The normal range of amniotic fluid at 37 weeks of pregnancy is 300ml-2000ml. the normal range of liquid dark area (AFV) on B-mode ultrasound is 3cm-8cm and the normal range of amniotic fluid index (AFI) is 8cm-25cm. clinically, according to the amount of amniotic fluid, the abnormalities are divided into the following two types: 1. excessive amniotic fluid. The diagnosis of excessive amniotic fluid can be made by B-mode ultrasound examination as AFV greater than or equal to 8cm or AFI greater than or equal to 25cm, which is mainly related to fetal malformation, multiple pregnancy, gestational diabetes, etc. 2, low amniotic fluid can be diagnosed by B-mode ultrasound examination as AFV less than or equal to 2cm or AFI less than or equal to 5cm, which is mainly related to fetal malformation and placental hypoplasia. The treatment is mainly based on the presence or absence of fetal malformation and the size of the gestational week to choose the appropriate treatment plan.