Extreme Heat and Preterm Birth Risk—Methodologic Considerations and Policy Implications

In this issue of JAMA Pediatrics, Ye et al report an analysis of more than 1 million births in the Greater Sydney region of New South Wales, Australia, revealing a significant association between extreme heat exposure in the third trimester and preterm birth (PTB). Individuals experiencing temperatures over the 95th percentile for their residential location during their third trimester had 61% higher odds of PTB (adjusted odds ratio [OR], 1.61; 95% CI, 1.55-1.67). There was no significant association of extreme heat in the other 2 trimesters with PTB. Ye and colleagues also observed significant interaction between heat and greenness on the outcome of PTB; individuals with extreme heat exposure had lower odds of preterm birth if they resided in greener areas (interaction P < .05). We commend the authors’ study and its important implications. As the world’s temperatures increase, it is critical not just to document health impacts but to identify targets of intervention, such as greening, that promise to mitigate some of the negative effects of climate change.