How Can Startle Reflex Affect Your Baby - And What to Do About It!

How Can Startle Reflex Affect Your Baby - And What to Do About It!


How Can Startle Reflex Affect Your Baby - And What to Do About It Hero Image

New babies are easily startled by noises and sudden changes of movement, which can often cause them to respond in a very distinct way. And while you might have been aware of this behavioural tendency even before you become a parent, you may not have known the name for it: the Moro reflex.

When your baby experiences something “startling” and suddenly extends their arms and legs, arching back their bodies and then curling everything in again, this is an involuntary reflexive movement that all babies experience at some point in their natural development. 

While it’s completely normal, the startle reflex can cause your baby to wake up and start crying after experiencing a feeling that is probably something like falling. As well as causing some momentary distress and requiring some comforting from an adult, their sleep will likely be disturbed until they can calm down again.

As such, knowing more about the Moro reflex and ways to reduce it from happening can be useful. We explore this topic and dive into some of the science behind this curious reflex.


Understanding Newborn Reflexes

The Moro reflex is just one of many baby reflexes designed to help babies survive when they’re infants. This is a reaction produced involuntarily as your baby’s central nervous system automatically triggers a response to a specific stimulus, ordering your baby’s muscle to move and contract in a certain way. 

You can imagine this as a kind of alarm that is triggered when a baby is subjected to excessive and sudden stimulation via the senses (noises, sounds, movement). As their awareness and motor skills are not developed enough to perform any protective or stabilizing movements consciously, your baby will issue some automatic set reactions to changes in the environment aimed to help protect them from the cause of whatever sound, movement, or change they’re reacting to.

When their brain has matured by around 4 to 6 months of age, this startle reflex and other primitive reflexes should be replaced by movements which are conscious and voluntary. Other reflexes you can look out for include: 


A reflex that helps your baby to find food. If you gently touch their cheek, your baby will turn their face and open their mouth to accept food from the hand or breast. 


All babies naturally know how to suck. They will automatically start to suck if something that is touched to the roof of their mouth, in order to receive food and nourishment. It is only later that they will accept (or refuse) food voluntarily.


This reflex helps babies hold onto things without them completely slipping through their hands. If you pass a finger or toy through their palm, you’ll witness them instinctively clutching it by contracting their fingers. 


It takes a while for children to learn how to walk, but until that point, they’ll have a reflex that helps them develop their motor skills and muscles in preparation for this milestone. This “stepping” reflex is exhibited when you hold your baby upright and let their feet touch a flat surface, when they’ll start to pick up their feet in a stepping-like movement. 

All these reflexes are a normal part of a baby’s development and will help them to grow and function as toddlers with more motor skills and awareness of their movements.


Identifying the Startle Reflex

Doctor helping mother identify startle reflex in baby


If you want to check that your child is exhibiting a normal Moro reflex response, you can easily look for certain signs. For example, the first stage involves them jolting awake (if they were sleeping) and stretching out their arms and feet. You can see your baby's hands jerking up and then outwards. 

This is then followed by a contracting of sorts, where they will be looking to cling to what is close with their limbs. Your baby will bring their arms together, clench their hands into fists, and may yell in protest. Triggers of the Moro reflex include: 

  • A sudden change in the position of your baby’s head
  • An abrupt temperature change
  • A startling noise
  • A sudden touch
  • A change in lighting conditions

The reflex reaches a peak around 1 month and starts to disappear when they turn 2 months old. And when your baby reaches 6 months of age, it should have disappeared entirely, replaced by conscious and voluntary movements. Most children will phase out the reflex by 3-4 months. 


What Are Normal and Abnormal Responses?

The Moro reflex can be elicited in all normal term infants during the first 12 weeks of age, eventually phasing out with age. Studies show however that the absence or diminution of the Moro reflex within 2 to 3 months of age and the persistence of the response beyond 6 months of age can be regarded as “abnormal”.

If you are concerned about your child’s response, it is advised to see a doctor. However, keep in mind that the extent to which children will exhibit any and all of the reflex movements can vary significantly (stretching out limbs, clutching hands etc.) depending on various factors like age and development rate. 

Don’t be overly concerned if you haven’t noticed your baby’s startle reflex. Your doctor should be able to determine whether their reflex is present and normal with some simple checks. 


What Happens If the Moro Reflex Doesn't Stop?

Father with child crying from the Moro startle reflex


Reflexes should naturally phase out and be replaced by controlled movements. This is one of the clearest signs that your baby's cognitive, motor skills, and central nervous system are developing as they should.

Research has shown that for children who retain certain primitive reflexes, such as the Moro reflex, it can become harder for them to develop more mature control of their limbs and may find activities like running or catching objects difficult. 

One study that collected data from 35 children aged 4 to 6 from a Lower Silesia preschool in Poland suggests that this can also lead to difficulties in social and educational life and children may also face challenges related to attention deficit hyperactivity disorder (ADHD).

Again, before you panic about your child falling outside of the “normal” range, remember that development rates, age, and other factors unique to your child can all influence the way your child experiences their reflexes. A doctor is the best person to consult for advice and reassurance on this topic. 

How Long Does the Moro Reflex Last?

As mentioned, the startle reflex gradually gets better and typically completely disappears by month 6. This should coincide with improvements in overall balance and mobility. Below is a rough guideline.

0-1 Month

The Moro reflex is present at birth and your child should exhibit all the normal responses to sudden movement and other stimuli, such as jolting, stretching out limbs, and clenching their fists. 

2-3 Months

Some of the responses you first witness your child making may start to disappear or become less exaggerated. You may also be able to calm your child down much faster after they wake up from the Moro reflex.

4-6 Months

As your baby shows more and more improvements with their mobility and muscle strength, with decent coordination with their hands, you’ll see the responses from the startle reflex start to disappear completely.


How to Reduce Baby Startling?

There’s no way of actually stopping the Moro reflex from kicking in. However, as this reflex often leads to your baby waking up, crying, and generally feeling a bit distressed, a number of measures can be taken to make it easier and faster for your baby to relax afterwards.

Your go-to strategy should be to give your little one a hug and soothe them as you normally would when they’re feeling upset, but there are also a number of other ways to prevent the startle reflex from ruining your child’s mood and ability to sleep well. 

There’s no way of actually stopping the Moro reflex from kicking in but there are several measures that can be taken to make it easier and faster for your baby to relax afterwards.

Create a Relaxing Bedroom Environment

Creating a space where your little one can establish a healthy sleeping habit and feel relaxed and safe can help you calm them down after they experience the Moro reflex. By addressing several important environmental factors, including noise levels, lighting, and temperature, you can remove the triggers that would cause your baby to startle in the first place. A few tips include:

For more advice on creating the perfect atmosphere for your child to sleep in and feel relaxed, take a look at our popular blog:

Reduce Baby Startling: How to Create the Perfect Bedroom Atmosphere!


Mother using swaddle wrap to counteract startle reflex


Swaddling is an incredibly effective practice used to soothe babies around the world and help them sleep. Replicating the comfortable restriction of the womb, it can help to calm babies down as well as reduce the effect of the Moro reflex.

This is because the way the garment wraps around the baby’s body will restrict the baby's movements and help draw their extended limbs back after their reflex kicks in, immediately helping them to feel comforted and safe.

If your child is too old for the swaddle, or they simply don’t feel comfortable in one, don’t worry. There are also plenty of swaddle alternatives on the market that offer infants more freedom of movement while also giving them enough restriction and enclosure to make them feel cozy and comfortable, perfect for when their startle reflex kicks in. 

Our very own Zipadee-Zip, for instance, can offer your baby a secure and easily adjustable swaddle alternative that keeps them snug and offers them more flexibility than a typical swaddle.

If your infant is showing signs of discomfort in the swaddle and you still want to curb the effects of the Moro reflex, swaddle transition products can help induce the same relaxed sensation and encourage sleep, while also reducing the frequency of your baby startling.

Reduce Unnecessary Stimulation

Studies suggest that the onset of sleep is much more challenging for individuals exposed to higher levels of light, sound, or physical activity during the day. By reducing unnecessary stimulation, you may be able to help your child reach a calmer more restful state much faster, whether they’ve just experienced the startle reflex or if you’re trying to put them down for bed. 


A Healthy Evening Routine

Parent relaxing distressed baby crying from startle reflex


Routines are also incredibly useful at calming babies down who may suffer from spontaneous or sudden bouts of crying and distress caused by their Moro reflex. Creating the right environment will help establish a consistent sleep pattern and train your child to know when it’s time for them to wind down and get ready for bed.

For advice on creating a great evening routine for your baby, visit our blog:

How to Help My Baby Sleep — The Perfect Evening Routine.

What Happens If You Can’t Reduce Startling?

Actually stopping your baby from startling isn’t actually possible, but if you’re even struggling to calm your baby down after they startle, or they seem to be waking up crying far too often, you might be feeling concerned. 

We’d recommend staying patient and as long as you’ve done what you can to reduce the potential triggers of startling, and care for your baby once they’re awake and crying, don’t worry too much about your child experiencing the Moro reflex. It’s just another natural part of baby development and growth. 


Final Word

It’s completely normal for babies to exhibit the startle reflex. If your baby cries when startled, just do your best to make them comfortable and calm them down, either with some of your favourite soothing techniques or by wrapping them up in a swaddle or swaddle transition garment.


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