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Global Bioweather

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Noise and the unborn child

Researchers have established a possible link between the stress of women during pregnancy and embryo development, in particular foetal growth retardation, reduced birth weight, premature births, possible birth defects, and a higher risk of the baby developing cardiovascular or metabolic diseases later in life.

One response to stress, whether from noise or other sources, is the constriction of blood vessels, resulting in a reduced blood flow to the uterus. According to a study, published in the International Journal of Hygiene and Environmental Health in 2003, the reduced blood flow is most noticeable during week two to nine after conception. Tentative statistical evidence points to lower birth weights, premature births, and birth defects, such as a cleft lip or palate and abnormal spine growth, after excessive maternal stress. While other studies have confirmed the link with lower birth weights and premature births, the link with birth defects is less clear.

It doesn't take much to imagine that a very frightening noise, such as a gunshot or an explosion, may tense the muscles of a pregnant woman and involuntarily induce contractions and pre-term labour. Noise events don't have to be so dramatic to lead to pre-mature births, though. Several studies have associated excessive noise exposure to shortened periods of gestation.

This, of course, should be of concern to expecting mothers who are subjected to stress and who are living or working in noisy environments. Not enough research has been conducted to recommend any noise levels above which the baby is likely to be harmed.

You probably heard the saying that you should play Mozart to a baby in the womb so it becomes more intelligent. This may be a myth, but it is a fact that the unborn can hear the outside world. At latest from the fourth month onwards, the child in the uterus begins to perceive sound. At the sixth month, the ear is anatomically fully developed.

It has been demonstrated that unborn babies to react to loud noise with body movements and increased heart rates. Noise transmits easily into the uterus and there is, therefore, enough reason to suggest that the baby's body responds similarly to noise as an adult does, including some loss of hearing when exposed to excessive noise. In a Canadian study, three times as many children of mothers who worked in a noisy environment of between 85 to 95 dBA during pregnancy recorded some high-frequency hearing loss when compared to children of mothers who worked in quieter environments.

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Global Bioweather

Noise and the unborn child

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Noise