Objective: To quantify the short-term effects of maternal exposure to heatwave on preterm birth.
Design: An ecological study.
Setting: A population-based study in Brisbane, Australia.
Population: All pregnant women who had a spontaneous singleton live birth in Brisbane between November and March in 2000-2010 were studied.
Methods: Daily data on pregnancy outcomes, meteorological factors, and ambient air pollutants were obtained. The Cox proportional hazards regression model with time-dependent variables was used to examine the short-term impact of heatwave on preterm birth. A series of cut-off temperatures and durations were used to define heatwave. Multivariable analyses were also performed to adjust for socio-economic factors, demographic factors, meteorological factors, and ambient air pollutants.
Main outcome measure: Spontaneous preterm births.
Results: The adjusted hazard ratios (HRs) ranged from 1.13 (95% CI 1.03-1.24) to 2.00 (95% CI 1.37-2.91) by using different heatwave definitions, after controlling for demographic, socio-economic, and meteorological factors, and air pollutants.
Conclusions: Heatwave was significantly associated with preterm birth: the associations were robust to the definitions of heatwave. The threshold temperatures, instead of duration, could be more likely to influence the evaluation of birth-related heatwaves. The findings of this study may have significant public health implications as climate change progresses.
Keywords: Hazards ratio; heatwave; preterm birth; survival analysis.
© 2013 RCOG.