Baby Sleep Patterns: Why Does My Newborn Move During Sleep?

By: Jenn Kelner, CPA, CA

Certified Child Sleep Consultant



Baby Sleep Patterns: Why Does My Newborn Move During Sleep?

Karen from Brownsville, Texas asks:

Q: I am a new Mom who was shocked to learn that my newborn has such vivid dreams! Her facial expressions change a lot from moment to moment. Why does she do that?

I also received a similar question from Sherry-Ann in Ohio:

Q: I have been teaching my child sign language and I have peeked at my one year old daughter at night and found her signing in her sleep! Milk, more etc. Am I working her too hard? Is this affecting her REM? I find it adorable but I am just wondering!

You wake up in the middle of the night to your child making noises or even fussing a little, only to discover that they are still fast asleep. Sometimes they may even be moving their arms and legs or smiling. Why does this happen?

To better understand why these babies are moving while they sleep, let’s first talk about what happens when we sleep. Sleep is divided into 2 distinct states: REM sleep, or “rapid-eye-movement” sleep, and non-REM sleep. After the first several months of life, non-REM sleep is then further divided into 4 stages. When we are in non-REM sleep, we dream very little and our bodies lie still with a steady heartbeat and breathing pattern. When we are in REM sleep, our heart rate and breathing becomes irregular and our brain function increases. This is where we do most of our dreaming. Although our brain function increases, our bodies becomes very relaxed and the nerve signals that usually pass down through the spinal cord and out to the muscles are blocked. This reduces the likelihood of us acting out our dreams. Throughout the night, we cycle through periods of non-REM and REM sleep, with the occasional waking in between. An adult sleep cycle lasts about 90 minutes and we spend about 20% of our total sleep in REM sleep.


Infants and babies go through cycles of 2 distinct sleep states as well: active sleep and quiet sleep. A baby’s sleep cycle is shorter than an adult’s, usually lasting about 50 minutes, and they spend about 50% of their sleep in active sleep. When they are in active sleep, the nerve signals are not fully blocked because the inhibitory system hasn’t fully developed yet. This means that more impulses get through to the muscles, often resulting in baby twitching, moving their limbs, smiling or making sounds. The inhibitory system fully develops around the same time baby learns to crawl or walk, so baby stays safely in place while sleeping.

Researchers suspect that some of the muscle twitching during active sleep corresponds to their dreams. This would seem true since Sherry-Ann’s baby was doing sign language in her sleep! Some researchers also believe that recent memories are transferred into long term storage during REM dreaming.

While it might seem strange or even alarming when your baby is moving in their sleep, there is a good reason for it. If you suspect that your baby’s movements are out of the ordinary, it’s always a good idea to check with your pediatrician.

Ferber, Richard, M.D. (2006). Solve Your Child’s Sleep Problems. New York: Fireside.