When Do Babies Start Dreaming? Most Likely in the Womb.

Science can’t determine what images a baby’s brain conjures during sleep and the babies aren’t talking.

Watching a baby sleep is one of the greatest pleasures of parenthood. There is so much joy in watching them breathe softly while their peaceful angelic faces shift from sleep sucking to tiny sleep smiles. But do those facial movements mean babies have started dreaming? It’s hard to say. Because even with sophisticated brain scanning equipment, it’s impossible to say exactly when babies start dreaming because we can’t possibly see what they see inside their heads while they sleep. That said, there are clues as to when baby dreams might start. And it’s possible they might begin far earlier than most parents would assume.

The Case for the Dreaming Fetus

Science can’t determine what images a baby’s brain conjures during sleep and the babies aren’t telling us themselves. However, researchers can observe biological processes that correlate with dreaming, chief among them being rapid eye movements. Rapid eye movements (REM) are the primary characteristic of REM sleep, a stage in the sleep cycle when humans are most likely to dream.

“The dreaming state is just REM sleep,” says nurse practitioner Maile Moore of The Boston Children’s Hospital Sleep Center. But having REM sleep and knowing you’re dreaming aren’t necessarily the same. “Even for adults, we have REM sleep but we’re not conscious we’re dreaming and we don’t always remember our dreams.”

It’s clear that, based on real-time fetal ultrasounds, babies in utero experience typical sleep cycles that include periods of both REM sleep and non-REM sleep. One of the first studies to observe fetal REM was published in the journal Early Human Development in 1992 by Japanese researchers. Scientists found that REM movement was detectable between 28 and 30 weeks of gestation and that the periods of REM sleep increased as the pregnancy progressed.

“REM sleep is restorative for the brain,” Moore says. “It’s good for memory consolidation.”

Does that mean that fetuses are dreaming? And what good would it do them? Well, we know that REM is incredibly important for learning, according to Moore. “REM sleep is restorative for the brain,” she says. “It’s good for memory consolidation.”

We also know that the womb is an incredibly lively place and that fetal sensory abilities like sight, smell, taste, and touch are fairly well developed by the thirst trimester of pregnancy. So it’s possible, but completely speculative, that a fetus can dream during REM sleep and that those dreams might incorporate womb experiences like parent voices and tactile sensations and help code them into the brain and give newborns a cognitive head start.

How Baby’s Might Dream

Newborn sleep cycles can be as short as 45-minutes with periods of wakefulness in between. Even though the cycles are short they still contain periods of REM sleep and deeper non-REM sleep. As babies grow the sleep cycles get longer until they have more typical 90-minutes cycles with periods of wakefulness in between.

REM sleep cycles in babies are just as crucial for brain development as they were in the womb. But they are also far cuter to observe. Parents might notice this REM sleep while watching a baby sleep — characterized by the eyes seeming to dart back and forth and up and down behind the eyelids. Along with these eye movements, parents might see their baby make sucking movements or even smile. These may be indications that an infant is dreaming. They do have plenty to dream about with the sheer amount of input they have to receive and process when they’re awake. It’s possible that babies dream of their parent’s faces and voices. It’s possible that they dream of the environments in which they’ve spent time during the day. It’s even possible that they dream of breastfeeding. Alas, we’ll never know because they can’t tell us.

Importantly, Moore says that REM sleep isn’t particularly deep. “When you’re in REM sleep you can easily wake up out of it.” So if you’re going to watch your baby dream, do so quietly.

Until they can talk, a kid’s dreams will likely remain a mystery for parents. So it’s a guessing game until children are able to string enough words together to describe their nightly visions.