There is a dearth of information on the patterns of electrolyte derangements among perioperative women with obstructed labour. We measured the levels and patterns of electrolyte derangements among women with obstructed labour in eastern Uganda. This was a secondary analysis of data for 389 patients with obstructed labour, diagnosed by either an obstetrician or medical officer on duty between July 2018 and June 2019. Five milliliters of venous blood was drawn from the antecubital fossa under an aseptic procedure for electrolytes and complete blood analyses. The primary outcome was the prevalence of electrolyte derangements, defined as values outside the normal ranges: Potassium 3.3–5.1 mmol/L, Sodium 130–148 mmol/L, Chloride 97–109 mmol/L, Magnesium 0.55–1.10 mmol/L, Calcium (Total) 2.05–2.42 mmol/L, and Bicarbonate 20–24 mmol/L. The most prevalent electrolyte derangement was hypobicarbonatemia [85.8% (334/389)], followed by hypocalcaemia [29.1% (113/389)], then hyponatremia [18% (70/389)]. Hyperchloraemia [4.1% (16/389)], hyperbicarbonatemia [3.1% (12/389)], hypercalcaemia [2.8% (11/389)] and hypermagnesemia [2.8% (11/389)] were seen in a minority of the study participants. A total of 209/389 (53.7%) of the participants had multiple electrolyte derangements. Women who used herbal medicines had 1.6 times the odds of having multiple electrolyte derangements as those who did not use herbal medicines [Adjusted Odds Ratio (AOR): 1.6; 95% Confidence Interval (CI): (1.0–2.5)]. Having multiple electrolyte derangements was associated with perinatal death although this estimate was not precise [AOR 2.1; 95% CI: (0.9–4.7)]. Women with obstructed labour in the perioperative period have multiple electrolyte derangements. Use of herbal medicines in labour was associated with having multiple electrolyte derangements. We recommend routine assessment of electrolytes prior to surgery in patients with obstructed labour.