If you’re subscribed to a pregnancy newsletter (like ours!) one of the highlights is seeing the progress that your little one is making each week.

Knowing that they’re currently growing little ears or that they’ve started to blink helps you to connect with the tiny human you’re waiting to welcome into the world.

As the pregnancy progresses, you’ll likely see familiar routines start to develop. Maybe it seems your little one is very active each evening as you’re cuddling on the couch with your partner. Or your surrogate might mention that she wakes up each morning to tiny kicks and flutters.

You may wonder whether this means your baby is sometimes asleep and sometimes awake. You may wonder what they’re aware of while inside the womb. We’ve checked out the research to give you answers to these questions and more.

Yes. In fact, as far as we can tell, babies spend the majority of their time in the womb sleeping. Between 38 and 40 weeks gestation they’re spending almost 95 percent of their time sleeping.

Less is known about sleep during early fetal development. Technology has limits, even now. Most of the studies on fetal sleep early in pregnancy rely on examining rapid eye movement, a feature of REM sleep. Sometime during the seventh month of fetal development the first rapid eye movements are observed.

Studies of sleep demonstrate that there are four stages: the first two are lighter sleep, while the second two represent deep, healing sleep.

In addition, there’s REM sleep, which begins about 90 minutes into a sleep cycle. This stage is characterized by a rise in breathing, blood pressure, and heart rate. The eyes move quickly and brain waves are similar to those of someone who is awake. This is the stage where you are likely to dream.

As mentioned, there are limits to what researchers can learn about fetal sleep, but based on what we understand about sleep in general, it is possible that babies are dreaming during REM stages. As to what they’re dreaming about, we can’t know for sure.

But some could argue that they must be dreaming about food, based on the intensity of those pregnancy cravings, right?

Researchers have used a variety of methods to study fetal sleep behaviors.

Researchers in a 2010 study tracked fetal heart rate and found that the results demonstrated regular sleep and waking patterns.

In a 2008 study, researchers used fetal electrocardiographic (FECG) recordings to compare the same subjects both in utero and as newborns. They tracked four states — quiet sleep, active sleep, quiet waking, and active waking. Each state was identified by eye movements, heart rate, and movement.

They found that there were similarities in the sleep patterns established in utero, but that newborns who had spent more fetal time sleeping showed more mature sleep patterns as newborns, meaning that they slept less than they had pre-birth.

That being said, don’t expect your little one to be a great sleeper just because they don’t wake you up all night during pregnancy. While newborns still tend to spend most of their time sleeping, they should be waking for feedings every few hours around the clock.

Researchers in a 2009 study turned their attention to fetal sheep to understand the earliest sleep patterns that are harder to study in human subjects. Brain activity in the fetal sheep showed patterns of behavior that suggested early, immature sleep cycles.

Sleep isn’t just about rest and dreaming, of course. A small 2018 study of premature infants showed that movement during REM sleep helps them to process their surroundings and sparks brain development.

Much of the research on sleep that’s available focuses on the effects of a lack of sleep, but what evidence we do have indicates that sleep is an important factor for brain development and overall health.

Your baby’s brain begins to develop as early as 1 week after conception. In the early weeks the brain, along with other important organs, is growing in size but is not well-defined. As the weeks move on it grows in both size and complexity.

Taste buds begin to develop in the first trimester. Flavors and smells from mom’s diet are present in amniotic fluid.

Movement begins long before you’re able to feel it (usually around 20 weeks). While you may not be aware of all movements, your fetus likely moves around 50 times or more in an hour. These movements don’t necessarily mean that they’re awake though — they move during both sleeping and waking cycles.

The structure of the middle ear develops in the second trimester. Around week 25 or 26, your baby may demonstrate signs that they recognize your voice.

So while your little one may spend most of their time in utero sleeping, much is happening at the same time. Even in their dozing state they are developing their senses and an awareness of their surroundings and preparing for their big debut.