What Does Baby Hear in the Womb?
Did you know that fetuses can recognize some sounds?
The sensory cells of the ear mature around the 20th week of gestation. They become functional between the 25th and 29th week, before the fetus’s organs are fully formed.
A healthy fetus is able to respond to sounds. The acoustic environment in utero is dominated by the mother’s heartbeat, voice and breathing, as well as placental sounds. Those sounds are accompanied by external noises; the fetus might respond to music or parents’ voices.
Noise Exposure during Pregnancy
During the last trimester, the auditory system is fully formed. The inner ear cells activate when a sound arrives and transmit the sound signal to the brain through the auditory nerve. While most sounds are muffled by the mother’s abdominal wall and the amniotic fluid, low-frequency sounds are more audible because sound waves travel more easily at low frequency. The practical guideline of the Comité médical provincial d’harmonisation, Pour une maternité sans danger, issued a recommendation about the potential risks of workplace noise exposure during pregnancy. During a normal pregnancy, from the 20th week of gestation onward, it is recommended to “limit sound levels in the workplace to below 85 dBA (Leq, 8h) because of sufficient evidence of increased risk of low weight for gestational age (27% increase) and a suspicion of increased risk of preterm birth (13% increase), and gestational hypertension (42% increase)”. Medical advice may be required for atypical pregnancies. Data in the literature is not sufficient to conclude that workplace noise exposure poses a potential risk to fetal hearing. However, it is important to mention that a lack of evidence in the literature doesn’t necessarily mean that there is no risk.
Furthermore, it is not recommended to put headphones directly on a pregnant woman’s belly to make the fetus listen to music. The sound reaching the fetus’s ears may be amplified, leading to a possible risk to hearing health.
Hearing Development - From 0 to 12 months old
From birth: Baby recognizes mother’s voice From 3 to 4 months old: Baby reacts to loud sounds by jumping or blinking From 3 to 6 months old: Baby starts turning towards a sound From 6 to 10 months old: Baby starts babbling and understands when we say “no” From 8 to 12 months old: Baby actively tries to imitate sounds
Hearing screening can be performed at birth. It is also recommended to have your child’s hearing tested if in doubt.
For more information, talk to an ENT specialist or a pediatric audiologist.
