How does amniotic fluid form?

In early pregnancy, amniotic fluid is mainly formed by maternal serum and fetal membrane dialysis. When pregnant women reach the third trimester, amniotic fluid is mainly from fetal urine, belonging to a dynamic process. The fetus swallows amniotic fluid at about 600 ml per hour, urinating at about 400 ml per hour, in a dynamic equilibrium process. In the third trimester of pregnancy, a small amount of amniotic fluid is formed by osmosis and secretion of placenta and umbilical cord. Amniotic fluid is an important factor for fetal survival. Amniotic fluid holds the uterine wall apart before the embryo is formed, providing space for the fetus to grow and develop. The amount of amniotic fluid increases as the woman's pregnancy progresses to ensure that the fetus develops properly in the mother.