The amniotic fluid index (AFI) is a semi-quantitative assessment of amniotic fluid volume. The uterus is divided into four quadrants and the deepest vertical pocket of fluid in each quadrant (avoiding the umbilical cord) is measured in centimeters. The four measurements are summed to produce the AFI. A normal AFI is approximately 8–24 cm. Values below 5 cm indicate oligohydramnios; values above 24 cm indicate polyhydramnios. AFI is a component of the biophysical profile and antepartum surveillance.