The amniotic fluid index at 38 weeks of pregnancy is 8-18 centimeters, as measured by ultrasound. The amniotic fluid index at the end of pregnancy is the sum of the four quadrant amniotic fluid depths, whereas ultrasound measurements prior to 36 weeks of gestation are mostly maximal amniotic fluid depths, not the amniotic fluid index. The production and absorption of amniotic fluid is in a state of equilibrium, fetal urine is the main source of amniotic fluid, once an imbalance occurs, there will be too much or too little amniotic fluid, clinically greater than 25 centimeters of amniotic fluid is too much, less than 5 centimeters of amniotic fluid is too little. In the late stages of pregnancy, amniotic fluid is often measured as an indicator to analyze the well-being of the fetus through this value. Excessive amniotic fluid is associated with fetal malformations, multiple pregnancies, gestational diabetes and other factors, but there are also some patients with no obvious reason for the increase, the presence of excessive amniotic fluid prompt further examination to avoid the emergence of malformed babies or the combination of anomalous pregnancies. Once the water breaks, placental abruption and umbilical cord prolapse may occur. Hyponatremia is most common in the late stages of pregnancy and is associated with fetal malformations, placental hypoplasia, and amniotic fluid leakage. Detection of oligohydramnios should be treated promptly, and hospitalization is required to correct it if necessary. The persistence of low amniotic fluid in late pregnancy can lead to intrauterine distress, severe asphyxia and death. If the pregnancy is full term at 38 weeks, if the amniotic fluid abnormality cannot be corrected, or if there is an abnormality in the fetal heart rate monitoring, the pregnancy should be promptly induced or terminated surgically.