title: Borderline amniotic fluid index and its relation to fetal intolerance of labor: a 2-center retrospective cohort study.
abstract: OBJECTIVE
  To determine whether a borderline amniotic fluid index (AFI) in the third trimester is associated with an increased rate of cesarean delivery for fetal intolerance of labor, meconium-stained amniotic fluid, and intrauterine growth restriction, among other adverse perinatal outcomes.
  
  
  METHODS
  Patients with a diagnosis of a borderline AFI between January 2008 and August 2012 were identified. Antepartum, delivery, and neonatal data were collected and compared to a cohort with a normal AFI.
  
  
  RESULTS
  We enrolled 739 patients, including 177 with a borderline AFI (>5 and <10 cm) and 562 with a normal AFI (≥ 10-24 cm); 360 patients delivered at University of Arizona Medical Center, and 379 delivered at St Joseph's Hospital. Combined and individual analyses of each center revealed no significant difference in fetal intolerance of labor (P = .19) or cesarean delivery for fetal intolerance (P = .074) between cohorts. In both settings, patients with a borderline AFI were more likely than those with a normal AFI to undergo antepartum testing (P < .001). A statistically significant increase in intrauterine growth restriction in the borderline AFI group was noted, with a calculated risk ratio of 13.76 (P < .001). There was no difference between groups for meconium-stained amniotic fluid (P = .23), neonatal intensive care unit admission (P = .054), preterm delivery (P = .31), or operative vaginal delivery (P = .45).
  
  
  CONCLUSIONS
  The findings of this study suggest that there is no difference in the rate of fetal intolerance of labor in pregnancies with a borderline AFI and those with a normal AFI. Pregnancies complicated by a borderline AFI are more likely to undergo antepartum testing, yet the benefit is unclear. Significantly more patients with a borderline AFI had underlying growth restriction, which may provide a useful tool for risk stratification in the management of a borderline AFI.
authors.affiliation: Department of Obstetrics and Gynecology, University of Arizona, 1501 N. Campbell Ave, Tucson, AZ 85724 USA. lwood@obgyn.arizona.edu.
authors.forename: S Lindsay
authors.initials: SL
authors.lastname: Wood
authors.forename: J Michael
authors.initials: JM
authors.lastname: Newton
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Karen
authors.initials: K
authors.lastname: Lesser
mesh_terms: D000653:Amniotic Fluid / Q000166:cytology* / Q000000981:diagnostic imaging; D001130:Arizona / Q000453:epidemiology; D002585:Cesarean Section / Q000706:statistics & numerical data*; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D005317:Fetal Growth Retardation / Q000175:diagnosis* / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D016104:Oligohydramnios / Q000175:diagnosis* / Q000453:epidemiology*; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000706:statistics & numerical data*
keywords: borderline amniotic fluid index; fetal intolerance of labor; low amniotic fluid index; obstetric ultrasound