What are the benefits of magnesium sulfate in the management of pregnancy?

From the Guidelines

Magnesium sulfate is a crucial medication in the management of pregnancy, particularly for preventing eclampsia in women with preeclampsia, and its use is strongly recommended by recent guidelines. The most recent and highest quality study, published in 2022 1, suggests that magnesium sulfate should be administered antenatally to women with severe pre-eclampsia and at least one clinical sign of seriousness to reduce the risk of eclampsia, with a strong agreement (GRADE 1+).

Key Points

• Magnesium sulfate prevents eclampsia, approximately halving the rate, with approximately 100 women needing treatment to prevent 1 seizure 1.
• The International Society for the Study of Hypertension in Pregnancy (ISSHP) recommends that all preeclamptic women in low- and middle-income countries (LMICs) should receive magnesium sulfate due to the significant cost-benefit ratio 1.
• In highly specialized centers and high-income settings, selective use in women with preeclampsia is reasonable, considering the costs of administering magnesium sulfate 1.
• The dosing regimens used in the Eclampsia and MAGPIE trials should be followed, which typically include a 4-6 gram IV loading dose over 15-20 minutes, followed by a maintenance infusion of 1-2 grams per hour, continuing for 24 hours after delivery or the last seizure.
• During administration, patients require monitoring of vital signs, deep tendon reflexes, respiratory rate, and urine output, with magnesium levels checked periodically to aim for therapeutic ranges of 4-7 mEq/L 1.
• Calcium gluconate (1 gram IV) should be available as an antidote for magnesium toxicity.
• Common side effects include flushing, sweating, and injection site pain, while serious adverse effects may include respiratory depression and cardiac arrest at toxic levels.

From the FDA Drug Label

In Pre-eclampsia or Eclampsia In severe pre-eclampsia or eclampsia, the total initial dose is 10 to 14 g of magnesium sulfate. Continuous administration of magnesium sulfate beyond 5 to 7 days to pregnant women can lead to hypocalcemia and bone abnormalities in the developing fetus. Magnesium sulfate should be used during pregnancy only if clearly needed.

The benefits of magnesium sulfate in management for pregnancy include its use in severe pre-eclampsia or eclampsia. However, it should be used with caution and only if clearly needed, as continuous administration beyond 5 to 7 days can cause fetal abnormalities 2 2. Key benefits include:

• Control of seizures in severe pre-eclampsia or eclampsia
• Initial dose of 10 to 14 g of magnesium sulfate However, important considerations include:
• Use only if clearly needed
• Avoid continuous administration beyond 5 to 7 days to prevent fetal harm
• Monitor for signs of magnesium intoxication, especially in the presence of renal insufficiency

From the Research

Benefits of Magnesium Sulfate in Pregnancy Management

• Magnesium sulfate is the drug of choice for women with eclampsia, as it reduces the risk of recurrence of seizures and probably reduces maternal death 3, 4, 5.
• Magnesium sulfate more than halves the risk of eclampsia in women with pre-eclampsia, with a non-significant reduction in maternal death and no clear difference in serious maternal morbidity 4.
• The use of magnesium sulfate is associated with a reduction in placental abruption and an increase in caesarean section, but no clear difference in stillbirth or neonatal death 4.
• Magnesium sulfate reduces the risk of maternal death and recurrence of seizures compared to diazepam, with no clear differences in other measures of maternal morbidity 5.
• Magnesium sulfate has a favorable effect on neonatal outcomes, including a reduction in the risk of admission to a special care baby unit and a decrease in the length of stay in the special care baby unit 3, 5.

Side Effects and Safety

• Side effects of magnesium sulfate are common, with approximately a quarter of women reporting side effects such as flushing 4.
• Magnesium sulfate can be used safely in severe preeclampsia, with a low risk of severe complications and major side effects, provided a rigorous protocol is followed 6.
• Magnesium sulfate does not significantly affect labor outcomes, including oxytocin stimulation, admission-to-delivery intervals, prolonged second-stage labor, forceps delivery, and cesarean delivery, compared to phenytoin 7.

Comparison with Other Anticonvulsants

• Magnesium sulfate is more effective than phenytoin in reducing the risk of recurrence of seizures and probably reducing maternal death 3.
• Magnesium sulfate is more effective than diazepam in reducing the risk of maternal death and recurrence of seizures 5.
• Magnesium sulfate is more effective than nimodipine in reducing the risk of eclampsia 4.