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Why Does My Baby’s Leg Shake?

One day you glance over and see your baby’s leg (or body part) shaking? That’s an odd thing to witness as a parent. Most of us might assume it is a seizure of some form – when it’s a harmless cause of the shaking.

Most of the time shaking in babies is completely harmless, and they grow out of it in time. That’s not to say there haven’t been infants having a seizure, so it’s important to know when to be concerned.

You want to be able to recognize if there is a true cause to call an ambulance. 

While there are plenty of reasons your baby’s leg or body part can be shaking due to causes that are natural for some growing babies like an immature nervous system or a bit of caffeine in mom’s breast milk.

The Nervous System Is Reacting

Your baby’s brain tells the rest of the body when to go, what to do, and how to respond to outside activities. If the brain tells your baby that it’s time to move the leg, but the nervous system is not fully developed, the leg can twitch or jerk harmlessly. 

This is sort of like a practice run for the nervous system. It’s simply a matter of time before your infant’s nervous system matures and the brain to limb connection will happen without any shaking. 

Any limb or body part can be affected by an immature nervous system, so if you see your baby shaking in multiple locations or random places, it’s even more of a sign of an immature nervous system.

Your baby probably won’t even notice it happening and continue interacting as usual.

Mucous Myoclonus While Asleep

Correct me if I’m wrong, but we adults have all experienced times where we drifted off to sleep only to be woken abruptly feeling like we’ve been forced awake.

sleeping baby

This happens either due to reflex response within the body or an outside noise interrupted their sleep causing them to shake and fully wake up again.

Though they will still be sleepy once they do wake up again, they’ll probably drift right back to sleep after doing this. Sleep Myoclonus has another name: nocturnal myoclonus. 

Daily activities that are happening around your soon to be asleep infant can also cause this kind of reaction, like if you turn on or off a light. It’s a non-intentional reaction in your baby while drifting off to sleep.

A Startle Reflex Called Moro

Moro Reflex is when an infant suddenly reacts sprawling out their arms or legs. This is caused when outside factors surprise your baby. They are fully alert when Moro happens to them, it’s not something they do on purpose. 

Infants who have Moro will outgrow it as their reflexes become more controlled. Until then, you might see your baby involuntarily arch their back for a few seconds, spread their hands and fingers, while reaching out as far as possible with their arms and legs.

The baby looks slightly startled, and like they need a little hug after doing this. Some babies’ eyes widen as they arch back as this happens too.

This occurrence is nothing you have to worry about as a new parent and will see this most often between 3 – 6 months of age.

Getting A Diaper Changed

Who likes diaper changes? Not your baby. Some might even shake when you start to change their diaper. Some babies tell their parents how much they dislike having their diaper changed by shaking while they are having it done. 

baby diaper change

This happens to a lot more parents than you’d think. One mother commented on Community Baby Center that her baby would do this at 3 years old while having a diaper changed.

She even went as far as to ask teachers if anything happened to her son at preschool. Reassured nothing had, then she connected with other mothers who also had babies who would do this during every single diaper change.

If you’re experiencing this with your infant baby, they might just shake and cry while it happens. Once they become a toddler, they would be more outspoken about it and involve a panic like a scream or a holler while shaking.

Your Baby Is Ready To Eat

Food is the culprit. Well, your baby needing it right then is.

If you find your baby is shaking after they’ve already been crying for food, it’s probably due to your baby needing some food, and not being able to hold back the intense feelings happening within their body. 

Sometimes, as parents, we have to get through the last block of the car ride until we can pull our baby out and feed them. Little babies don’t get this, and they might freak out when they’ve run out of patience.

They are overwhelmed with emotions, hunger pains, and not getting their way, causing their bodies to twitch, shake, or tremble. 

If this happens, soothe your baby until they are completely calmed down, give them the food they are stressing over as soon as possible. Keeping a bottle handy in the car will keep this from happening on road trips and long drives.

Another important aspect of this type of shaking in babies is that low blood sugar contributes to it. That’s not a good feeling especially as a small human who has to keep up with growing physically at a rapid rate. 

If this happens even after feeding your child, or often soon after they’ve already had a meal, mention it to your pediatrician to get an informed opinion.

Reasons To Be Concerned When Your Baby Is Shaking

Seizures are every parent’s worst nightmare. Whenever they watch their babies fall down or bump their heads, a breath of air is held in extra long until their baby starts to cry or gets up again.

Rightfully so, a seizure can be harmless like from heat exhaustion too.

Even though babies might be okay having a seizure once or twice, over time there would be harmful effects within the body if seizures and spasms happen often. 

baby and pedia

It’s a good measure to have a baby looked over by a doctor for outside causes or brain damage, every time a seizure takes place until diagnosed.

Pediatricians will walk you through the signs and symptoms of a seizure, how to handle one best possible, and what possible meds are used for frequent seizures in small kids. 

But, here are the most obvious signs to look for that caregivers can recognize in babies experiencing a seizure – harmful or harmless.

  • The episodes repeat in the same manner each time, with indicating symptoms that are identical each time.
  • If the baby is alert, and no change in the environment has happened to cause the reaction. The posture of the baby has not changed at the time of shaking.
  • Symmetric movements are happening, in a rhythmic way. If you notice that there is a certain pattern or vibration to the strange movements then this indicates seizure-like movements in a small child. Their hands, feet, arms will be shaking simultaneously in the same manner.
  • If you’ve grabbed your baby’s arms or legs that are shaking – with no sign of them calming down it is probably a seizure. With shaking that is not a seizure happens, it stops when you grab the body part shaking. When a true seizure is happening it does not stop even with your touch.
  • All growth and development milestones are otherwise healthy and on track. Babies who have seizures tend to have no other issues aside from the seizing episodes.
  • Behaviors that are unlike any other children in that age range are happening, then it could indicate a seizure. Do a bit of research if your unsure, and check if the behaviors are usually experienced within the age range.

Other Parents Share Their Experience With Their Own Babies

You aren’t alone in the bit of concern you might be experiencing due to your baby’s random shaking. Many other parents have gotten through harmful baby leg shakes to full-blown seizures here’s what they saw, heard, and went through initially.

Some mothers suggested that it was acid reflux. Others knew intuitively their baby would grow out of it, and some mothers were advised to seek assistance from the pediatrician to truly pinpoint the cause of the shaking.

Another parent noted that she had to take her baby’s temperature rectally the previous week, and since then the baby would shake while being put on the changing table from the situation.

The next case for the very concerned mother of a newly walking boy stated that her son’s leg would twitch quite noticeably, even while he was walking.

It would affect his walking to the point of him sitting down each time it would happen. At around 12 months of age, her son grew out of it, and the pediatrician said it was perfectly normal.

It was his body’s way of “working out the nervous system twitches” a perfectly normal part of his growth.

mother and baby


Most shaking that your baby is having will end up being harmless, and not long-term. Babies go through various ages, stages, and physical changes too.

Most babies who shake, twitch, or jerk randomly can be explained by connecting with other parents who have experienced this as well.

If you’re feeling uncertain about your babies shaking or it happens often it’s a good idea to see the pediatrician regarding the newfound shaking.

Remember to keep an eye out for symptoms of seizures. You can even start a journal for your babies shaking especially if it’s happening often. This would be helpful to your child’s pediatrician too if needed.

Remember to remain calm and reflect back on the research you’ve done here to better pinpoint why and be there fully for your baby throughout the episodes.

There is plenty of support out there for new parents experiencing new events with their babies. After all, there’s no one size fits all handbook that tells you what your child goes through or why.

Most shaking in a baby’s legs, limbs, or through spontaneous reactions will be outgrown eventually as their nervous system develops too.