At 39 weeks of pregnancy, the normal range of amniotic fluid index should be 8-25 centimeters. The so-called amniotic fluid index refers to dividing the uterus into four quadrants and measuring the vertical diameter of the largest pool of amniotic fluid in each quadrant; the sum of the four is the amniotic fluid index. The normal range of amniotic fluid index is between 8-25 centimeters. Now at 39 weeks of pregnancy, if the amniotic fluid index is below 5 centimeters, then this is considered to be too little amniotic fluid. If the amniotic fluid index is above 25 centimeters, then this condition is considered as excessive amniotic fluid. At 39 weeks of pregnancy, the fetus has matured. If the ultrasound examination reveals that the amount of amniotic fluid is too much or too little, it is necessary to closely observe the number of fetal movements and pay attention to the fetal heart monitoring. If you find that the number of fetal movements increases or decreases significantly, you need to go to the hospital for examination.