Normal-range urinary albumin excretion associates with blood pressure and renal electrolyte handling in pregnancy

Abstract

Albuminuria in the pathological range is a significant predictor of preeclampsia. In healthy persons, high normal urinary albumin predicts a later incidence of hypertension and is associated with salt sensitivity of blood pressure. We hypothesized that in pregnancy urinary albumin in the normal range associates with blood pressure through activation of distal Na+ reabsorption and renal salt retention by plasma factors cofiltered with albumin. We analyzed 24-h urine collections and plasma samples from gestational week 29 of 560 pregnant women from the Odense Child Cohort, a Danish population-based cohort. Plasma and urinary aldosterone were measured by ELISA. Plasma and urinary Na+, K+, Cl−, and creatinine were also determined. Predictive values of urinary albumin were assessed by linear mixed, multiple, and Cox regression analyses. Primary outcomes were blood pressure and renal electrolyte handling. Twenty-four-hour urinary albumin excretion at gestational week 29 associated with gestational blood pressure trajectory, with adjusted β coefficients (95% confidence intervals) for each 10-fold increase in urinary albumin as follows: 5.71 (1.60 to 9.81) mmHg for systolic blood pressure and 4.39 (1.41 to 7.38) mmHg for diastolic blood pressure. Urinary albumin was inversely associated with fractional excretion rates of Na+, K+, and Cl−, with adjusted β coefficients (95% confidence intervals) for each 10-fold increase in urine albumin as follows: −0.25 (−0.35 to −0.14), −5.06 (−6.81 to −3.30), and −0.28 (−0.41 to −0.15), respectively. In conclusion, at gestational week 29, urinary albumin excretion in the normal range associated with blood pressure and renal electrolyte handling independent of potential confounders.