Sodium intake and the development of hypertensive disorders of pregnancy

Abstract

In non-pregnant populations, sodium intake has been associated with the development of chronic hypertension, and sodium restriction has been identified as a strategy to reduce blood pressure. Data regarding the relationship between sodium intake and development of hypertensive disorders of pregnancy are limited and conflicting. To assess the association between daily periconceptional sodium intake and risk of hypertensive disorders of pregnancy. This was a secondary analysis of the prospective Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be study. In this analysis, we included participants with non-anomalous, singleton pregnancies who completed food frequency questionnaires with recorded sodium intake in the 3 months prior to pregnancy. Individuals whose pregnancies did not progress beyond 20 weeks of gestation were excluded. Sodium intake was categorized as low (<2g per day), medium (2g to <3g per day), or high (≥ 3g per day), based on thresholds used in the non-pregnant population. The primary outcome was development of a new-onset hypertensive disorder of pregnancy, including gestational hypertension, preeclampsia, hemolysis, elevated liver enzymes, and low platelet count syndrome (HELLP), superimposed preeclampsia, or eclampsia. Bivariable analyses were performed using Kruskal-Wallis and Chi square tests. Poisson regression was used to estimate adjusted incidence risk ratios (aIRR) with 95% confidence intervals (CIs) after controlling for potentially confounding factors. Among 7,458 individuals included in this analysis, 2,336 (31%) reported low sodium intake, 2,792 (37%) medium sodium intake, and 2,330 (31%) high sodium intake. Individuals with high sodium intake were more likely to have chronic hypertension, use tobacco, and to be living with obesity. The risk of developing a hypertensive disorder of pregnancy was similar among groups (medium vs. low aIRR 1.10, 95% CI 0.94-1.28; high vs. low aIRR 1.17, 95% CI 1.00-1.37). There were no differences in neonatal outcomes by sodium intake, including preterm birth, small-for-gestational-age neonate, and admission to the neonatal intensive care unit. Sodium intake was not associated with risk of developing a hypertensive disorder of pregnancy. This lack of association contrasts with that between sodium intake and hypertension in the non-pregnant state, and may reflect differences in the pathophysiology underlying pregnancy- versus non-pregnancy-related hypertensive disorders.