Maternal occupation in agriculture and risk of limb defects in Washington State, 1980-1993.

Objectives: This study examined the association between maternal occupational exposure to agricultural chemicals and the risk of limb defects among offspring.

Methods: A retrospective cohort study was conducted using Washington State birth records for the years 1980 through 1993. The exposed group, consisting of 4466 births to mothers employed in agriculture, was compared with 2 reference groups: (i) 23,512 births in which neither parent worked in agriculture ("nonagricultural" group) and (ii) 5994 births in which only the father worked in agriculture ("paternal agriculture" group). The outcome of interest was limb defects [syndactyly, polydactyly, adactyly, and "other limb reductions" (as listed in the birth record)].

Results: An elevated risk of limb defects was observed for the exposed group in comparison with both the nonagricultural and paternal agriculture groups, with ethnicity-adjusted prevalence ratios of 2.6 [95% confidence interval (95% CI) 1.1-5.8] and 2.6 (95% CI 0.7-9.5), respectively.

Conclusions: These results support the hypothesis that maternal occupational exposure to agricultural chemicals may increase the risk of giving birth to a child with limb defects.