Is gastroschisis associated with county-level socio-environmental quality during pregnancy?
Background: The prevalence of gastroschisis more than doubled between 1995 and 2012, yet its etiology remains largely unknown. Individual-level risk factors for this major abdominal birth defect include young maternal age, low body mass index (BMI), and some environmental exposures. Spatial variation in the distribution of gastroschisis suggests that community-level environmental and/or sociodemographic factors may contribute to the etiology of gastroschisis, though few studies have rigorously examined this possibility.
Methods: We used the U.S. Environmental Protection Agency’s (EPA) Environmental Quality Index (EQI), a county-level estimate of cumulative exposures in five domains – air, water, land, sociodemographic, and built environment – to assess the association between ambient environmental quality during early pregnancy and gastroschisis in the National Birth Defects Prevention Study, a population-based case-control study conducted in multiple U.S. states. Our analysis included 594 cases with gastroschisis and 4105 infants without a birth defect (controls) delivered between 2006 and 2011. The EQI was categorized into tertiles based on the national distribution of EQI values and then linked to geocoded self-reported residence at conception. The lowest tertile category, which represents “better” environmental quality, was used as the reference. Using logistic regression, we estimated adjusted odds ratios (aOR) and 95% confidence intervals (CI) adjusted for maternal age at conception, race/ethnicity, education, and pre-pregnancy BMI.
Results: The overall EQI was modestly associated with gastroschisis: the aOR (95% CI) for maternal residence in counties with poorer environmental quality (highest tertile) was 1.3 (1.0, 1.7), compared to the reference (better environmental quality). Within domain-specific indices, only the sociodemographic domain was moderately associated with gastroschisis when comparing poorer to better environmental quality: sociodemographic 1.5 (1.0, 2.3); air 1.0 (0.8, 1.3); water 1.1 (0.8, 1.5); land 1.2 (0.9, 1.5); and built environment 1.0 (0.8, 1.4).
Conclusions: Our finding that the sociodemographic domain of the EQI was associated with gastroschisis is consistent with previous studies. Future work could elucidate pathway(s) by which components of the sociodemographic domain such as county-level housing quality, unemployment rates, and crime – or possibly related psychosocial factors like chronic stress – potentially contribute to risk of gastroschisis.