There is a general consensus in the medical community regarding the use of contraction suppressants: they are intended primarily for short-term suppression of acute contractions to buy time to promote fetal lung maturation and safe intrauterine transfer of the fetus to a hospital equipped to resuscitate preterm infants. In other words, contraction suppressants cannot meet the expectations of extending the gestational weeks to weeks or even months. It is generally accepted that contraction suppressants are only effective in suppressing contractions for 48 hours, and we recommend their use only if we evaluate that suppressing contractions for 48 hours is beneficial to the mother and child. 1. Mechanism of action and side effects of various contraction inhibitors Prostaglandin inhibitors (indomethacin, also known as anti-inflammatory pain): inhibit prostaglandin synthesis by inhibiting cyclooxygenase, thereby inhibiting contractions. Compared with placebo, indomethacin significantly reduces preterm labor at 48 h versus 7 d (95% CI 0.34-1.02) and also at 37 weeks of gestation (95% CI 0.31-0.94). It is mainly indicated before 32 weeks. Side effects: maternal, gastrointestinal irritation, dizziness and discomfort, hepatic and renal aspects, rash, allergic reactions, hemorrhagic disorders; pediatric, use after 32 weeks of gestation may cause premature closure of the fetal ductus arteriosus and low amniotic fluid. Calcium channel blockers (nifedipine, also known as cardiac painkillers): interfere with intracellular Ca2+ concentration by selectively reducing Ca2+ inward flow, thereby inhibiting uterine contractions. It has been reported in the literature to reduce 24% of preterm births within 7 d and 17% of preterm births before 34 weeks of gestation, and to reduce 37% of neonatal respiratory distress syndrome, 79% of necrotizing microcephaly, and 41% of periventricular hemorrhage. The meta-analysis suggests that it may be superior to other contraction inhibitors. Side effects: Blood pressure and heart rate changes mainly in the mother. No significant side effects were found in the fetus. β2 adrenergic agonist (ritodrine, also known as Ampro): Inhibits uterine smooth muscle contraction by activating intracellular adenylate cyclase. The literature suggests that ritodrine reduces the preterm birth rate by 37% within 48 h and 33% within 7 d, but does not necessarily reduce the incidence of neonatal respiratory distress syndrome and perinatal mortality. Side effects: mother, panic attacks, shortness of breath, headache, hyperglycemia, hypokalemia, pulmonary edema, myocardial ischemia, water and sodium retention …… children, mainly rapid heart rate. Contractile hormone receptor antagonist (atosiban, also known as epoetin): selective contractile hormone receptor antagonist that inhibits uterine contraction by competitively binding to uterine smooth muscle contractile hormone receptors. Side effects: mild, no clear contraindications . Magnesium sulfate high concentration of magnesium ions directly on the uterine smooth muscle cells, antagonize calcium ions and inhibit uterine contraction. 2.Should we use contraction inhibitors? The first thing to tell you is that we often overuse contraction inhibitors in the clinic. “A little redness, a little contraction, a little discomfort”, the doctor should consider whether it is “preterm labor”. This is our bad habit, partly due to the current medical environment, doctors do not dare not to prescribe “birth control drugs”, patients feel uneasy not to prescribe drugs, eat more at ease. Especially this group of “unreasonable” cervical patients, often give Dr. Liu medical advice: Dr. Liu, give me * box of An Bao, * box of Angioten… Many times it is educational brainwashing, but there are times when you have to compromise! Because home is too far, because the doctor is not convenient, because the old home does not have such drugs … but repeatedly instructed the method of medication, instructed not to take drugs as “sugar beans” to eat! Some drugs are calculated for 48 hours, and not even one more piece is prescribed to save you from taking more. I was told to be moderately active and not to be bedridden every day, but I often found: I was fooled again! So, take a closer look at the side effects of these drugs and the implications of their use. I’m afraid I won’t list in detail how the drugs are used because I’m worried that you won’t use them under the guidance of your doctor! Looking at the international guidelines for the management of contraction inhibitors, they are not recommended in many cases, such as before the fetus has viability; after 34 weeks; or when contractions do not cause cervical changes, or even before the uterine opening is 2 cm dilated, nor is it recommended for pregnant women to monitor contractions at home by themselves. The reason is that the current evidence suggests that contraction suppressants can only suppress contractions for about 48 hours and cannot prolong them much longer to eliminate the effect of this potential stimulus on the labor process. 3. How to choose a contraction suppressant? Currently, there is no clear recommendation on the selection of contraction inhibitors in the order of priority in our domestic guidelines. Therefore, we rely more on doctors’ experience and medication habits in clinical practice. The recommendations of international guidelines are relatively clear. In the United States, indomethacin is recommended as the first-line drug for weeks 24-32, based on the results of randomized controlled trials and in combination with its side effects. For 32-34 weeks, nifedipine is recommended, based on consideration of the side effects of indomethacin on the fetus after 32 weeks and the Meta-analysis that it is in many ways due to other contraction inhibitors. In view of the relatively high side effects, Epro is no longer used as a first-line drug in the United States. The biggest “side effect” of EPRO is that it is expensive and is widely used in Europe, but not as widely used in the United States as in Europe. A 2009 systematic review evaluated randomized controlled trials of magnesium sulfate for contraction inhibition in 334 fetuses/newborns and compared magnesium sulfate for contraction inhibition with placebo/no intervention and found no value of magnesium sulfate for contraction inhibition. value. It was neither effective in reducing preterm birth rates at 48 hours, 7 days, and 37 weeks, nor in reducing neonatal respiratory distress syndrome, ventricular hemorrhage, or neonatal mortality. In addition, the FDA warns that continuous use of magnesium sulfate for 5-7 days can cause fetal bone decalcification. Therefore, the safety classification of magnesium sulfate for use during pregnancy was changed from category A to category D. However, the protective effect of magnesium sulfate on the fetal central nervous system was found, and now domestic and international guidelines have reached a consensus in this regard. Only Chinese textbooks have not yet completely discarded the role of magnesium sulfate in the treatment of preterm birth.