What is the role of magnesium supplementation during pregnancy?

From the Guidelines

Magnesium supplements, specifically MgSO4, should be administered to all preeclamptic women in low- and middle-income countries (LMICs) to prevent eclampsia, as the cost-benefit is greatest in these settings. According to the International Society for the Study of Hypertension in Pregnancy (ISSHP) recommendations, as stated in the 2018 study published in Hypertension 1, MgSO4 can approximately halve the rate of eclampsia, with approximately 100 women needing MgSO4 to prevent 1 seizure.

Key Considerations

• The ISSHP recommends that each unit has a consistent policy on the use of MgSO4, incorporating appropriate monitoring, recognition of the risks of MgSO4 infusions, and assessment of maternal and fetal outcomes.
• The dosing regimens used in the Eclampsia and MAGPIE trials should be used, as stated in the ISSHP recommendations 1.
• In highly specialized centers and high-income settings, selective use of MgSO4 in women with preeclampsia is reasonable, considering the higher costs of administration.

Administration and Monitoring

• MgSO4 should be administered to women with preeclampsia who have severe hypertension and at least 3+ of proteinuria or slightly lower measurements (150/100 mm Hg and at least 2+ of proteinuria) in the presence of at least 2 signs or symptoms of imminent eclampsia.
• Pregnant women should be closely monitored for potential side effects and interactions with other medications when taking magnesium supplements.

Importance of Magnesium During Pregnancy

• Magnesium is essential during pregnancy for preventing complications such as preeclampsia, premature labor, and muscle cramps, while also supporting fetal development, particularly of the skeletal and nervous systems.
• Pregnant women should consult their healthcare provider before starting any supplement, as individual needs vary and excessive magnesium can cause digestive issues or interact with certain medications.

From the FDA Drug Label

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. Continuous use of magnesium sulfate in pregnancy beyond 5 to 7 days can cause fetal abnormalities.

The use of magnesium sulfate as a supplement in pregnancy should be approached with caution. Magnesium sulfate should only be used if clearly needed, and its use beyond 5 to 7 days can cause fetal abnormalities, including hypocalcemia and bone abnormalities. Key considerations include:

• Duration of treatment: The shortest duration of treatment that can lead to fetal harm is not known.
• Fetal risk: Continuous administration beyond 5 to 7 days can lead to fetal abnormalities.
• Need for use: Magnesium sulfate should only be used during pregnancy if clearly needed 2.

From the Research

Magnesium Supplement for Pregnancy

• Magnesium supplements are commonly used in pregnancy to treat preterm labor and preeclampsia 3, 4, 5, 6
• The use of magnesium sulfate as a treatment for preterm labor and preeclampsia has been studied extensively, with varying results 3, 4, 5, 6
• One study found that the measurement of total magnesium may not be adequate for the titration of therapeutic magnesium infusions in patients with preeclampsia or preterm labor, due to the lack of correlation between total magnesium and the physiologically active ionized magnesium 3
• Another study found that a 4 g loading dose of magnesium sulfate is usually adequate to achieve therapeutic levels in preeclampsia, but not in preterm labor 4
• A study published in 2014 found that basal magnesium levels in preterm labor had a predictive value in evaluating magnesium tocolysis response, and may help to select patients who are appropriate for magnesium tocolysis 5
• A Cochrane review found that there is not enough evidence to show any difference between magnesium maintenance therapy compared with either placebo or no treatment, or alternative therapies in preventing preterm birth after an episode of threatened preterm labour 6

Benefits and Side Effects

• Magnesium supplements have been shown to have benefits in preventing preterm birth and reducing the risk of side effects such as palpitations or tachycardia 6
• However, magnesium supplements can also cause side effects such as diarrhea 6
• The use of magnesium supplements in pregnancy should be carefully monitored and individualized to minimize the risk of side effects and maximize the benefits 3, 4, 5, 6

Dosage and Administration

• The dosage and administration of magnesium supplements in pregnancy vary depending on the specific condition being treated and the individual patient's needs 3, 4, 5, 6
• Magnesium sulfate is commonly administered intravenously, with a loading dose followed by a maintenance dose 3, 4, 5
• The use of magnesium supplements in pregnancy should be guided by a healthcare provider and carefully monitored to ensure safe and effective use 3, 4, 5, 6