We know that loud noises can cause stress and hearing loss in adults. The same may also be true for a baby that is still in the womb. The mother’s abdomen, the uterus, and the amniotic fluid help to suppress sounds and noises for the fetus; however, constant loud noise, such as earphones placed on the mother’s stomach, may contribute to negative effects on the fetus.
Noise levels: Noise is measured using decibels. Noise that is 70 decibels can be annoying to a listener, but 80 decibels is when noise can become damaging to a person’s hearing. Hearing is fully developed in the fetus by week 24 of gestation.
Table 1. Noise decibels associated with common sounds
|Breathing||0-10 decibels||Hearing level|
|Quiet conversation||50 decibels||Quiet|
|Background music||60 decibels|
|Typical factory||80 decibels||Potential for hearing damage|
|Busy urban street||90 decibels|
|Jet take-off||100 decibels||Hearing damage if >1 minute|
|Stereo near human ear||110 decibels|
|Loud rock concert||120 decibels||Max pain level|
|Earphones at loud level||130 decibels|
|Exploding firecracker close to human ear||150 decibels||Eardrum rupture|
Sources of loud noise: You can hear loud noises outside or inside from machines, electronics, cars, or other people. Some pregnant women may even deal with loud noises in their workplaces. Many studies have evaluated the frequency and effects of loud noises in neonatal intensive care units (NICUs). Some NICUs have consistently loud noise levels from staff, visitors, and machines that could potentially cause hearing damage in newborns.
- A study in Sweden found that daily workplace noise levels >85 decibels compared to <75 decibels, in pregnant women working full-time, increased the risk of hearing problems in children.
Effects of loud noise: Loud noises can cause stress, increased blood pressure, and hearing loss in adults. Despite the protective surroundings of the womb, a fetus may be at risk for hearing damage with prolonged exposure to loud noises in utero. Potential adverse effects associated with loud noise exposure in children include hearing damage or hearing loss, stress, sleep disturbances, and learning impairments. The effects of loud noise on fetal health are not as well studied as the effects in children, teenagers, and adults, but fetal adverse effects are thought to include growth issues and hearing loss.
- A large analysis of 29 small studies found that chronic noise during pregnancy did not affect a baby’s birth weight or cause preterm birth, birth defects, or death.
- Another analysis of multiple trials found that pregnant women exposed to consistent sounds levels >80 decibels had a higher risk of developing gestational high blood pressure and a higher risk of having small newborns or newborns with birth defects. This study found no links between loud noise and preterm birth or fetal death.
Recommendations: The American Academy of Pediatrics recognizes that loud noise can be detrimental for a fetus and for children. Different organizations within the United States publish guidance on appropriate and inappropriate noise levels during pregnancy.
Table 2. Recommendations around avoiding fetal and newborn exposure to loud noise
|Centers for Disease Control and Prevention||Guidelines for pregnant women in noisy workplaces||Avoid noises >115 decibels during pregnancy|
|Sound Group Study||Guidelines for noise in the NICU||Fetus:
• Avoid noises >65 decibels during pregnancy
• Do not place earphones/headphones on your stomach during pregnancy
• Avoid playing music for your baby while he or she is still in the womb
• Avoid hourly continuous sound levels >50 decibels
• Avoid hourly noise levels >55 decibels for 10% of the time measured
• Max noise levels should not be >70 decibels
• Do not use earphones/headphones for infants