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37: Agricultural-related chemical exposures, season of conception and risk of gastroschisis in Washington state

      Objective

      The prevalence of gastroschisis has increased 2- to 4-fold and may occur more frequently among pregnant women living in rural areas. Atrazine, a teratogen in animal studies, is a commonly used herbicide. We sought to determine if increased peri-conceptional and first trimester maternal exposure to atrazine and other agricultural chemicals is associated with risk of development of gastroschisis.

      Study Design

      We conducted a retrospective case control study using the Washington State Birth Certificate (1987-2006) and the US Geological Survey (2001-06) databases. Cases included all live-born singleton infants with gastroschisis. Controls were randomly selected from all Washington State singleton live births in a 4:1 ratio and frequency-matched to cases by year of birth. Chromosomal anomalies or syndromes were excluded from both groups. High chemical exposure levels in surface water were defined using Environmental Protection Agency standards. We calculated the distance between a woman′s residence and the closest site of high exposure to atrazine, nitrates, and 2, 4-dichlorophenoxyacetic acid. Multivariate logistic and linear regressions were used to estimate the association between toxic surface water levels of agricultural chemicals and risk of gastroschisis.

      Results

      805 cases and 3616 controls were identified. Gastroschisis occurred more frequently among infants whose mothers resided <25 km from a site of high surface water contamination with atrazine (OR=1.6, 95% CI 1.1–2.3). The risk of gastroschisis was inversely related to the distance between maternal residence and the closest toxic atrazine site (p=0.05). No increased risk was seen with other compounds. The risk of gastroschisis increased if conception occurred in the spring (March-May; OR=1.2, 95% CI 1.1-1.5). In multivariate analysis, nulliparity, tobacco use and spring conception remained as significant predictive factors for gastroschisis.

      Conclusion

      Maternal exposure to elevated atrazine levels in surface water is associated with fetal gastroschisis, particularly among women who conceive in the spring.