The maximum amniotic fluid depth is appropriate between 2-8cm. The maximum amniotic fluid depth refers to the maximum vertical depth of the amniotic pool under ultrasound monitoring, and the normal value of the maximum amniotic fluid depth is 2-8cm. If ≤2cm indicates too little amniotic fluid, ≥8cm indicates too much amniotic fluid, whether it is too little amniotic fluid or too much amniotic fluid, it is not a good sign. Low amniotic fluid is mainly due to low amniotic fluid production or increased leakage of amniotic fluid, such as fetal structural abnormalities with urinary system abnormalities being the most common, as well as placental hypoplasia and premature rupture of membranes. Low amniotic fluid can cause pressure outside the uterus to act directly on the fetus, which can easily cause fetal plagiocephaly, hand and foot deformities, etc. One third of excessive amniotic fluid has unknown causes, also because of abnormalities in fetal structure, such as neurological and digestive abnormalities, pregnancy complications, etc. Excessive amniotic fluid is prone to premature rupture of membranes, preterm labor, placental abruption, etc., and also increases the risk of postpartum hemorrhage.