Maternal magnesium intake and pregnancy outcome.

The magnesium intakes of 513 women towards the end of the first trimester of pregnancy were calculated from a record of food consumption for one week. Magnesium intake was found to be correlated with weight, length, and head circumference at birth as well as length of gestation up to a threshold of around 3200 g birthweight. Of the seven elements found to be significantly associated with these outcomes of pregnancy, magnesium was third in order of significance, after sodium and chloride. A subsample of mothers were given a supplement which provided 100 mg/day of magnesium during the second and third trimester: there was no effect on the outcome of pregnancy, suggesting that any influence of magnesium was confined to the first trimester or before. A maternal magnesium intake of 300 mg/day was compatible with observed optimum birthweight, length and head circumference.