Exposure to medication was defined as self-reported use at least once during the month before conception through the end of the first trimester. # Referred to the participants unexposed to EHE90 and adjusted for maternal age (continuous), maternal race/ethnicity, and maternal education level. NC* indicated estimates for case groups with <3 exposed cases were not calculated. PInt indicated P value for EHE90*medication use. Abbreviationsa OR, adjusted odds ratio; AR, Arkansas; CA, California; CHD, congenital heart defects; CI, confidence interval; EHE, extreme heat event; EHE90, EHE was defined using the 90th percentile of daily maximum temperature for each study region during postconceptional weeks 3–8; GA, Georgia; IA, Iowa; ICR, interaction contrast ratio; NBDPS, National Birth Defects Prevention Study; NC, North Carolina; NY, New York; TX, Texas; UT, Utah.