Uterine contractions are when the whole abdomen feels hard or tight, and even painful. However, when the fetus is moving or when the fetus grows and the uterine band is pulled, it also seems to be a contraction of the uterus. The precursors of late miscarriage include paroxysmal uterine contractions. During pregnancy, due to the growth and development of the fetus and the need for subsequent delivery, a series of adaptive physiological changes occur in various systems of the mother’s body, among which the uterus of the reproductive system changes most significantly. The uterus nurtures the fetus, and as the fetus develops and grows and the placenta produces hormones, the uterus becomes significantly larger and softer, its uterine cavity volume increases by 1000 times, and the weight of the uterus increases by 20 times. The main histological changes are the hypertrophy of the uterine myocytes and the filling of the cytoplasm with actin and myoplasmic globulin, which have contractile activity and provide the material conditions for the uterine contraction after labor. Uterine contractions often occur during pregnancy, both physiologically and pathologically. When contractions occur during pregnancy, the frequency and duration of contractions should be noted. Once the contractions become regular and painful, they are beyond the scope of physiological contractions and have entered the pathological state. But before the full term, the uterus has a regular tightness every hour, such as once every 10 or 15 minutes, and if it does not improve after bed rest, then this is an early contraction of the uterus, and if it has not reached 37 weeks, it is likely to cause preterm labor, and it is necessary to take bed rest or come to the hospital immediately for appropriate treatment.