ObjectiveTo determine associations of maternal salivary aldosterone with blood pressure (BP) in pregnancy and infant birth weight-for-gestational age (BWGA).MethodsWe measured maternal salivary aldosterone, BP and BWGA z-scores in 471 Mexico City pregnancy cohort participants and performed multivariable linear regression of BP and BWGA on log-aldosterone levels.ResultsLog-aldosterone was positively associated with diastolic BP (beta = 0.12 95% CI: 0.04, 0.21). There were no main effects of log-aldosterone on BWGA. However, we detected an interaction between log-aldosterone and BP in association with BWGA; higher log-aldosterone was associated with lower BWGA in the lowest (beta = -0.12, 95% CI: -0.26, 0.02) and highest (beta = -0.12, 95% CI: -0.29, 0.06) BP tertiles. In contrast, in the middle BP tertile the association was positive (beta = 0.09, 95% CI: -0.02, 0.20), p for interaction = 0.03.ConclusionHigher maternal salivary aldosterone is positively associated with diastolic BP and may affect fetal growth differently depending on concurrent maternal blood pressure.