amniotic fluid index

The amniotic fluid index (AFI) is an estimate of the amniotic fluid volume in a pregnant uterus. It is part of the fetal biophysical profile.

Technique

• the uterus is divided into four imaginary quadrants with the linea nigra and a mediolateral line running through the umbilicus acting as the vertical and the horizontal axes respectively
• the deepest pocket devoid of an umbilical cord and fetal parts is measured in the vertical dimension
• measurement of the four pockets is in centimeters
• the sum of all the four quadrant measurements is the AFI
• normal AFI values range from 5 to 25 cm 

Values

The normal range for amniotic fluid volumes varies with gestational age. Typical values include:

• AFI between 5-25 cm is considered normal; median AFI level is ~14 cm from week 20 to week 35, after which the amniotic fluid volume begins to reduce
• AFI <5 cm is considered to be oligohydramnios
  • value changes with age: the 5 percentile for gestational ages is most often taken as the cut-off value, and this is around an AFI of 7 cm for second and third-trimester pregnancies; an AFI of 5 cm is two standard deviations from the mean
• AFI >25 cm is considered to be polyhydramnios

Siehe auch:

• Oligohydramnion
• Polyhydramnion
• amniotic fluid volumes
• fetal biophysical profile

und weiter:

• obstetric curriculum
• amniotic fluid volume
• two diameter pocket method
• maximal vertical pocket method