Amniotic fluid index

The amniotic fluid index (AFI) is a semi-quantitative measurement of amniotic volume and it is determined by the vertical height of the deepest pocket in each quadrant of the uterus and summing the four measurement, umbilical and fetal parts are excluded from the area. It is a non invasive technique of estimating amniotic fluid volume and its reproducibility and reliability has been demonstrated.

The amniotic fluid is a liquid produced by the fetus, which surrounds the fetus throughout pregnancy. It acts mainly as protection for the fetus and provides an even temperature, cushions external trauma and allows free movement necessary for normal development of the lungs. In labour the even distribution of fluid makes it possible for the force of uterine contraction to be applied early on the cervix when the presenting part is high. The volume of fluid present is an important indicator of fetal condition if less than 2cm in two perpendicular plane is seen then oligohydramnios may be suspected. The presence of a pool of more than 8 cm suggest a diagnosis of polyhydramnios and may be associated with fetal anomalies or gestational diabetes.