the hospital or online, or make it easier by buying a swaddle blanket with Velcro tabs. You can also opt for a sleep sack or a sleep/swaddle sack instead for naptime and bedtime. Just be warned: Not all babies like being confined, so some take to swaddling better than others. And remember you'll have to stop swaddling if your baby is wriggling out of the blanket or showing signs of rolling over (usually around the 3- to 4-month mark), as it can pose risks for your little one.
Turn down the noise
If you can, tread lightly and quietly around your baby, especially when he's snoozing. You can’t stifle every sound, but you can minimize the din with a white noise machine or fan until the sounds of your home and surroundings are more familiar to your newborn.
When to call the doctor
Your baby’s health care provider will probably be the one to discover if your newborn has no Moro reflex at all, or if it seems abnormal in some other way.
One caveat: Preemies often don’t have a well-developed Moro reflex or it may appear weaker, so you may not recognize it when your premature baby startles.
But if you notice anything amiss with your baby or any changes between doctor's visits, be sure to contact your pediatrician as soon as possible. Signs to look for include the following:
Your baby is no longer showing signs of the reflex, which might indicate some sort of brain or spinal cord damage.
- Your baby can only move one side of his body, which might mean his shoulder is broken or the nerves that run down his neck to his arm are damaged.
What happens if the Moro reflex doesn’t go away? Remember, babies develop at their own pace. That said, if your older baby still has the Moro reflex well past about 6 months, there may be something more serious going on. Get in touch with your pediatrician, who will be able to perform a test to find out if there's anything wrong.
In the meantime, try not to jump every time your baby jumps! Those startles are a good sign, even if they do come with some cries. Soothing your baby will make him feel more secure, and pretty soon, the Moro reflex will be a thing of the past.
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