A depth of amniotic fluid of 7.5 cm is normal and is a normal physiologic manifestation of pregnancy. The normal value of the vertical depth of the maximum dark zone of amniotic fluid is 2-8 cm. amniotic fluid mainly comes from maternal blood in early pregnancy; fetal urine is the source of amniotic fluid after the middle of pregnancy; fetal lungs are involved in the generation of amniotic fluid in late pregnancy; amniotic umbilical cord, huatong gel, and fetal skin can exude fluids, but the amount is relatively small. Fetal swallowing is the main mode of amniotic fluid absorption, and the fetus develops swallowing motions beginning at 18 weeks of gestation. Amniotic fluid is constantly exchanged for fluid in the amniotic cavity to keep the amount of amniotic fluid relatively constant. If there is a change in the vertical depth of the darkest area of the amniotic fluid maximum, you should go to the hospital and follow the doctor’s instructions.