LAUSR

In 2014, the Hazelwood coal mine fire was an unprecedented six-week severe smoke event in the Latrobe Valley, southeastern Australia. We aimed to determine whether maternal exposure to fine particulate matter (PM2.5) attributable to coal mine fire smoke was associated with gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy and abnormal placentation. We defined a cohort of all births >20 weeks in the Latrobe Valley from 1 March 2012 - 31 Dec 2015 utilising administrative perinatal data. Average and peak PM2.5 was assigned to residential address at delivery using a chemical transport model. Maternal, meteorological and temporal variables were included in final log-binomial regression models. 3,612 singleton pregnancies were included; 766 were exposed to the smoke event. Average maternal PM2.5 exposure was 4.4 µg/m3 (IQR 2.1). Average peak PM2.5 exposure was 44.9 µg/m3 (IQR 35.0). An interquartile range increase in average and peak PM2.5 was associated with a 7% and 16% increased likelihood of GDM respectively (Average PM2.5 95%CI 1.03, 1.10; <0.0001; Peak PM2.5 95%CI 1.09, 1.22; <0.0001). No association for hypertensive disorders or abnormal placentation was observed. This is the first study to examine obstetric complications relating to a discrete smoke event. These findings may guide the public health response to future similar events. Exposure to a smoke event was associated with an increased risk of GDM. The public health implications may be substantial with a changing climate.