Early gestation amniotic fluid is colorless and clarified liquid, full-term amniotic fluid is slightly turbid, opaque, amniotic fluid is often suspended in small flakes, including fetal fat, fetal shed epithelial cells, cui-ui hair, hair, a small number of leukocytes, albumin, urate and so on, early pregnancy amniotic fluid is mainly from the mother’s serum through the fetal membranes into the amniotic cavity of the dialysis fluid. After the middle of pregnancy fetal urine is an important source of amniotic fluid, late pregnancy fetal lungs are also involved in the generation of amniotic fluid, 50% of the absorption of amniotic fluid is completed by the fetal membranes, amniotic fluid in the amniotic cavity is constantly changing liquid to maintain a relatively constant amount of amniotic fluid. The exchange of amniotic fluid with the fetus is accomplished primarily through the fetal alimentary canal, respiratory tract, urinary tract, and prekeratinized skin.