Ambient temperature and preterm birth: Interaction by maternal medical factors and medications

BACKGROUND: Associations between high temperatures and preterm birth (PTB) were reported. However, characteristics of vulnerable pregnancies are unknown. We aimed to examine pre-pregnancy comorbidities, PTB history, and prescribed medications during pregnancy as potential modifiers. METHODS: We conducted a secondary analysis of a historical cohort of 131 599 births in Southern Israel in 2005-2019. Maternal address and a spatiotemporal model were used to assess weekly average temperatures. We employed a Cox model with time-dependent covariates using a distributed lag non-linear model, adjusted for ethnicity, socioeconomic status, and time-varying seasonality. Associations were stratified by PTB history and restricted by comorbidities and medications. P-values for interaction were from likelihood ratio tests of models with multiplicative interaction term. Corrections for multiple comparisons were done using the Holm-Bonferroni method. RESULTS: Associations differed by PTB history (p for interaction