Background: There are many risk factors of development of preeclampsia among the pregnant women. Objective: The purpose of the present study has set out to assess the relationship between preeclampsia and blood ionized magnesium levels.
 Methodology: This case-control study was performed in the Department of Obstetrics and Gynaecology, Dhaka Medical College and Hospital from January 2020 to December 2021 for a period of 2(two) years. Pregnant patients who showed preeclampsia were all the amounts of ionized magnesium in venous blood collected from patients with preeclampsia. Additionally, the magnesium levels of age-matched, healthy pregnant women were determined.
 Results: A total number of 100 pregant women included in this study of which 50 pregnant women were designated as case and the rest 50 pregnant women were control. It has found that serum levels of ionized magnesium were significantly decreased among preeclamptic cases (0.58 ± 0.06) as compared to normal pregnancies (0.72 ± 0.05) (p < 0.001). Using a cut-off value of 0.7 mmol/l, the serum ionized magnesium level was divided into two groups and was compared between cases and controls. The risk of developing preeclampsia was more than 33 (95% CI = 10.9 – 102.1) times higher in pregnant women with serum magnesium level < 0.7 mmol/L than those pregnant women with serum magnesium level 0.7 or > 0.7 mmol/L.
 Conclusion: Low level of serum ionized magnesium is a risk factor of development of preeclampsia.