In a full-term pregnancy, the amniotic fluid volume is 800-1000 ml, or 2 pounds. If the amniotic fluid volume exceeds 2000 ml at any time of pregnancy, it is called excessive amniotic fluid, and the general incidence is 0.5%-1%. If the amniotic fluid volume is less than 300 ml in late pregnancy, the amniotic fluid volume is called hypohydramnios, and the incidence is generally 0.4%-4%. Clinically, the amount of amniotic fluid is determined by ultrasound, mainly based on two indicators: first, the amniotic fluid index; second, the depth of amniotic fluid. The normal range of amniotic fluid index is 8-25cm, and the depth of amniotic fluid is between 2-8cm. If it is higher than the normal range or lower than the normal range, it is an abnormal condition.