Amniotic fluid index

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Amniotic fluid index (AFI) is an estimate of the amount of amniotic fluid[1] and is an index for the fetal well-being. It is a part of the biophysical profile.[1]

AFI is the score (expressed in cm) given to the amount of amniotic fluid seen on ultrasonography (aka ultrasound) of a pregnant uterus. To determine the AFI, doctors may use a four-quadrant technique,[2] when the deepest, unobstructed, vertical length of each pocket of fluid is measured in each quadrant and then added up to the others,[3] or the so-called "Single Deepest Pocket" technique.[4]

  • An AFI between 8-18 is considered normal.[5] Median AFI level is approximately 14 from week 20 to week 35,[6] when the amniotic fluid begins to reduce in preparation for birth.
  • An AFI < 5-6 is considered as Oligohydramnios[3] The exact number can vary by gestational age. The fifth percentile for gestational age is sometimes used as a cutoff value.[7]


  1. ^ a b Tom C Winter; Sanders, Roger C. (2006). Clinical Sonography: A Practical Guide. Hagerstown, MD: Lippincott Williams & Wilkins. pp. p502. ISBN 0-7817-4869-0. 
  2. ^
  3. ^ a b c Carr, Phyllis L.; Ricciotti, Hope; Freund, Karen M.; Scott Kahan (2003). In a Page Ob/Gyn & Women's Health (In a Page). Cambridge, MA: Blackwell Publishers. pp. p105. ISBN 1-4051-0380-9. 
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  7. ^ Griffin M, Attilakos G, Greenwood R, Denbow M (2009). "Amniotic fluid index in low-risk, post-dates pregnancies". Fetal. Diagn. Ther. 26 (4): 212–5. doi:10.1159/000265554. PMID 20029220. 
  8. ^ Sylvia Dobo; Mitchell King; Lipsky, Martin S.; Jeff Susman (2003). Family Medicine Certification Review. Cambridge, MA: Blackwell Publishers. pp. p133. ISBN 1-4051-0329-9.