How Baby’s Hearing Develops
A baby’s hearing develops remarkably early in pregnancy. Consequently, your little one begins soaking up information from the outside world far earlier than you may have expected.
Six Weeks
Beginning at around six weeks’ gestation, the cells inside of the fetus’s developing head are already starting to arrange themselves into unique tissues that will eventually be the brain, face, ears, eyes, and nose. Even though you cannot see the ears during an ultrasound, the intricate arrangement of tubes that make up the inner ears is starting to develop.
Nine Weeks
At nine weeks, there will be small indentations on the sides of the baby’s neck that represent future ears. Even though they are not in the right place, they will gradually move into the correct location. Your baby’s ears continue to develop throughout the first and second trimester. For instance, the inner ear connects with neurons in the brain that are responsible for processing sounds. Meanwhile, the tiny bones in the middle ear, which sense the vibration of sound waves, also begin to form.
16 Weeks
By around 16 weeks of pregnancy, it’s very likely that structures in the ears are formed enough that your baby may be able to start detecting some sounds. In fact, some of the first sounds a baby hears include the beat of your heart, the gurgle in your stomach, and the sound of air entering and leaving your lungs. As hearing continues to develop, your baby will begin to hear more and more of the world outside of the womb.
24 Weeks
By 24 weeks, the ears are fully developed, and research has shown that many babies will turn their heads in response to voices and other noises. There is amniotic fluid surrounding your baby, as well as all the layers of your body. So the sounds heard in utero are muffled because there is no air to carry the sound. Recordings taken in the uterus reveal that noises outside the womb are muted by about half.
What Baby Hears Most
Not surprisingly, the clearest voice your baby can hear is yours. Most of the sounds your baby hears are transmitted through the air and then through your uterus. By contrast, your voice reverberates through your body and your bones, which amplifies the sound. If you sing a song with your mouth covered, it’s likely that you will hear the tune but not the lyrics. The louder the sound, the more likely your baby will be able to hear it—especially things like a dog barking, a train passing close by, a siren blaring, and so on. Your baby’s hearing will not be damaged by these sounds. Research has shown that a fetus’s heart rate increases after hearing its mother’s voice, meaning your baby is more alert when you’re speaking. As a result, it is a great idea to talk to your growing baby. You also can read books and sing lullabies. In fact, research indicates that babies hear what their moms say and recognize these words after birth. Interestingly, the study also found that babies can detect subtle changes and process complex information. During the study, researchers at the University of Helsinki in Finland looked at 33 expectant mothers and examined their babies after birth. While pregnant, 17 of the mothers listened to a CD at a high volume with made-up words said different ways and with different pitches from week 29 to birth. Overall, the moms and their babies heard the nonsense words about 50 to 71 times. Then, following their births, the researchers tested all 33 babies for normal hearing, and then performed an EEG brain scan to see how the newborns responded to the made-up words. For the babies that heard the nonsense words while in utero, their brain activity picked up when those words were played. The babies who did not hear the words did not react much. The researchers concluded that an unborn baby can learn and remember just as well as a newborn. Consequently, they believe it may be worthwhile to expose babies to more sounds before they are born.
Loud Sounds and Developing Babies
Most moms are concerned that very loud sounds will damage their baby’s hearing such as a loud concert or a noisy night out with friends. In most cases, these one-time instances will not impact your baby’s hearing. While the effects of prolonged noise on hearing loss are not well-known, noise does have the possibility to cause some developmental damage or hearing loss in a growing baby when it’s loud, prolonged, and repeated. For instance, working in a noisy factory for eight or more hours per day might be enough noise to impact a baby’s hearing to some degree.
Bonding with Your Bump
You may have heard that playing classical music while you’re pregnant will boost IQ and build a solid foundation for your baby’s educational future. There is no research to support these theories. Still, there’s no harm in playing some soft music now and then for your developing baby, especially if you enjoy it and it helps you relax. You also can read books and sing lullabies. All of these things not only allow you and your partner to stimulate and support your growing baby’s hearing, but also allow you both to bond with your unborn baby.
Hearing in Infancy
Statistics indicate that about one to three of every 1,000 babies will be born with hearing loss. While there are any number of reasons for this, some of the more common causes include premature delivery, high bilirubin numbers, certain medications, trauma, and family history. After your baby is born, you can monitor their hearing by being aware of what to expect in terms of developmental milestones. Understanding what is considered normal and what is not will help you know when to talk with your baby’s pediatrician.
Birth to three months: Your baby should react to loud noises, recognize your voice, coo, calm down when you talk, and have different types of cries for different needs. Four to six months: Your baby should track you, notice noise-making toys, respond to changes in your tone of voice, notice music, and laugh. Seven to 12 months: Your baby should turn in the direction of sounds, listen when you are talking, understand a few words, babble, and communicate by waving or holding up their arms.
A Word from Verywell
Knowing that your baby can hear what you say—or sing— during pregnancy should be encouraging. Talking to your growing baby is actually beneficial for your child. So, keep chatting away. You’re helping support your growing baby’s hearing development.
