Associations between occurrence of birth defects and hydraulic fracturing activities in Barnett shale region, Texas.

The impacts of hydraulic fracturing (HF) on birth defects have been suggested by previous studies but remain largely inconclusive. In this study, we assessed whether pregnant women who lived in areas with high HF activities had increased risks of giving birth to offspring with overall or specific birth defects, including atrial septal defect (ASD), ventricular septal defect (VSD), patent ductus arteriosus (PDA), microcephaly (MIC), and hydrocephaly without spina bifida (HSB). All live births between 1999 and 2014 among the residents in the four core counties of Denton, Johnson, Tarrant, and Wise in the Barnett Shale region, Texas, were analyzed. Standardized Morbidity Ratio (SMR) and Poisson regressions were applied for statistical analysis. Compared to the statewide risk, the risks of ASD, VSD, and PDA in four selected counties with high HF activities were significantly higher. The Annual Natural Gas Production from HF was significantly correlated with risks of ASD, PDA, MIC, and total birth defect after adjusting for counties and years. No significant associations of HF activities were found with VSD and HSB. This ecological study suggested that hydraulic fracturing might be associated with the increased risk of some birth defects in the Barnett Shale Region, TX, which warrants further investigations due to the limitation of an ecological study design.