Magnesium sulfate fertility preservation treatment is basically applied for 3-5 days in general, and the maximum use time is not more than 7 days. The high concentration of magnesium ions in magnesium sulfate can directly act on the myocytes of the uterus, thus antagonizing calcium ions, reducing the contraction of myocytes, relieving smooth muscle spasms, effectively inhibiting uterine contractions, and achieving the effect of fetal preservation. The use of magnesium sulfate should pay attention to avoid overdose, magnesium sulfate overdose will make the respiratory and cardiac muscle contraction function is inhibited, life-threatening, poisoning phenomenon first for the disappearance of the knee reflex, with the increase of blood magnesium concentration, there can be a generalized hypotonia and respiratory inhibition, the heartbeat of the serious cases can suddenly stop. Therefore, check the knee reflex regularly before and during the medication, the knee reflex must exist, the respiration is not less than 16 times per minute, the urine volume is not less than 600 ml per 24h, and not less than 25 ml per hour, and the urine is less suggesting that the excretory function is inhibited. In addition, magnesium ions are easy to accumulate and toxicity, treatment needs to be prepared calcium as an antidote, when magnesium toxicity, immediately intravenous injection of 10% calcium gluconate 10 ml. Calcium ions can compete with magnesium ions for the same receptor on the nerve cells, preventing magnesium ions continue to combine, thus preventing further deepening of the toxic reaction. Special attention, pregnant women should follow the doctor’s instructions to cooperate with the treatment, and monitor the blood magnesium level on time. Remember not to use the drug arbitrarily on your own, improper use may cause paralytic intestinal obstruction, hypocalcemia, respiratory depression, cardiac arrest, neonatal hypermagnesemia and other adverse reactions, if discomfort occurs in the treatment to communicate with the doctor in time to avoid delaying the condition.