During pregnancy loud noise can affect your hearing and increase your stress levels. According to the CDC it may even increase your chances of having a baby with hearing problems. 

Studies have shown that constant exposure to loud or discordant music can change an animal’s brain structure, and inhibit a plant’s growth, and it may even damage an unborn baby's hearing.

Developing fetuses can react to loud music and noises, usually starting around 22 weeks of the pregnancy, and different types of music can cause colic in babies (already born). By the 22nd week of gestation, your baby’s cochlea will be fully formed. The cochlea is a portion of the inner ear that enables hearing. After the 22nd week, your baby can hear everything you hear, although sounds in the higher frequencies will be slightly muffled.

According to several studies, indoor and outdoor environmental noise pollution have been documented as a serious health hazard with increasing adverse effects on fetus, infants, children, adolescents and adults. Noise induced hearing loss and non-auditory adverse effects due to noise pollution, are being increasingly diagnosed in all age groups including the fetus.

Studies have shown women who work in an environment that requires hearing protection have babies with higher rates of hearing loss, and there is growing evidence that excessive noise can harm a developing fetus.

The loudness of sounds is measured in decibels (dB). And potential problems related both to decibels as well as the length of exposure. The louder the sound and the longer the exposure, the faster damage will occur.

Here are some decibel ranges:

• 30 dB: Quiet whisper
• 80 dB: Telephone dial tone
• 85 dB: City traffic inside a car
• 107 dB: Power mover
• 110 dB: Stereo headset
• 125 dB: sandblasting, Loud rock concert
• 140 dB: Jet engine at 100', Gun noise for
• 194 dB: Loudest sound possible, death of hearing tissue

OSHA Permissible Sound Level Exposure:

• 90 dB: 8 hours per day
• 100 dB: 2 hours per day
• 110 dB: 1 hour per day 

For example, eight hours of exposure to 90 dB industrial noise daily is considered relatively safe for most people. However, using power tools (100 dB), listening through a stereo headset (110 dB) or attending a rock concert (about 120 dB) may damage hearing after just a few exposures and after 30-60 minutes.

Amniotic fluid protects your growing baby only to some extent. Amniotic fluid slightly muffles noises that are high pitched. But studies have shown that it also amplifies noises in the low range and loud noise can negatively affect the growing fetus.

So to be safe when pregnant, avoid any situation that exposes your baby to loud noise  for extended time periods.