Your Baby's Developing Senses and Sleep-Wake Cycle During Pregnancy

Babies are born with a complete sensory system, including sight, smell, taste, touch, and hearing. In the womb, babies spend most of their time sleeping, but when they are awake, they experience various sensations, such as hearing the muffled sounds of their gestational parent's heartbeat.

A fetus's senses start developing just a few weeks after conception, forming the basis of their understanding of themselves and the world around them as well as their attachment to you. Keep reading to learn what your baby is experiencing throughout every stage of your pregnancy.

What Do Babies Feel in the Womb?

Touch is the first sense your baby will develop, with receptors beginning to form as early as 8 weeks into pregnancy. As part of the somatosensory system, your baby's sense of touch is a key survival tool that will help them explore the world after they're born. These receptors are also crucial for their development in the uterus: By sensing various stimuli, the receptors help signal when it's time to develop the nervous system.

Although these touch receptors allow your baby to be more aware of their surroundings, they won't be able to sense and process certain feelings—such as pain—until much later in pregnancy. It will take until at least 24 weeks for a fetus to develop the neural connections and structures needed to sense these more complex sensations.

What they can do early on is to feel their own bodies and their surroundings in the uterus. They also can sense what happens when they move within the amniotic fluid. These sensations continue to evolve, eventually allowing the fetus to develop a sense or "map" of its body and some awareness of the environment around it.

How Do Babies Move in the Womb?

Around the ninth week of pregnancy, your baby starts making their first movements. Those movements are probably visible with an ultrasound, even though you won't feel them just yet. By 13 weeks, your baby may be able to put a thumb in their mouth (the sucking muscles aren't completely developed yet though).

Your baby's first muscle movements in the uterus are involuntary, but the first voluntary muscle movements occur around week 16. After this point, awake or asleep, they move 50 times or more each hour, flexing and extending their body, moving their head, face, and limbs, and exploring their warm, wet home by touch. A baby may touch their face, touch one hand to the other hand, clasp their feet, touch their foot to their leg, or their hand to the umbilical cord. By week 37, your baby has developed enough coordination so that they can grasp with their fingers.

Along with these common movements, babies perform some strange behaviors, including licking the uterine wall and "walking" around the womb by pushing off with their feet. Fetuses also react with motion to their parent's actions. For instance, ultrasounds have shown a fetus bouncing up and down when the parent laughs. Watching this on the screen, parents-to-be often laugh harder, and the fetus starts moving up and down even faster!

Second or third children may have more stretching room in the uterus than first babies because the uterus is bigger and the umbilical cord is longer after a first pregnancy. These children usually get more motor experience in utero and tend to be more active infants.

How does a baby's movements in the uterus feel to a pregnant person? Quickening, as this feeling is called, is typically first felt around weeks 16 to 20 of pregnancy. It may feel like fluttering, bubbling, or tiny pulses in the belly. By week 29, you should be feeling your baby move at least 10 times an hour. The movements will likely feel stronger over time as your baby grows. You may even feel your baby somersault, kick, or hiccup in your uterus.

Do Babies Sleep in the Womb?

Expecting parents often wonder if babies sleep in the womb. They definitely do! Just like newborns, growing babies spend most of their time sleeping. In fact, throughout much of the pregnancy, your baby sleeps 90% to 95% of the day. Some of these hours are spent in deep sleep, some in REM sleep, and some in an indeterminate state—a result of their immature brain. During REM sleep, their eyes move back and forth just like an adult's eyes.

Some scientists even believe that fetuses dream while they're sleeping. Just like babies after birth, they probably dream about what they know: the sensations they feel in the womb.

Interestingly, the sleep patterns of the pregnant person have been shown to affect the sleep of their growing baby. This impact extends beyond the present moment into childhood, making it all the more important for pregnant people to get adequate rest.

What Do Babies Hear in the Womb?

Your baby may be able to hear your heartbeat (and other sounds in your body) as early as 18 weeks, according to the American Academy of Pediatrics (AAP). By 27 to 29 weeks, they'll start hearing things outside of your body, such as your voice. They'll also recognize sounds they hear regularly, such as music and specific voices, and those familiar sounds may bring them comfort after they're born.

Newborns can not only distinguish their parent's voice from a stranger's but would rather hear their parent's voice, especially the way it sounds filtered through amniotic fluid rather than through air. They also prefer to hear their parent speaking in their native language than to hear them or someone else speaking in an unfamiliar language. Of course, babies are reacting to the overall sound of voices and stories, not your actual words.

Can Babies Taste in the Womb?

While taste buds start developing around 8 weeks, your baby won't utilize this sense until around 15 weeks. By this point, they'll be swallowing amniotic fluid, which contains molecules from your meals. They'll be able to "taste" some stronger flavors, such as spices and garlic. (Because their sense of smell isn't fully developed, fetuses won't experience flavors as strongly as you do). When they're born, they'll have about 10,000 taste buds—even more than adults.

Some experts say that your diet during pregnancy will influence your baby's eating habits in the future—so make sure you're eating plenty of healthy, nutrient-rich foods while expecting! And here's an interesting fact: Babies generally prefer sweet flavors, which makes your breast milk more appealing to them.

Can Babies See in the Womb?

Your baby's eyes will start developing as tiny outgrowths of the brain at 6 weeks, with the eyelids forming about a month later. These will remain closed until the end of the second trimester, around 27 weeks. By 31 weeks, they should be able to detect and respond to bright lights. You may even sense some movement if you shine a flashlight at your belly! In the final weeks of pregnancy, your baby should be able to focus on large objects and track movements. Their eyes will continue to develop after birth.

What Do Babies Smell in the Womb?

Your baby's sense of smell is one of the first senses to develop, with their olfactory receptors forming as early as 8 weeks. They'll start using their sense of smell in the womb while breathing and swallowing amniotic fluid, becoming familiar with its scent—and yours. That's because its smell is similar to the smell of your breast milk.

By the time they're born, your baby's sense of smell will be highly developed. They'll easily recognize you from the scents they detected inside the womb, and that's why they'll be drawn to you—and deeply comforted by your presence.