Magnesium sulfate intravenous injection, easy to cause hot flashes sweating dry mouth and other symptoms, if the injection speed is too fast, but also cause gastrointestinal reactions, such as nausea, vomiting, panic, dizziness, etc., renal insufficiency, with a large dose of the drug, but also easy to appear respiratory depression, respiratory arrest, arrhythmia problems. So the use of magnesium sulfate must be careful, usually gynecologists, more accustomed to use magnesium sulfate for fetal preservation treatment, mainly to relieve smooth muscle spasm, so that the uterus completely relaxed, generally choose the way of intravenous infusion, usually can be used for 4 to 5 days continuously.