The effectiveness of allylestrenol tablets in preserving fetus varies from person to person. Generally speaking, it is more effective for preterm miscarriage, habitual miscarriage, and preterm labor due to simple luteal deficiency, and has less impact on the fetus and a lower probability of side effects. However, it may not be effective for miscarriage due to some specific causes such as trauma, cardiovascular disease, and infection. The main ingredient of Allylestrenol tablets is Allylestrenol, which works by increasing the endocrine activity of the placental trophoblast, normalizing the placental function, and increasing the concentration and activity of oxytocin enzyme. It reduces the level of oxytocin in pregnant women, antagonizes the stimulating effect of prostaglandins on the uterus, inhibits contractions, maintains pregnancy, and has a better effect on miscarriage caused by luteal deficiency. In case of pre-eclampsia, the medication is usually administered for 5-7 days, and in case of habitual abortion, it needs to be used until one month after the risk period. Patients may experience nausea, headache, edema and other symptoms after using the drug, and it can reduce glucose tolerance, so pregnant women with diabetes should monitor their blood sugar level regularly when taking this drug. In addition, pregnant women with severe liver dysfunction, herpes in pregnancy or hypertensive disorders during pregnancy are prohibited from using this drug in principle.