Amniotic fluid volume

Dr Owen Kang and Radswiki et al.

Amniotic fluid volume (AFV) is a function both of the amount of water transferred to the gestation across the placental membrane, and the flux of water across the amnion.

The AFV undergoes characteristic changes with gestation. It progressively rises.

  • 10 weeks gestation it is about 10 to 20 mL
  • at 16 weeks gestation  ~250 mL
  • at 33 weeks gestation ~800 mL  
  • at 38-39 weeks reaches a plateau of ~1000 mL  
  • finally decreases at 40 weeks to ~800 mL 

At 8 weeks the volume increases by ~10 mL/week, at 13 weeks the AFV increases by 25 mL/week and reaches a maximum rate of 60 mL/week at 21 weeks gestation. The weekly volume increment then decreases and reaches zero at about 33 weeks of gestation at which point the mean AFV reaches its peak. After term the amniotic fluid volume declines at a rate of ~8% per week. During the first half of pregnancy, amniotic fluid volume is closely correlated with fetal weight. The ratio of amniotic fluid to fetal volume increases until about 30 weeks gestation and then appears to decline.

Ultrasound is the modality of choice of assessing amniotic fluid volumes. The AFV can be assessed by ultrasound by using 3 main indirect parameters:

Ultrasound - obstetric
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Article information

rID: 14554
System: Obstetrics
Section: Approach
Tag: cases
Synonyms or Alternate Spellings:
  • Amniotic fluid volume
  • Amniotic fluid volumes
  • Volume of amniotic fluid
  • Amniotic fluid volume (AFV)
  • Amniotic fluid volumes (AFV)
  • Liquor volume
  • Liquor volumes

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