Managing Noise Exposure During Pregnancy

Exposure to occupational noise has been identified as a risk factor for hearing impairment in working adults. 

The Health and Safety Executive (HSE) estimate that more than 2 million people in Great Britain are exposed to unacceptable levels of noise at work. Types of exposure may loud machinery, power tools, hammering, drop forging, warning sirens, vehicles, loud music, crowds, any loud impacts, guns and explosive sources, amongst many others across a wide variety of industries.

However, minimal guidance and few studies have assessed the effect of occupational noise exposure during pregnancy and specifically to the foetus.

Potential risks for the mother

• Noise induced hearing loss or irreversible damage to the inner ear caused by exposure to loud sound. This may be gradual, cumulative damage over a long period of time or sudden trauma to the inner ear from a single noise source for a short period of time.
• Prolonged exposure to loud noise can increase blood pressure, stress and tiredness, during a time when mothers are already under significant physiological and psychological pressure.

Potential risks for the foetus

• Increased blood pressure, stress and tiredness in the mother may affect foetal development. Some studies have indicated that women exposed to high noise levels during pregnancy are at a significantly higher risk for having small-for-gestational-age, gestational hypertension and an infant with congenital malformations.
• Sound can be transmitted from the air over the abdominal wall and the uterus to the foetal head during pregnancy, which could cause noise induced hearing loss – a foetus’ ears develop around the 20th week of pregnancy and start responding to sounds around the 24th week. 
• Noises from outside the mother’s body are typically lower inside the womb, but not completely silenced. Sound can stimulate the foetus’ inner ear through a soft tissue conduction route, which could potentially affect the hearing of the foetus by damaging inner and outer hair cells within the foetus’ cochlea. 

Experimental studies show that the attenuation of noise through the passage of the abdominal wall and the uterus is strongly dependent on frequency. Although the foetus is well protected from high-frequency noise, low-frequency noise can be amplified during the passage of the abdominal wall and the amniotic fluid. Therefore controlling a pregnant mother’s exposure to noise through means of hearing protection will not protect the foetus’ hearing. 

A study including over 1.4 million births in Sweden between 1986–2008 has indicated that pregnant mothers with occupational daily average noise exposures at or above 85 dB(A) showed increased risk of hearing impairment / dysfunction in the child when compared with those mothers with lower daily noise exposures [75-84 dB(A)].

UK Law

The Control of Noise at Work Regulations 2005 require employers to take action to prevent or reduce risks to health and safety from noise at work. They are designed to protect against risks to both health and safety from exposure to noise in the workplace. 

Regulation 4 sets out Exposure Limit Values (ELV) – the levels of exposure to noise above which an employee must not be exposed and Exposure Action Values (EAV) – the levels of exposure to noise at which employers are required to take certain actions. They are expressed as daily or weekly average exposures and also peak sound pressures (extremely loud short bursts or peaks of noise). 

There are currently no adjustments to these limits for pregnant workers. However it is stated that some workers should be given particular consideration within a risk assessment, this includes pregnant women.

General guidance from the HSE on pregnant workers states that upon being informed of pregnancy the employer must carry out a specific individual risk assessment to identify risks to the mother and unborn child. Exposure to noise is listed as a common risk to pregnant workers. If the employer identifies a significant risk to mother or child, they must control this risk.

Control measures could include:

• ensure there is an up-to-date noise risk assessment for the individuals role;
• avoiding low frequency noise tasks (noise that you can feel as a rumble or vibration are very low frequency sounds);
• avoiding body contact of pregnant workers with any source of noise or vibration. Sounds are stronger to a developing foetus when your body is closer to the source of the noise.

If employers cannot control or remove the risk, they must temporarily adjust the expectant mother’s working conditions and/or working hours, or if that is not reasonably practicable; offer her suitable alternative work if available or as a last resort; suspend her from work on paid leave for as long as necessary to protect her health and safety, and that of her child.

Consult an occupational health professional for further advice if you are worried about any issues affecting pregnant workers or an unborn child.