Impact of BMI on Serum Magnesium Levels in Pregnant Women Undergoing Magnesium Sulphate Therapy for Seizure Prophylaxis

Maternal mortality from severe preeclampsia and eclampsia have drastically declined in developed nations due to the effective use of magnesium sulphate. However, these rates remain high in developing countries, including India. Various factors, such as body mass index (BMI) may influence serum magnesium levels in patients undergoing prophylactic and therapeutic treatment with the Pritchard regimen. The current study aimed to evaluate how BMI affects serum magnesium levels in patients receiving magnesium sulphate therapy for seizure prophylaxis.

The researchers conducted the study from June 2021 to July 2022 and enrolled 160 patients with severe preeclampsia and eclampsia treated with the Pritchard regimen. Serum magnesium levels were calculated after the loading dose, the third dose, and 24 hours after the last dose. Patients were categorized according to WHO BMI classifications.

The results showed the following findings:

• After the loading dose, average serum magnesium levels varied by BMI: patients with BMI < 18.5 had 3.91 ± 1.09 mg/dl, those with BMI 18.5-24.99 had 3.42 ± 0.97 mg/dl, those with BMI 25-29.99 had 3.20 ± 0.81 mg/dl, and those with BMI ≥ 30 had 2.77 ± 0.67 mg/dl. 
• While the p-value (0.0616) was not statistically significant, a trend of reducing serum magnesium with increasing BMI was observed. 
• After the third dose, the average serum magnesium levels for the BMI groups were 6.76 ± 0.95 mg/dl, 6.34 ± 1.15 mg/dl, 5.83 ± 1.02 mg/dl, and 5.58 ± 1.00 mg/dl, respectively, with a statistically significant difference (p=0.0001). Additionally, the convulsion rate was higher among obese patients (13.04%) compared to non-obese patients (2.91%).
• After 3rd dose mean serum magnesium of patients with BMI < 18.5, 18.5-24.99, 25-29.99 and ≥30 was 6.76 ± 0.95 mg/dl, 6.34±1.15 mg/dl, 5.83±1.02 mg/dl and 5.58 ± 1.00 mg/dl respectively and the difference was statistically significant.
• Convulsion rate was higher in obese patient (13.04%) compared to non-obese (2.91%). 

The study concluded that BMI significantly impacts serum magnesium levels in pregnant women receiving magnesium sulphate therapy for seizure prophylaxis.

Source: Ahmed NI, Taye MK, Teron L, Ahmed M. Effect of BMI on serum magnesium level in patient getting Pritchard regimen. The New Indian Journal of OBGYN. 10(2):257-261.doi: 10.21276/obgyn.2024.10.2.4.