Comparative Study of Plasma Electrolyte Status in Pre-eclamptic and Normotensive Pregnant Women in Zaria.

Background: Pre-eclampsia is a major cause of maternal and perinatal morbidity, characterized by endothelial dysfunction and renal impairment that may alter electrolyte balance. However, findings on electrolyte disturbances remain inconsistent, and the absence of population-specific reference intervals limits clinical interpretation in low-resource settings. Objective: To evaluate plasma electrolyte patterns among pre-eclamptic and normotensive pregnant women and establish locally relevant reference intervals for electrolyte parameters in Zaria, Nigeria. Methods: A comparative cross-sectional study was conducted at Ahmadu Bello University Teaching Hospital, Zaria, from January to August 2024. A total of 222 pregnant women were enrolled, comprising 100 women with pre-eclampsia and 122 normotensive controls. Plasma sodium, potassium, chloride, and bicarbonate concentrations were measured using an ion-selective electrode analyzer. Independent t-tests and chi-square tests were used for group comparisons, while multivariable linear and logistic regression analyses adjusted for gestational age. Reference intervals were derived from the normotensive cohort. Results: Mean concentrations of sodium, potassium, chloride, and bicarbonate did not differ significantly between groups (all p > 0.05). However, hyponatraemia was significantly more prevalent among women with pre-eclampsia than controls (44.0% vs. 27.9%) and remained independently associated with pre-eclampsia after adjustment for gestational age (adjusted OR 3.54, 95% CI 1.75-7.17; p < 0.001). No significant differences were observed in potassium, chloride, or bicarbonate abnormalities. Reduced bicarbonate levels in both groups were consistent with physiological renal compensation for pregnancy-related respiratory alkalosis. Locally derived reference intervals showed modest differences from conventional ranges. Conclusion: Electrolyte disturbances in pre-eclampsia are better reflected by distributional abnormalities than by differences in mean concentrations. The strong association between hyponatraemia and pre-eclampsia highlights its potential clinical relevance and underscores the need for context-specific reference intervals and prospective studies to determine its temporal and prognostic significance.