Except in severe eclampsia with seizures, the rate of IV infusion should not exceed 150 mg/minute (1.5 mL of a 10% concentration or its equivalent). Continuous maternal magnesium sulfate dosing in pregnancy after 5 to 7 days might result in fetal defects. The American College of Obstetricians and Gynecologists recommends a maximum dose of 4 g per day (or 100 mmol per day), with no more than two doses per day. The safety of IV magnesium for neuroprotection in preterm labor has been established. However new data from animal studies as well as clinical trials in adults and children suggest that high-dose intravenous magnesium may be neurotoxic. Therefore current guidelines recommend only low-dose intravenous magnesium for neuroprotection in preterm labor. For anticonvulsant activity, we recommend a dose of 0.5 to 1 gram per kilogram of body weight per day administered over a period of at least 24 hours. Intravenous magnesium is generally well tolerated by pregnant women. The most common side effects include diarrhea, nausea, and vomiting. Large doses can cause muscle cramping, confusion, and respiratory problems. Rare cases of hypermagnesemia have been reported in patients receiving high doses of intravenous magnesium. High-dose intravenous magnesium is not recommended for neuroprotection in preterm labor.