Why does my baby cry in his/her sleep?
I went to a mom group this week and heard a new mom say,
“Oh yeah, she has started to cry in her sleep. It’s kind of creepy.”
I couldn’t help but chuckle, because yes, it can feel unsettling the first time you hear it. But it also tugged at my heart. So often, we miss these moments for what they really are: communication. And when we misunderstand them, we can start to worry that something is wrong, when in reality something very normal is happening.
Let’s talk about why babies cry in their sleep, what it can mean, and how to respond in a way that supports your baby’s developing nervous system.
Birth Is a Massive Transition for Both of You
The process of birth is usually long and intense. It requires instinctual but exerted effort from both mom and baby. Babies release hormones to signal readiness. They push, twist, and work their way through the birth canal.
Birth is not just a physical experience. It is emotional, neurological, and relational. Everything changes in an instant.
There is now an extension of you, but all your baby has ever known is you.
They do not yet understand where they end and you begin. Developmentally, babies are born without a fully formed sense of self. As neuroscientist Dr. Greer Kirshenbaum explains, infants are wired for co regulation. Their nervous systems rely on a caregiver’s presence to feel safe and organized.
The world does not feel right unless they are close to you.
This is why we see such a strong emphasis on skin to skin immediately after birth, room sharing and proximity at night, and the biological draw toward co sleeping across cultures.
For most of human history, keeping babies close was never questioned. It was survival.
Even Beautiful Births Can Carry Trauma
All that to say, huge transitions have happened.
No matter how peaceful, empowering, fast, long, medicalized, or redemptive your birth experience was, there is still a very real sense of stress and disruption experienced by both mom and baby.
Trauma does not always mean something went wrong.
Trauma simply means the nervous system was overwhelmed.
Both bodies carry memories of pressure, separation, sensory overload, and sudden changes in temperature, light, sound, and gravity.
There is a lot to process.
So What Does This Have to Do With Crying in Sleep?
Here is the connection.
Crying, and early vocalizations since newborns do not produce tears right away, is one of the primary ways the brain processes experiences.
As Rest Play Grow teaches, emotions are not something to be worked through cognitively in infancy. They are felt and discharged through the body.
Crying helps the nervous system say, “Something big happened, and I need to adapt.”
It is how the brain integrates change.
And sleep is when integration happens.
During sleep, the brain stores memories, both implicit felt experiences and explicit events. So as your baby sleeps, it makes sense that their nervous system may replay parts of the birth or early transitions as those memories are being organized.
This can sound like whimpering, fussing, crying out, sudden brief screams, or vocalizations that sound emotional but do not fully wake them.
Sometimes the cries sound distressed.
Sometimes they sound almost content.
The tone can reflect how your baby experienced the event emotionally, not whether anything is wrong now.
Other Common Reasons Babies Cry in Their Sleep
While emotional processing is a big piece, it is not the only one. Other common contributors include:
1. Immature Sleep Cycles
Babies spend much more time in active REM like sleep, which includes movement, noise, and facial expressions. Crying can happen between sleep cycles without full waking.
2. Digestive Discomfort
Food sensitivities, reacting to broken proteins in breastmilk or formula, gas, reflux, or gut immaturity, and gut dysbiosis can all play a role. This can range from grunting to screaming.
The nervous system and gut are deeply connected, so discomfort often shows up more clearly during sleep.
3. Overtiredness or Sensory Overload
Paradoxically, babies who are too tired often cry more in their sleep due to elevated cortisol levels.
4. Separation Awareness
As babies move through lighter sleep, they may briefly notice the absence of a caregiver and vocalize before resettling. This is especially common in the early months when proximity equals safety.
What Should You Do When Your Baby Cries in Their Sleep?
This is where reassurance matters most.
A baby’s cry can mean a thousand different things. But it does not automatically mean something is wrong.
What is always true is that your baby is communicating, your baby’s nervous system is developing, and you are the expert on your baby.
Often, the most supportive response is gentle touch, your voice, bringing them closer, or allowing the moment to pass without rushing to fix it.
Crying during sleep is a shared experience reported by many parents, especially in the newborn and infant months.
It is not a sign of bad sleep.
It is not a sign you are doing something wrong.
And it is not something that needs to be trained away.
If your baby cries in their sleep, take a breath.
Their brain is growing.
Their body is adapting.
Their nervous system is learning the world.
And with your presence, they are learning that the world is safe, even while they rest.
If you are feeling unsure, overwhelmed, or want support understanding your baby’s cues, that is exactly what Sleepy Starts is here for.
