Occupational noise exposure and course of pregnancy.

The study examined the possible relation of occupational noise exposure to adverse pregnancy outcomes. The experience of 1,190 reference mothers from a case-referent study based on the Finnish Register of Congenital Malformations was scrutinized. Exposure to noise was blindly assessed from a description of the mother's workday by two industrial hygienists. Women with an estimated level of noise of around 80 dB LAeq(8 h) or higher were considered exposed. Threatened abortion was not associated with noise exposure alone, but, when it was combined with shift work, the adjusted risk was over twofold. The adjusted risk of pregnancy-induced hypertension was twice as high among the mothers exposed to noise in shift work, and the duration of their pregnancy was shorter. The analyses produced indications of a relation between noise and growth retardation which was not connected with shift work. There were significantly ascending trends in the proportions of these outcomes according to increasing exposure intensity.