Multicentre evidence for an independent association between third-trimester hypoaldosteronism and preeclampsia.

The study aimed to investigate the association of plasma aldosterone concentration (PAC) on admission before delivery with preeclampsia, admission blood pressure, and pregnancy outcomes. In this multicenter observational study (May 2023-December 2024), 886 pregnancies (125 preeclampsia, 761 controls) from six hospitals were analyzed. Associations were evaluated using multivariable logistic regression, Spearman's correlation, and restricted cubic spline models, with sensitivity analysis employing Winsorization. Piecewise regression was employed to identify breakpoint and examine threshold effect. Preeclamptic women had significantly lower PAC than controls (16.73 [11.03, 32.59] vs. 28.16 [15.99, 52.82] ng/dL, P < 0.001). Lower PAC was independently associated with preeclampsia (adjusted OR: 0.98; 95% CI 0.98-0.99; P < 0.001) and correlated with higher systolic blood pressure (ρ = -0.170, P < 0.001) and adverse outcomes (P < 0.05). A significant nonlinear relationship was observed (P < 0.001), with a breakpoint at 11.74 ng/dL where each 1-unit increase reduced preeclampsia odds by 30% below it (adjusted OR 0.70; 0.57-0.87) and only by 2% at or above it (adjusted OR 0.98; 0.97-0.99). Lower PAC showed an independent, nonlinear association with preeclampsia, characterized by a threshold effect around 11.74 ng/dL, and is linked to elevated systolic blood pressure and adverse maternal-fetal outcomes.