Correlations of spot urinary sodium and potassium with blood pressure in pregnant women: A longitudinal study in Southern Thailand

Abstract

To assess the changes of spot urinary sodium and potassium and blood pressure (BP) throughout pregnancy and their correlations in southern Thailand. A longitudinal study was conducted in southern Thailand from March 2018 to November 2019. Spot urinary excretion of sodium per creatinine (U[Na+ ]/[Cr]), potassium per creatinine (U[K+ ]/[Cr]) and U[Na+ ]/[K+ ] ratios, and BP were measured at four time points throughout pregnancy. A one-way analysis of variance with repeated measures and Bonferroni correction with post hoc analysis was used to identify significant differences between time points. The correlations were measured using Pearson's correlation coefficients. A total of 327 pregnant women were included. Both systolic and diastolic BPs decreased gradually from up to 14weeks of pregnancy to 18-22weeks and then increased until 30-34weeks. Mean spot U[Na+ ]/[Cr] ratios did not significantly change during the study period. Mean spot U[K+ ]/[Cr] ratios gradually increased, and spot U[Na+ ]/[K+ ] ratios gradually decreased. The correlation of spot U[Na+ ]/[Cr] and U[K+ ]/[Cr] ratios with BPs was weakly negative at all four time points. Spot U[Na+ ]/[Cr] and U[K+ ]/[Cr] ratios are inversely correlated with BPs; weak correlations are found among pregnant women in southern Thailand. Further research in different populations is required to confirm its correlation and broader use.