Normal postpartum contractions are rhythmic, symmetrical, polarized and contractile. The rhythmicity is that the normal contractions are weak and strong for 30-40 seconds and then become weaker and weaker until they disappear and enter an interval of 3-4 minutes. Polarity is the strongest contraction at the base of the uterus and the weakest contraction in the lower part of the uterus, which promotes the dilation of the uterine opening and the descent of the fetal head. If these characteristics of uterine contractions become abnormal, such as short duration of rhythmicity and long intervals, it is called weak contraction, which causes slow dilatation of the uterine orifice, resulting in prolonged labor and fatigue and weakness of the pregnant woman. If the polarity of uterine contraction is abnormal, the contraction force of the lower part of the uterus is stronger than the bottom of the uterus, the opening of the uterus does not dilate and the fetal head does not descend. The pregnant woman will have pain in the lower abdomen and refuse to press, and if the time is too long, amniotic fluid and fetal distress will easily occur. Therefore, the characteristics of uterine contractions should be closely observed during labor, and abnormalities should be detected and dealt with in a timely manner to reduce the adverse outcomes for the mother and the perinatal child.