Amniotic fluid is not only fetal urine, but comes from different sources at different stages of pregnancy. Amniotic fluid is the internal environment for fetal growth and development, and is mainly derived from maternal serum via fetal membranes in early pregnancy, fetal urine in mid-pregnancy, and fetal alveolar fluid in addition to fetal urine in late pregnancy. Fetal swallowing is the main mode of absorption of amniotic fluid and is exchanged between the mother and fetus to maintain dynamic balance. The amount of amniotic fluid increases gradually with each week of pregnancy, reaching 1000 ml at 38 weeks of gestation and 800 ml at 40 weeks of gestation. amniotic fluid in early pregnancy is colorless and transparent, and after full term, it is slightly turbid and may contain fetal fat and fetal hair. Amniotic fluid mainly plays the role of protecting the fetus and the mother’s body, when there is premature rupture of membranes should go to the hospital in time.