Objectives To gather more evidence on a possible relation between spina bifida and agricultural and other occupations of parents, a register-based linkage study was conducted in Sweden.

Methods Four hundred and eighty-two cases of spina bifida in infants born between 1976 and 1991 were identified from the Swedish Register of Congenital Malformations. Nine hundred and sixty-four referents without spina bifida were selected from the Medical Birth Register and matched for year of birth of the child, maternal age, and parity. Information on occupation was obtained from the Medical Birth Register from 1983 on, and from the census, which is performed every fifth year.

Results A slightly increased odds ratio (OR) was observed for women in agricultural occupations [OR 1.8, 95% confidence interval (95% CI) 0.8--4.2]. For all women who had an agricultural occupation or lived on a farm, the OR was 2.2 (95% CI 1.3--3.8). The OR values of most of the other occupational groups were close to unity.

Conclusions The results suggest an increased risk of spina bifida for the infants of women in agricultural occupations, but they do not provide insight into any specific occupational risk factors.

Key terms birth defect; neural tube defect; occupational exposure