An association between the heat-humidity index and preterm labor and delivery: A preliminary analysis

Objectives: The goal of this study was to determine whether a relationship exists between heat-humidity indexes and rates of preterm labor and preterm delivery. Methods: Preterm labor and delivery rates were compared during the 2 summer and 2 winter weeks with the highest and lowest heat- humidity indexes for each season. Results: The rate of preterm labor increased consistently from 1.23% to 3.00% as the heat-humidity index rose. When preterm births were examined, the trend was similar but not statistically significant. Conclusions: Given the public health import of preterm labor and the frequency with which pregnant women may be exposed to extremes of heat, studies designed to confirm or refute our preliminary observations are warranted.