Risk of limb birth defects and mother's home proximity to cornfields

Background: Although previous studies have linked proximity to crops and birth defects, they lacked individual-level exposure data and none was based on using planted area instead of linear proximity to crops as the exposure metric. We studied birth defects in relation to the area of corn or soybeans within 500 m of the mother's residence. Methods: We selected all singleton births from rural areas conceived during the 2000-2004 spring-summer months (n = 48,216). We determined whether the area with corn or soybeans around the home was associated with birth defects using multiple unconditional logistic regression. Results: We found that limb birth defects (ICD-9-CM 754.5, 755) increased in relation to cornfields (Adjusted OR = 1.22; 95 % CI = 1.01, 1.47 per additional 10 ha planted with corn within 500 m). None of the birth defect types studied was associated with soybeans. Conclusions: In the Midwest, a significant and expanding proportion of the population is now living in close proximity to cornfields. Our results suggest that additional studies should be conducted to identify which factor(s) associated with cornfields are behind the observed increase in limb birth defects. (C) 2009 Elsevier B.V. All rights reserved.