Prolonged exposure to loud noise can be unsafe for pregnant mothers and the growing fetuses. This may increase stress and affect hearing in pregnant women. The risk of hearing problems in the baby is higher in cases where the mother is exposed to high noise levels, such as noise from a rock concert or a jackhammer (1).
Read this MomJunction post to know more about the impact of loud noises on a pregnant mother and fetus, safe levels of sound, and how to protect yourself from high noise exposure.
What Kind Of Sounds Are Dangerous For Pregnant Women?
Unpleasant or unwanted sounds are referred to as noise. Noise is everywhere around us, including the noise that could emanate during household chores or at the workplace. However, not all noises are detrimental to pregnant women.
The following are examples of high levels of noise pollution (1).
- Sounds from traffic or aircraft (jet planes)
- Factory sounds
- Emergency sirens
- Gunshot and explosions
- Rock concert and loud music
- Tractors used in farm
- Sounds from loud machines, like a chainsaw
It is usually continuous noise exposure and exposure to loud noises that are dangerous. Remember, if a noise is unpleasant to you, then it is likely to be harmful to the developing baby.
How Do Loud Noises Impact Pregnant Women?
The health impact due to noise may vary depending on frequency (how often), duration (how long), and intensity (how much) of the noise.
The following side effects might occur due to prolonged exposure to noise.
- Hearing impairment: High exposure to noise may cause damage to the auditory system. The noise-induced hearing impairment can be accompanied by a distorted perception of sounds and tinnitus (ringing in the ear) (2).
- Sleep disturbances: Environmental noise could cause sleep disturbances. Uninterrupted sleep is essential for physiological and psychological health. Sleep disturbances may also contribute to stress (2).
- Increased production of stress hormones: Pregnant women may have increased risk of stress due to exposure to high noise levels. High levels of stress hormones may increase the risk for low birth weight and premature birth (3).
- Increased risk of cardiovascular disease: Physiological stress reactions due to noise may include activation of the autonomic nervous system and endocrine system. Changes in these systems may cause an increased risk of cardiovascular diseases as an outcome of alteration in factors such as blood pressure, lipid levels, cardiac output, etc (4).
- Increased risk of premature delivery: Women who are exposed to sounds of more than 80 decibels during eight hours of occupation tend to have a high risk of premature birth (5).
- Low birth weight: Several studies have noted that pregnant women who reside close to airports are regularly exposed to aircraft noises louder than 60 decibels. The constant exposure, throughout day and night, might result in low birth weight in babies (5)
Although mothers can protect their hearing using earplugs, these sounds can reach the womb and affect babies’ hearing (1).
The Effects Of Loud Noise On The Baby During Pregnancy
Some noises could cause fetal hearing problems within first time exposure, whereas a few may harm over continued exposure.
The continuous exposure to high noise levels during intrauterine life may result in fetal abnormalities and preterm birth. These adverse effects include (5):
- High-frequency hearing loss
- Growth retardation
- Damage of cochlea
- Premature birth
- Birth defects
Expected mothers’ exposure to impulse noises, such as gunshots and explosions, including those from fireworks, can be dangerous to the human fetus. The long-term effects on the baby can include damage to the inner ear, which can result in noise-induced sensorineural hearing loss over time.
Are Unborn Babies Protected Against Loud Sounds?
Hearing damage in babies due to continuous exposure to high-level noise while in the womb could indicate that the developing fetuses may not have protection against loud sounds. Fetuses start responding to low frequency sounds earlier, and higher frequency sounds during later gestation weeks.
Maternal abdomen and uterus may filter high-frequency sounds and lower decibel sounds. However, this may not effectively block intense and sustained noises of high or low frequencies and higher decibel levels (6).
Some clinical studies have shown that there is high-frequency hearing loss in children with a history of exposure to noise more than 85 decibels during the gestation period (5). These instances indicate that the baby may not entirely be insulated from noises while inside the womb.
Recommended Noise Levels During Pregnancy
There is no precise, appropriate, and safe sound pressure level (measured in decibel) for women during pregnancy. Sounds can travel through the body and reach the developing baby.
Some experts believe that pregnant women should avoid continuous noise exposure to sounds louder than 115 decibels (1). However, staying way below 115 decibels noise limit is preferable. A nationwide prospective cohort study conducted among Swedish women had shown that occupational noise of more than 85 decibels caused a reduction in fetal growth. It was observed in full-time working mothers (7).
According to the US CDC, noise that is 85 decibels or more can be hazardous to the hearing of adults. Therefore, as per the results noted in studies and CDC’s recommendation, it is best to limit your exposure to noises lower than 85 decibels to avoid causing adverse effects to you and your fetus (5).
How To Prevent Noise Exposure During Pregnancy?
There is usually no way to tell if a sound is 85 decibels or more since the noise could come across as tolerable. Also, avoiding exposure to loud noises during pregnancy may not be easy for all women, especially those who reside in urban areas or have occupational exposure.
Nevertheless, you may take the following measures in your day-to-day life to reduce your exposure to noise.
- Keep noisy machines such as washing machines or dishwashers away from your living areas or bedrooms
- Try to spend more time in silent areas such as the library, or any other quite spot
- Reduce continuous use of headphones or earphones with high volume
- Avoid exposure to rock concerts, loud music, noisy movies, and noisy machines
- Stay indoors when there is the use of fireworks in your vicinity
- If you have noise exposure at your workplace, then you may discuss it with your organization and try to avoid it as much as possible
Do note that wearing earplugs can limit your exposure to noise, but it may still cause noise to reach the fetus.
If you are residing in industrial areas or near airports, then you could consider soundproofing your home with wall coverings, carpets, and acoustic foam panels.
Frequently Asked Questions
1. When do babies start hearing in the womb?
The structures for hearing or auditory systems begin to develop by three to six weeks of gestation and are well established by 20 weeks of pregnancy.
Fetus’ ability to hear has been noticed around 24 weeks of gestation during antenatal (prenatal) ultrasound examinations. Fetuses produce a blink-startle response to vibroacoustic stimulation (low-frequency sound and vibration) during the ultrasound (5). This startle reflexes can be a sign that the fetus hears the low-frequency sound of the ultrasound transducers.
2. What does it sound like inside the womb?
The fetus may hear a lot of sounds during intrauterine life. The auditory stimulus inside the womb can be (5):
- Mother’s voice
- Placental blood flow
- Mother’s heartbeat
- Mother’s breathing sounds
- Vibroacoustic stimulations during an ultrasound
- Sounds from the mother’s bowels
The following sounds from the workplace, household sources, or the surrounding environment can also create some response from the fetus. The external sounds may include:
- Occupational noises
- Traffic noises
- Vacuum cleaners
- Mobile phone
- Washing machine
- Loud conversations
These intrauterine sounds may not be harmful to babies. However, they should be protected from loud noises from external sources.
According to available data from the World Health Organization, there was an increase in cases of hearing dysfunction from 1.2 million in 2008 to 1.4 million people in 2017 (8). The rise in noise pollution could be a reason. Avoiding noisy environments and exploring a provision for a quieter place to work can help keep you and your growing baby protected.
2. Adverse Health Effects Of Noise; The World Health Organization
3. Mary E Coussons-Read; Effects of prenatal stress on pregnancy and human development: mechanisms and pathways; The United States National Library of Medicine (NLM)
4. Chronic health effects and injury associated with environmental noise pollution; The Centers For Disease Control And Prevention
5. Noise as a Health Hazard for Children: Time to Make a Noise about it; The Indian Academy of Pediatrics
6. Charlene Krueger, Et Al.; Safe Sound Exposure In The Fetus And Preterm Infant; The United States National Library Of Medicine (NLM)
7. JennySelander, et al.; Full-time exposure to occupational noise during pregnancy was associated with reduced birth weight in a nationwide cohort study of Swedish women; sciencedirect
8. Hearing loss: rising prevalence and impact; The World Health Organization