The role of magnesium sulfate on pregnant women, there are mainly the following aspects, different roles, for the situation is different, as follows: 1, fetal protection, magnesium sulfate has the role of inhibiting uterine contractions, through the inhibition of uterine contractions, can achieve the purpose of fetal protection, prolonging the pregnancy week; 2, improve the blood supply to the placenta of the fetus, to protect the baby’s brain nerves. General premature pregnant women will routinely use magnesium sulfate, through magnesium sulfate to expand the placenta and fetal brain blood vessels, can promote better development of the baby’s brain; 3, antispasmodic and hypotensive, hypertensive patients in pregnancy in the antispasmodic and hypotensive preferred magnesium sulfate, the use of magnesium sulfate can reduce the probability of eclampsia, can be more effective in making patients with hypertension more stable blood pressure. Therefore, the clinical use of this drug in obstetrics is still very widespread.