There is no such thing as the best birth control pill, but rather which one is the most suitable. During pregnancy, some pregnant mothers may experience signs of preterm miscarriage or even miscarriage in the early and middle stages of pregnancy. In the late stage of pregnancy, some pregnant mothers may show signs of preterm labor and even develop preterm labor. Therefore, depending on the situation, the appropriate treatment is given, and these causes of preterm labor or miscarriage require the application of different medications. In early pregnancy, additional progesterone supplementation is required because of luteal insufficiency, and the progesterone supplementation is considered a fetal preservation drug. In addition, some pregnant mothers in the early stages of pregnancy may need to use low molecular heparin or low dose aspirin for miscarriage due to immune factors because of positive antiphospholipid antibodies. Premature miscarriage and preterm labor in the middle and late stages of pregnancy are mostly related to contractions, so the medication needed in this case is often one that inhibits the contractions of the uterus. Therefore, when choosing the medication, it is important to let the doctor give the fetus preservation medication according to the specific condition, and the medication used according to the condition is the best fetus preservation medication.