Acute Associations Between Outdoor Temperature and Premature Rupture of Membranes.

Background: Extreme ambient temperatures have been linked to preterm birth. Preterm premature rupture of membranes is a common precursor to preterm birth but is rarely studied in relation to temperature. Methods: We linked 15,381 singleton pregnancies with premature rupture of membranes from a nationwide US obstetrics cohort (2002-2008) to local temperature. Case-crossover analyses compared daily temperature during the week preceding delivery and the day of delivery to 2 control periods, before and after the case period. Conditional logistic regression models calculated the odds ratio (OR) and 95% confidence intervals (CIs) of preterm and term premature rupture of membranes for a 1 degrees C increase in temperature during the warm (May-September) and cold (October-April) season separately after adjusting for humidity, barometric pressure, ozone, and particulate matter. Results: During the warm season, 1 degrees C increase during the week before delivery was associated with a 5% (95% CI, 3%, 6%) increased preterm premature rupture of membranes risk, and a 4% (95% CI, 3%, 5%) increased term premature rupture of membranes risk. During the cold season, 1 degrees C increase was associated with a 2% decreased risk for both preterm (95% CI, 1%, 3%) and term premature rupture of membranes (95% CI, 1%, 3%). The day-specific associations for the week before delivery were similar, but somewhat stronger for days closer to delivery. Conclusions: Relatively small ambient temperature changes were associated with the risk of both preterm and term premature of membranes. Given the adverse consequences of premature rupture of membranes and concerns over global climate change, these findings merit further investigation. See video abstract at, http://links.lww.com/EDE/B312.