Maternal and fetal serum concentrations of magnesium after administration of a 6-g bolus dose of magnesium sulfate (MgSO 4 ) to women with imminent preterm delivery.

A bolus dose of 6 g magnesium sulfate was well tolerated and without any serious side effects in either mother or infant. Most of our women reached the targeted concentration range of serum magnesium levels after infusion was completed. Their infants had magnesium levels within acceptable levels, regardless of gestational week or mother's body mass index.