Effects of Ambient Temperature During Pregnancy on Newborn Birthweight.

This study evaluates the association between ambient temperature exposure during pregnancy and newborn birthweight, using a penalized generalized additive model (GAM) framework with distributed lag non-linear models (DLNM) to identify sensitive windows of exposure. The analysis includes 238 participants from the SHIP study with complete temperature exposure and birthweight data. Weekly maximum temperatures during pregnancy were estimated using Daymet data, and the impact of temperature on birthweight was assessed, adjusting for maternal age, pre-pregnancy BMI, gestational age, race, smoking, diabetes status, and infant biological sex. The model incorporated a crossbasis function for temperature exposure across 42 gestational weeks and allowed penalization for smoother, data-driven lag estimation. Results from the combined-sex model indicated that higher ambient temperatures during the third trimester, particularly in the final weeks of pregnancy, were associated with increased birthweight. Stratified analyses suggested that this association was more pronounced in male infants. These findings highlight the importance of considering prenatal temperature exposures and timing when evaluating determinants of newborn health.