Amniotic fluid index
Citation, DOI, disclosures and article data
At the time the article was created Yuranga Weerakkody had no recorded disclosures.
View Yuranga Weerakkody's current disclosuresAt the time the article was last revised Calum Worsley had no financial relationships to ineligible companies to disclose.
View Calum Worsley's current disclosures- Amniotic fluid index (AFI)
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
Values
The normal range for amniotic fluid volumes varies with gestation 4. Median AFI level is ~14 cm from week 20 to week 35, after which the amniotic fluid volume begins to reduce.
Typical values include:
-
AFI <5 cm is considered to be oligohydramnios
value changes with age: the 5th 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
the cutoff for diagnosis of polyhydramnios is dependent on local guidelines with either 24 cm 5,6 or 25 cm 7 taken to be the upper limit of normal.
References
- 1. Magann E, Sanderson M, Martin J, Chauhan S. The Amniotic Fluid Index, Single Deepest Pocket, and Two-Diameter Pocket in Normal Human Pregnancy. Am J Obstet Gynecol. 2000;182(6):1581-8. doi:10.1067/mob.2000.107325 - Pubmed
- 2. Hallak M, Kirshon B, Smith E, Cotton D. Amniotic Fluid Index. Gestational Age-Specific Values for Normal Human Pregnancy. J Reprod Med. 1993;38(11):853-6. - Pubmed
- 3. Porter T, Dildy G, Blanchard J, Kochenour N, Clark S. Normal Values for Amniotic Fluid Index During Uncomplicated Twin Pregnancy. Obstet Gynecol. 1996;87(5 Pt 1):699-702. doi:10.1016/0029-7844(96)00006-3 - Pubmed
- 4. Regina Machado M, Guilherme Cecatti J, Krupa F, Faundes A. Curve of Amniotic Fluid Index Measurements in Low‐risk Pregnancy. Acta Obstet Gynecol Scand. 2007;86(1):37-41. doi:10.1080/00016340600994976 - Pubmed
- 5. Dashe J, Pressman E, Hibbard J. SMFM Consult Series #46: Evaluation and Management of Polyhydramnios. Am J Obstet Gynecol. 2018;219(4):B2-8. doi:10.1016/j.ajog.2018.07.016 - Pubmed
- 6. https://www.tewhatuora.govt.nz/assets/Publications/Maternity/new-zealand-obstetric-ultrasound-guidelines-2019-dec19.pdf
- 7. https://www.bmus.org/static/uploads/resources/SIG3_document_FINAL__v_16__27_Jan_2022-_With_cover_QcOJnLN.pdf
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