Usually, the uterus opens within 24 hours after regular contractions, but there are individual differences in the length of time, such as 10-20 hours from regular contractions to opening in primiparous women and 6-16 hours from regular contractions to opening in menstruating women. However, for irregular contractions, it is difficult to determine exactly when the uterus will open. Normal vaginal delivery requires regular contractions. The contractions are often irregular and weak at the beginning, and from the first stage of labor, the contractions start from weak to strong and gradually become regular, with an initial interval of about 5-6 minutes, lasting 20-30 seconds. As the labor progresses, the contraction interval gradually shortens, the duration gradually lengthens, and the uterine opening gradually dilates, and when the uterine opening is fully opened the contraction interval is about 1-2 minutes, and the duration reaches more than 1 minute. When a pregnant woman has contractions and pain, especially when the pain is getting shorter and shorter, she should keep a good attitude, ensure sufficient rest, prepare a waiting bag and go to the hospital obstetrics department for delivery in time.