The functions of amniotic fluid are as follows: 1, to protect the fetus: a certain volume of amniotic fluid can provide a larger range of activities for the fetus, so that the fetus can do appropriate breathing exercises and limb activities in the uterine cavity to prevent joint fixation, limb deformities and fetal limb adhesions, which is conducive to fetal development; 2, to maintain a constant intrauterine temperature: amniotic fluid can maintain a constant temperature in the uterine cavity, so that the metabolic activities in the fetus can be carried out in a normal and stable 3, conducive to fetal fluid balance: the fetus can rely on amniotic fluid to protect its fluid balance. When the fetus has too much water in the body, can be discharged into the amniotic fluid through the fetal urine; dehydration, in addition to restraint in drainage, can also swallow amniotic fluid to compensate; 4, buffer external pressure: amniotic fluid has the role of balancing external pressure, can significantly reduce the impact of external violence, to protect the fetus. The right amount of amniotic fluid can also avoid the uterine wall and fetal direct pressure on the umbilical cord, resulting in fetal hypoxia; 5, the role of labor: when the contraction of the uterus, intrauterine pressure increases, amniotic fluid can conduct pressure in the cervical part of the uterus, the formation of the front amniotic fluid sac before the fetal head pre-disclosure, expansion of the internal and external cervical opening and vagina, and can reduce the direct pressure on the maternal tissues due to limbs for too long, and the damage caused by the cervix and vagina.