24th Week Baby Development: Hearing, Key Tests, and Gestational Diabetes

We are approaching a critical stage in pregnancy. In a very short time, the baby will be able to survive. This means that when born, our baby will have the ability to survive despite being born early, and this will be made possible thanks to the development of vital organs such as the lungs, brain, and especially the auditory system.

At this stage, the development of the senses is progressing rapidly, with hearing taking the forefront. The inner, middle, and outer ears are almost fully formed, and the baby is not only able to perceive sounds but is also beginning to respond to them, distinguish rhythms, and recognize the mother's voice.

How Does the Baby Look at 24 Weeks?

The baby is continuously gaining weight. It is now about 21 centimeters long from head to hips and weighs approximately 600 grams, but these values may vary slightly from baby to baby, and this is not a cause for concern.

In the lungs, the basic units where gas exchange will occur, future alveoli begin to develop. The lungs are not yet ready to breathe air, but they are at a critical stage of maturation, and the baby is training the muscles it will need by making rhythmic breathing movements while in the womb.

The baby's inner ear is in the final development stage and has started to hear. The structures of the middle ear (hammer, anvil, and stirrup) and the inner ear (cochlea and semicircular canals) work together to perceive sounds and transmit them to the brain. If you have talked to it, that's great; but if you haven't yet, this is a perfect time to start doing so consciously.

Thinking about its name is a good idea. By repeating its name, singing to it, or reading stories, it is important to establish a connection and realize that it is an individual growing in our belly, with its own personality and communication style.

Almost all sensory organs (hearing, smell, taste buds, and touch nerves) are functioning. It can now open and close its eyes, but its vision is not yet mature. Hearing and touch are now great tools for it to explore its inner world.

The baby is starting to interact, explore, and learn. It moves purposefully, responds to specific sound and tactile stimuli, and is transitioning into increasingly recognizable sleep and wake cycles, although these are not yet similar to those of newborns.

The baby is swallowing amniotic fluid and is being introduced to certain smells and tastes. Taste and smell are continuously stimulated through the amniotic fluid, and this fluid varies slightly depending on the mother's diet.

The baby is swimming in the amniotic fluid, and there is still quite a bit of space in the womb. It is constantly moving throughout the day: turning, kicking, stretching its arms and legs, and changing positions, which will change as it grows in the third trimester.

The baby's sleep rhythm in the womb is very different from the sleep patterns after birth and does not resemble the sleep patterns of adults either. They alternate between short sleep periods and intense activity moments, making it feel like they are constantly moving at different times of the day and night.

Development of the Baby's Inner Ear at 24 Weeks

Hearing is one of the most complex sensory organs and is one of the earliest developing organs during pregnancy. It is divided into three sections: outer, middle, and inner ear, and each of these sections has its own maturation rhythm, but they are perfectly coordinated.

From the early weeks of pregnancy, structures that will allow the baby to hear begin to form:

• In weeks 4-5, a small sac appears that will enable the formation of the inner ear.
• In week 8, the ear canal, the outer ear, and the base of the middle ear begin to be defined, including future bone chains.
• Between weeks 8-10, the cochlea and semicircular canals form as vital structures for hearing and balance.
• In the 16th week, the middle and inner ear are almost completely structured, and the first sensory cells begin to activate.

The cochlea is the first major hearing structure that converts sound waves into electrical impulses and transmits them to the brain. However, the auditory cortex of the brain continues to develop after birth, which explains that the ability to distinguish fine sounds and language will significantly improve in the first months after birth.

By the 22nd week, the baby begins to hear sounds clearly coming from the mother’s body, such as heartbeats, breathing, or blood flow. In the 23rd and 24th weeks, it can also perceive sounds from outside, but these sounds come filtered through layers such as skin, uterine wall, and amniotic fluid.

At this stage of pregnancy, the auditory system begins to distinguish low-frequency sounds better than high-frequency sounds, making male voices and low-frequency noises heard more clearly. As hearing and the brain mature, the baby expands the range of sounds it can perceive and distinguish.

What Sounds Does the Baby Hear in the Womb?

In the womb, the baby is surrounded by amniotic fluid, which acts as a natural filter. This water environment reduces the intensity of sounds but does not completely block them, so the fetus lives in a constant sound environment.

The main sounds the baby perceives are:

• Mother's voice: the clearest, continuous, and meaningful sound. It is transmitted not only through the air but also through bone vibrations via the mother’s body, making it particularly pronounced for the fetus.
• Mother's heartbeat and breathing: creates a rhythmic background sound that provides a sense of peace and security.
• Digestive system sounds: intestinal movements, gas passing, and other internal sounds create the acoustic landscape inside the womb.
• External sounds: external sounds like conversations, music, and traffic noise come weakened, but are recognizable, especially in the second and third trimesters.

Research in the field of neuroscience has shown that newborns prefer their mother's voice over other sounds, indicating that auditory learning begins in the womb. It has also been proven that babies can recognize melodies they have repeatedly heard during pregnancy.

Between approximately 14-16 weeks, the fetus may start to hear whispers from the mother’s body and may respond by increasing heart rate and accelerating body movements. In the third trimester, responding to external sound stimuli becomes more pronounced: the baby may startle at very loud sounds or calm down with the voice of caregivers.

The fetus generally prefers soft and melodic music and avoids loud noises and excessive noise. Intense and prolonged sounds can be stressful for the baby, especially if the mother is constantly exposed to very noisy environments.

The Connection Between Fetal Hearing and Learning

The fetal brain not only receives sounds but also begins to process them and form memories. Auditory stimulation in the womb plays a role in emotional maturation and future language acquisition.

Various studies have shown that:

• Fetuses can recognize rhythmic patterns and melodies before birth and can respond differently to familiar and unfamiliar sounds.
• Newborns show familiarity responses to songs or stories they have repeatedly heard during pregnancy (such as changes in heart rate or sucking).
• Early exposure to the mother’s voice and language is associated with the development of speaking and listening skills after birth.

This does not mean that music or special messages will increase the baby's intelligence during pregnancy, but it shows that sound is a real connection and a pathway for intrauterine learning. Talking to, singing to, or reading stories to the baby are simple and natural ways to promote auditory development without the need for special devices.

In any case, it is important to avoid prolonged exposure to loud sounds. Continuous exposure to intense sounds can be harmful to both the mother and the fetus. If you are working in a noisy environment, it is recommended to discuss protective measures with your healthcare professional.

Tests to Be Done at This Stage

It is time to perform a comprehensive blood and urine analysis, which is important for assessing your health status and timely detecting potential complications such as anemia or gestational diabetes.

Your urine will be analyzed in all trimesters. Even if you have no symptoms, there may be bacteria in the urine, which can lead to contractions or upward urinary tract infections. Detecting these asymptomatic bacterial infections allows for treatment before problems arise.

If you have not had toxoplasmosis, markers will be requested again to ensure you do not contract it during pregnancy. This check is especially important if you live with cats or consume risky foods such as undercooked meats or poorly washed vegetables.

Additionally, parameters indicating that you are starting to develop anemia will also be analyzed. This is not a rare condition; on the contrary, there is a specific physiological anemia during pregnancy. The increase in circulating fluid volume means that the blood is diluted, which is referred to as hemodilution anemia.

From the second trimester onwards, real anemia may develop due to the increased iron needs of the baby, which may require treatment. In this case, iron supplements will be prescribed to you, and you should follow the instructions to enhance absorption and reduce digestive discomfort.

This analysis also includes tests to detect gestational diabetes. The O’Sullivan test is typically performed, which is a screening test, meaning it is an initial approach to identify women at high risk for diabetes.

It is done on an empty stomach. First, a blood sample is taken, and then a drink containing 50 g of glucose is given; after one hour, another blood sample is taken to measure how your body reacted to this sugar load.

If the blood sugar value exceeds 140 mg/dl, you will need to undergo an Oral Glucose Tolerance Test or “long curve”, which is a diagnostic test.

In this test, you will be given 100 g of glucose instead of 50. A blood sample will be taken on an empty stomach, and three more blood samples will be taken at different intervals after consuming the glucose syrup. If glucose values are abnormal in two or more measurements, a diagnosis of gestational diabetes will be made.

Some hospitals conduct an intermediate test with 75 g of glucose. In this case, a carbohydrate-rich diet is recommended three days before the test, and blood samples are taken three times: once on an empty stomach and twice after consuming the syrup. This is also a definitive test; if one of the three values is abnormal, a diagnosis of gestational diabetes will be made.

If a diagnosis of diabetes is made during pregnancy, an endocrinologist will recommend a special diet and ask you to monitor your blood sugar before and after meals. If the values remain within the recommended limits, the diet will be sufficient; otherwise, insulin therapy may be necessary.

What is Gestational Diabetes?

It is a type of temporary diabetes that occurs during pregnancy, characterized by high blood sugar levels detected for the first time during pregnancy.

It occurs due to the effects of certain hormones released by the placenta, which partially inhibit the action of insulin in the mother's body. As a result, the body has to produce more insulin to keep blood sugar levels stable.

If the mother's pancreas cannot release all the insulin required during pregnancy, blood sugar levels rise and gestational diabetes occurs. This condition affects approximately 5-10% of pregnant women, depending on risk factors in each population.

This is not just a problem for the mother; gestational diabetes can also cause changes in our baby. It can promote the baby having a very high birth weight (macrosomia), complicate deliveries, and increase the risk of cesarean sections.

Additionally, after the child is born, they may experience difficulties regulating their own blood sugar levels, and may require special monitoring in the hospital due to the risk of hypoglycemia in the first hours after birth.

For all these reasons, it is very important to properly diagnose and manage gestational diabetes. By following recommendations for nutrition, appropriate exercise, and insulin therapy if necessary, most women can have a normal pregnancy and reduce risks for the baby.

When the pregnancy ends, this type of diabetes usually disappears. However, some women are at risk of developing type 2 diabetes throughout their lives, especially if there are other factors such as obesity or family history. Therefore, it is recommended to have periodic blood sugar checks after birth and to maintain healthy habits in the long term.

Tinnitus During Pregnancy

If you are pregnant and experiencing ringing in your ears, it can be distressing, especially if you have never felt anything like this before. This constant or intermittent sound, sometimes described as a beep, whistle, or whisper, is known as tinnitus or ringing in the ears.

Traditionally, it has been associated with various disorders (such as hearing problems or vascular issues), but in recent years, it has been acknowledged that some women develop tinnitus during pregnancy, even if they have never experienced such a condition before.

The ringing in pregnancy is associated with the hormonal and vascular changes that come with pregnancy and is also linked to an increase in blood volume and, in some cases, a slight increase in blood pressure.

Being pregnant and experiencing tinnitus is often described as sounds accompanying the heartbeat, meaning a type of tinnitus that comes with the heartbeat. In women who experienced tinnitus before pregnancy, this condition may become more intense or pronounced due to hormonal and circulatory reasons.

The good news is that in most cases, these ringing sensations are temporary. They typically increase during the last months of pregnancy and the first weeks after birth, then gradually decrease.

Additionally, an increase in tinnitus has been observed in women undergoing hormone therapy during menopause. Fluid retention, headaches, and increases in blood pressure can worsen the perception of ringing.

If these sounds in the ears are very intense, accompanied by dizziness, hearing loss, or pain, it is important to consult a healthcare professional to rule out other causes and assess whether a more comprehensive hearing evaluation is necessary.

The hearing ability of both the mother and baby is at a significant sensitivity stage during pregnancy. Protecting the sound environment, avoiding prolonged loud noises, following regular check-ups, and consulting any noticeable symptoms helps preserve this important sense.

This stage of pregnancy marks a milestone where the baby develops the ability to listen, learn, and connect through sound, while medical check-ups, monitoring the mother's health, and early detection of issues like gestational diabetes allow for a more peaceful progression into the final weeks of pregnancy.