There are endless amazing things about conception, pregnancy, and the development of what will soon be a fully fledged baby. Over the course of 9 months, what can only be described as biological miracles (with plenty of scientific evidence and backing behind them) happen inside the uterus. From a cluster of cells grows a humanly recognisable baby. Go human body!
The cluster of cells that happen when the female ova meets the male sperm undergoes a truly remarkable transformation, in both growth and development. Over the course of the weeks and the months, those cell buds sprout into little limbs and organs that grow and develop. Soon enough, the ultrasound shows little waving arms and little kicking legs. There are little eyes forming and little mouths learning to suck in the air.
Amongst the things that develop in the womb are the ears. These super important organs, often taken for granted, have some impressive development taking place. It takes a while after conception for the cell buds that make the ears to take shape. Around 16 weeks is when they will stand out from the side of the head. After 18 weeks, the fun and games really begin for the ears. Find out just what the ears can hear and what they’re up to during pregnancy.
By 6 weeks after conception, the cells inside the baby’s body are rearranging themselves into position to form organs. It is at the 6 week mark that the ear bud cells are in place, ready to embrace the unique tissue that makes them ears. By week 9, there are teeny tiny indents on the side of the head, marking the place for ears to come.
The ear structures are in place by 16 weeks, and at 18 weeks some sounds are starting to filter in. These sounds might surprise the baby at first, maybe you’ll feel a kick of shock or protest of music playing too loudly as time progresses. At first, the sounds can’t be distinguished by the baby’s ears. They are just muffled noises with no meaning. This does change over time!
Although the baby’s ears can hear noise and sounds by 18 weeks, it takes until about 24 weeks for the baby to really realise what’s going on. Before the 24 week mark, the noises have had little to no significance registering in those ears.
There has been a lot of investigating done by science and doctor teams around the world to see if babies really do respond to noises on the outside of the womb. It has been proven that after 24 weeks, babies will start to turn their little head in utero when they hear a familiar sound. This means that they actually start to recognise things like voices, music, and sounds. And the brain processes them and remembers them. Such amazing stuff going on already in the uterus!
There are many ways that mom and bubs are connected during the pregnancy journey. Beyond the physiological connection of the placenta and the whole sharing the uterus thing, there is a deep emotional connection that is present at the moment of delivery. The feeling shared between mom and baby, the instant bond, and the immediate sense of love very much develops in the womb with the baby.
Perhaps contributing to this love and bond is the fact that the baby can literally hear mom’s heartbeat. After around 18-20 weeks, the sound of the beating heart is audible to the baby. This means that the baby can hear when the heart beats faster and knows when mom is excited or relaxed. What an amazing insight that little growing baby has to their mother, through their ears.
Standing up? Sitting down? Rolling over? If an expectant mom does any of these types of movements, the baby can hear it from inside the womb! Babies' ears become quite sensitive to body movements after 24 or so weeks. This includes things like muscles moving or bones cracking.
Therefore, if you are having a particularly creaky day and really feeling those aches and pains in the joints, little bubs is going to hear about it. It you are working out, bubs is going to hear the muscles and bones moving around. And yeah, nothing is personal when it comes to a baby hearing what’s going on from the inside. Even body movements associated with using the toilet, for ones or twos, can be heard from those little developing ears. Oh, and if you are getting busy in the bedroom, that can be heard too!
The cravings that come with pregnancy are common knowledge. They are bizarre, they are random, and they can hit at any time. Many people do notice the additional eating and the odd combination of food that starts entering a pregnant woman’s diet, but how many people can hear it?
With pregnancy comes the notion that you are eating for two. This is literal in a sense, since the nutrients you put into your body is broken down and shared between your bloodstream and the baby’s, via the placenta. Couple this with the hormonal changes and emotional rollercoaster that is pregnancy, hunger becomes inevitable and is enhanced with the cravings. So when the tummy is rumbling and demanded some pickles with potato chips, the baby can hear it! The movement and noise of the stomach when hungry echoes around the baby’s developing ears.
Breathing can become harder during pregnancy for many reasons. First of all, there are mood swings and emotions that can cause mild moments of panic. Normal. Secondly, there are physiological changes going on inside the body. Biology gets weird here.
As the uterus grows with pregnancy, it pushes on the diaphragm and creates additional pressure. As a result, the heart and lungs have to shift around slightly. As the lungs become compressed thanks to the uterus, breathing becomes more difficult. Many pregnant women experience shortness of breath more easily, as if they’ve run way too much.
So as the baby grows bigger and the ears develop more, the two go hand in hand. Mom’s breaths become more and more enhanced, and the baby can hear the air coming in and out even louder.
Ok, this one gets a little weird. It is on a pretty too much information level. Not many people think too closely about blood. Sure, we all know it’s important and necessary and is literally our life support. It makes its way through the veins as it is pumped from the heart. During pregnancy, the volume of blood pumped from the heart actually increases between 20%-50% over the time. This is obviously so that the baby can receive the life sustaining blood through the umbilical cord and placenta.
However, not only does bubs receive this blood directly into the veins, but it can also hear the blood being pumped around. Blood moves through veins and vessels that are all around the body, including around the stomach and uterine area. Therefore, there are veins that are located right near the baby’s ears. So yeah, bubs can hear the flow of blood. How weird!
After 24 or 25 weeks of development in the womb, the baby’s ears start picking up on sounds that are constantly surrounding them. After all, these little ears are exposed to everything that mom is doing. This includes music, talking, the start of a car engine, and most importantly, the sound of mom’s voice.
The more a sound is repeated, the more it is recognised. Therefore, the more the baby hears a sound over and over again, the more it is processed by the brain and stored in the growing memory bank. There is much evidence to suggest that babies can recognise their mom and/or dad and/or the people who talk to expectant mom the most. This is super cool to think that once the baby comes out of the womb, it is already going to know the sound of your voice. Talk about finally putting a face to the voice!
Going on from the point mentioned above, babies do in fact start to recognise voices. Obviously, expectant mom’s voice is going to be the most obvious (especially when she starts talking to herself from all the pregnancy fatigue and delusions!). Also, the voices of other significant people, such as mom’s partner, family, and friends, start to be registered in bub’s growing ears and brain from around 25 weeks.
When the heartrate of the baby is being monitored, in an ultrasound for example, there are many cases where the heart rate will rise and bounce around once mom or someone else significant to baby starts talking. This is because the baby recognizing voices and being excited to hear it. Don’t be too disappointed if this doesn’t happen at first. Sometimes it takes more than 30 weeks to really register the voice. And sometimes the baby might be sleeping when you’re talking so they won’t even hear you!
There is much debate over playing classical musical such as Beethoven makes babies smarter. The evidence on this one is like thin ice, but of course, music never hurt anyone. While it may not make the baby a genius at birth, playing music definitely does register with babies.
As a mom, you may have a greater impression on your baby’s future music tastes depending on what you play in the womb. Babies will start to recognise tunes and beats as they are further along their gestational journey. Their heart rate will rise and fall depending on what type of music you’re playing. Of course, don’t take your baby to a rave in the womb - the developing ears aren’t ready for that just yet! By all means, playing music, classical or otherwise, is something the baby will hear and appreciate.
One thing that any parent can do for their children that will mean a lifetime of benefits is reading. This simple act means so much for so many aspects of development, literally at any stage of the lifespan. Reading aloud to newborns, babies, toddlers, and children as they grow up is one of the best gifts any parent can give. And it turns out that reading aloud is appreciated even in the womb.
When the ears kick into gear and the baby can hear sounds after 24 or so weeks, they become more attuned to the noises going on around them. While they won’t be able to distinguish and understand the words of a story book, they will be tuning in for some story time. This is best done later in the pregnancy, towards the end of the third trimester. Reading aloud is a great bonding experience while bubs is still in the womb, and also a great way to practice that intonation you’ll need to read endless stories after birth!
So we’ve established that babies can in fact hear things from inside the womb. They can eventually recognises noises, sounds, music, and even voices. But what exactly does this sound like to a baby. After all, they are inside a womb. And that womb is surrounded by amniotic fluid, a sac like bubble, and mom’s exterior belly.
Of course, a baby in utero doesn’t hear in the same way that we hear sounds. They don’t distinguish words and letters and lyrics of a song. Rather, it is like how we can still hear noises around us under water, or with big muffler earphones on to combat a snowy day. The sounds are certainly muffled, but they are still audible. This is why the baby won’t recognise words as such, but will recognize and respond to different volumes and tones.
It makes total sense, even for humans with fully functioning ears, that the louder the sound, the better it is heard. Of course, if someone is mid conversation and they suddenly drop their voice to a whisper, it is going to be harder for the second party to hear them well. The volume of sounds affects how the baby can hear them in the womb, as well.
Given that babies are only hearing a muffled version of the noises or words being said on the outside of the womb, the volume is important. So if you’re having a quiet walk in the park, the baby won’t hear the chirping of the birds or swishing of the leaves. However, if you’re in the car listening to music really loud, bubs is going to be rocking along with that.
Since babies can start registering sounds by 24 weeks in the womb, many sounds become more and more familiar over the course of pregnancy. Some sounds that are heard on a daily basis, such as mom’s voice or the dog barking, therefore become really familiar.
These sounds stay in the baby’s brain and memory that have developed in the womb. They literally leave an impression there. Hence, when the baby comes out of the womb, after all the screaming and sweating and pushing of delivery, there are some sounds that are going to register. Of course, mom’s voice is one of these. This is part of the instant bond that mom and bubs share at delivery. Other sounds, such as the car engine, the door opening, the dog barking hello, won’t startle the baby as much since they are already familiar.
Sources: Whattoexpect.com, Healthline.com, Parents.com