Dietary sodium, potassium, and blood pressure in normotensive pregnant women: the National Health and Nutrition Examination Survey

Abstract

Dietary sodium, potassium, and sodium-to-potassium ratio are linearly associated with blood pressure in nonpregnant adults. Earlier investigations suggested null or inverse associations of blood pressure and sodium during normotensive pregnancy; findings have not been confirmed in race/ethnically diverse women or while accounting for potassium. Our purpose was to evaluate associations of blood pressure with sodium and potassium and sodium-to-potassium ratio in race/ethnically diverse normotensive pregnant women. We used cross-sectional blood pressure and dietary data from 984 women in multiple cycles of the National Health and Nutrition Examination Survey (mean age = 27.6 ± 0.2 years). We tested for differences in blood pressure across quartiles of sodium intake using Kruskal–Wallis tests and linear regression to evaluate associations of sodium, potassium, and the sodium-to-potassium ratio with systolic (SBP) and diastolic (DBP) blood pressures. We adjusted for potential confounding variables: age, race/ethnicity, education, marital status, body mass index, smoking, and month of pregnancy. SBP and DBP were similar across quartiles of sodium intake: quartile 1 (lowest sodium intake): 107/59; quartile 2: 106/59; quartile 3: 108/60; quartile 4 (highest sodium intake): 108/58 mm Hg, p > 0.60 for all. Sodium (β = 0.16, 95% confidence interval (CI): –0.20 to 0.52) and potassium (β = 0.18, 95% CI: –0.24 to 0.60) and the sodium-to-potassium ratio (β = –0.54, 95% CI: –1.55 to 0.47) were not associated with SBP or DBP. Results were similar in stratified analyses. Novelty Blood pressure was similar among quartiles of sodium or potassium intake, even in analyses stratified by race/ethnicity and trimester of pregnancy. There was no association of sodium or potassium with blood pressure. Blood pressure may be insensitive to dietary sodium and potassium during normotensive pregnancy.