The relation of gestation length to short-term heat stress.

OBJECTIVES: This study examined the association between gestation length and heat exposure during the summer months of the Chicago heat wave of 1995. METHODS: Birth data from Illinois vital records containing 11,792 singleton vaginal births were analyzed to calculate mean gestational ages. RESULTS: No evidence was found to suggest an association between shortened gestation and increased maximum apparent temperature. CONCLUSIONS: The data propose no special precautions for pregnant women exposed to short-term heat stress of the intensity evaluated in this study. However, the possible effects of chronic heat exposure on gestation cannot be ruled out.