The amniotic fluid before full term is a colorless and clear liquid, but at full term it is slightly cloudy, opaque and mixed with white flocculent material because of fetal fat, cells shed from fetal skin and hair, etc. The volume of amniotic fluid is about 800-1000ml, of which more than 90% is amniotic fluid, and the other contains minerals, uric acid, urea, etc. This is the normal form of amniotic fluid. The main role of amniotic fluid is the following five points: 1) to protect the fetus, to provide more space for the fetus to move, so that the fetus can do some appropriate breathing exercises and other body movements in the uterus. 2) to maintain a constant temperature in the uterus, so that the fetus’s internal metabolic activities can be carried out under normal and stable conditions. 3) to facilitate the balance of fetal body fluids, for example, the fetus can urinate if there is too much water in the body. The fetus can also be protected by the pressure of the outside world, which can reduce the impact of external violence. 5, when in labor, the contraction pressure is transmitted to the cervix, which can dilate the cervix.