Reduced urinary aldosterone in preeclampsia, superimposed pre-eclampsia compared to standard- and high-risk pregnant women

Background:

Women with chronic kidney disease (CKD) and chronic hypertension (CHT) are at increased risk of superimposed pre-eclampsia (SPE) and associated adverse pregnancy outcomes. Diagnosis of SPE using blood pressure and proteinuria is of limited use because they may develop in women with CKD or CHT without the condition. Inaccurate diagnosis may result in unnecessary iatrogenic preterm delivery. In established pre-clampsia (PE), aldosterone levels are supressed. The aim of the study was to compare the urinary aldosterone concentrations between normotensive controls (NC), PE and CKD/CHT women with and without SPE at term.

Methods:

NC women (n = 25), women with PE (n = 22), CKD or CHT (n = 25) and SPE (n = 21) were recruited from two tertiary antenatal clinics at term (mean ± SD 38 ± 3 weeks'). Diagnoses of PE and SPE were according to the International Society of the Study of Hypertension in Pregnancy guidelines. Urinary tetrahydroaldosterone was measured by gas chromatography-mass spectrometry (GC-MS); creatinine was measured using a standard clinical laboratory assay for normalisation.

Results:

A Kruskal Wallis test indicated significant differences between groups (P < 0.0001). Aldosterone concentrations were significantly lower in both PE and SPE compared to the NC and CKD/CHT women (median [IQR], PE: 6.45 [2.95, 14.37]; SPE: 10.82 [5.42, 16.44]; NC: 13.75 [9.07, 29.80]; CKD/CHT: 24.18 [16.29, 37.88] µg/mmol creatinine; P < 0.05 for all).

Conclusions:

The lower aldosterone in SPE is similar to that found in pre-eclampsia, suggesting similar aetiologies. This finding has substantial implications for the future antenatal management of these women and their offspring. Further exploration of the aetiological and predictive value of aldosterone for adverse pregnancy events in women with CKD and/or CHT and its role in cases of diagnostic uncertainty is required.