4.38\ Amniotic Fluid Index (AFI)

Fig. 13.52  Section of amniotic fluid index measurement. The maternal abdominal wall is divided into four quadrants; the deepest volume pool of each quadrant is measured and added up as AFI. Q1 amniotic fluid depth of the

first quadrant, Q2 amniotic fluid depth of the second quadrant, Q3 amniotic fluid depth of the third quadrant, Q4 amniotic fluid depth of the fourth quadrant

4.38.1\ Scanning Method

The maternal abdomen can be divided into four quadrants with the maternal umbilicus as the central point, then the largest and the deepest section of amniotic volume pool is found out in every quadrant, and its deepest volume pool is measured.

4.38.2\ Section Structures

Amniotic volume pool is shown as an irregular anechoic region.

4.38.3\ Measuring Method

AFI is acquired by adding up the deepest volume pools of the four quadrants.

4.38.4\ Clinical Significance

Changes of AFI are often related to fetal anomalies or malformations of digestive system and urinary system.

4.38.5\ Normal Reference Values

It is normal when AFI is between 80 and 200 mm. Oligohydramnios is diagnosed when AFI is smaller than 50 mm, and borderline oligohydramnios is considered when AFI is between 50 and 80 mm. Polyhydramnios is diagnosed when AFI is larger than 250 mm, and borderline polyhydramnios is considered when AFI is between 200 and 250 mm.