title: Unconditional reference values for the amniotic fluid index measurement between 26w0d and 41w6d of gestation in low-risk pregnancies.
abstract: OBJECTIVE
  To establish reference values for the amniotic fluid index (AFI) measurement between 26w0d and 41w6d of gestation in a Brazilian population.
  
  
  METHODS
  We performed a cross-sectional study with 1984 low-risk singleton pregnant women between 26w0d and 41w6d of gestation. AFI was measured according to the technique proposed by Phelan et al. Maternal abdomen was divided into four quadrants using the umbilicus and linea nigra as landmarks. Single vertical pocket in each quadrant was measured and the AFI was generated by the sum of these four values without umbilical cord or fetal parts. All ultrasound exams were performed by only two experienced examiners. AFI was expressed as median, interquartile range, mean and ranges in each gestational age (GA) interval. Polynomial regressions were performed to obtain the best fit with adjustment by the determination coefficient (R(2)).
  
  
  RESULTS
  Mean of AFI ranged from 14.0 ± 4.1 cm (range, 9.7-14.0) at 26w0d to 8.3 ± 4.7 cm (range, 1.9-16.5) at 41w6d, respectively. The best polynomial regression fit curve was a first-degree: AFI = 16.29-0.125*GA (R(2) = 0.01). According the scatterplot, AFI values practically did not vary with advancing GA.
  
  
  CONCLUSIONS
  Reference values for the AFI measurement between 26w0d and 41w6d of gestation in a low-risk Brazilian population were established.
authors.affiliation: a Mário Palmério University Hospital, University of Uberaba (UNIUBE) , Uberaba , MG , Brazil .|b Radiologic Clinic of Uberaba (CRU) , Uberaba , MG , Brazil .
authors.forename: Alberto Borges
authors.initials: AB
authors.lastname: Peixoto
authors.affiliation: a Mário Palmério University Hospital, University of Uberaba (UNIUBE) , Uberaba , MG , Brazil .|b Radiologic Clinic of Uberaba (CRU) , Uberaba , MG , Brazil .
authors.forename: Taciana Mara Rodrigues da Cunha
authors.initials: TM
authors.lastname: Caldas
authors.affiliation: c Department of Obstetrics and Gynecology , Ribeirão Preto Medical School, University of São Paulo (DGO-FMRP-USP) , Ribeirão Preto, SP , Brazil .
authors.forename: Wellington P
authors.initials: WP
authors.lastname: Martins
authors.affiliation: d Department of Perinatal Medicine , Royal Women's Hospital and Department of Obstetrics and Gynaecology, University of Melbourne , Melbourne , Victoria , Australia , and.
authors.forename: Fabricio
authors.initials: F
authors.lastname: Da Silva Costa
authors.affiliation: e Department of Obstetrics , Paulista School of Medicine, Federal University of São Paulo (EPM-UNIFESP) , São Paulo, SP , Brazil.
authors.forename: Edward
authors.initials: E
authors.lastname: Araujo Júnior
mesh_terms: D000293:Adolescent; D000328:Adult; D000653:Amniotic Fluid; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D012016:Reference Values; D012189:Retrospective Studies; D055815:Young Adult
keywords: Amniotic fluid volume; low-risk population; pregnant woman; reference values