Objective:To determine the serum calcium-magnesium ratio in pre-eclampsia and compare with normotensives. Methods:A case-control study was conducted in a tertiary hospital between October 2017 and March 2018 among 81 pregnant women (27 cases and 54 controls matched for age, gestational age, and parity). An interviewer-administered questionnaire was used to obtain data on demography/clinical history. Venous blood was collected without stasis and sent for biochemical analysis. Statistical analysis used IBM SPSS 21.0. Results: The levels of serum Ca 2+ (7.73 + 1.24 vs 9.17 + 0.77; P<0.001), Ca 2+ -Mg 2+ ratio (3.36 + 0.60 vs 3.83 + 0.41; P=0.001), and Mg 2+ (2.35 + 0.35 vs 2.41 + 0.16; P=0.469) were lower among cases. Serum Ca 2+ level correlated negatively with systolic (r=0.45, P=0.05) and diastolic blood pressure (r=0.50, P=0.010) among the cases. Hypocalcemia was a risk factor (adjusted odds ratio [AOR] 7.63, 95% confidence interval [CI] 1.64-35.37) while social classes 2 and 3 were protective factors (AOR 0.01, 95% CI 0.00-0.46 and AOR 0.01, 95% CI 0.00-0.24, respectively) against pre-eclampsia. Conclusion:The result of this research supported the implication of micronutrients in pre-eclampsia and may help to understand the pathophysiological process of pre-eclampsia. It will also help to establish and enhance existing preventive strategies for the condition. The recommendation by WHO on calcium supplementation in pregnancy as a step in preventing the occurrence of pre-eclampsia should be practiced.