Drilling and Production Activity Related to Unconventional Gas Development and Severity of Preterm Birth

BACKGROUND: Studies of unconventional gas development (UGD) and preterm birth (PTB) have not presented risk estimates by well development phase or trimester. OBJECTIVE: We examined phase and trimester-specific associations between UGD activity and PTB. METHODS: We conducted a case–control study of women with singleton births in the Barnett Shale area, Texas, from 30 November 2010 to 29 November 2012. We individually age- and race/ethnicity-matched five controls to each PTB case ([Formula: see text]) and truncated controls’ time at risk according to the matched case’s gestational age. We created phase-specific UGD-activity metrics: a) inverse squared distance–weighted (IDW) count of wells in the drilling phase [Formula: see text] (804.7 meters) of the residence and b) IDW sum of natural gas produced [Formula: see text] of the residence. We also constructed trimester- and gestation-specific metrics. Metrics were categorized as follows: zero wells (reference), first, second, third tertiles of UGD activity. Analyses were repeated by PTB severity: extreme, very, and moderate ([Formula: see text] , [Formula: see text] , and [Formula: see text] completed weeks). Data were analyzed using conditional logistic regression. RESULTS: We found increased odds of PTB in the third tertile of the UGD drilling {[Formula: see text] [95% confidence interval (CI): 1.06, 1.37]} and UGD-production [[Formula: see text] (1.05, 1.26)] metrics. Among women in the third tertile of UGD-production, associations were strongest in trimesters one [[Formula: see text] (1.02, 1.37)] and two [[Formula: see text] (0.99, 1.31). The greatest risk was observed for extremely PTB [third tertile ORs: UGD drilling, 2.00 (1.23, 3.24); UGD production, 1.53 (1.03–2.27)]. CONCLUSIONS: We found evidence of differences in phase- and trimester-specific associations of UGD and PTB and indication of particular risk associated with extremely preterm birth. Future studies should focus on quantifying specific chemical and nonchemical stressors associated with UGD. https://doi.org/10.1289/EHP2622