title: Assessing the optimal definition of oligohydramnios associated with adverse neonatal outcomes.
abstract: OBJECTIVE
  The purpose of this study was to compare the use of an amniotic fluid index (AFI) less than 5 cm to the use of an AFI less than the fifth percentile for gestational age in predicting adverse perinatal outcomes.
  
  
  METHODS
  This was a retrospective cohort study from 1998 to 2008. Patients with an AFI less than 5 cm and those with an AFI less than the fifth percentile were compared to patients with a normal AFI. The primary outcome measure was neonatal intensive care unit (NICU) admission.
  
  
  RESULTS
  A total of 17,887 patients had complete information for analysis. There were 145 NICU admissions in patients with an AFI less than 5 cm (relative risk, 2.2) compared to 235 in patients with an AFI less than the fifth percentile for gestational age (relative risk, 2.37). The sensitivity and specificity for NICU admission using an AFI less than 5 cm were 10.9% and 95.2% compared to 17.6% and 92.5% for an AFI less than the fifth percentile for gestational age.
  
  
  CONCLUSIONS
  Oligohydramnios defined as an AFI less than the fifth percentile better predicts fetuses at risk for adverse perinatal outcomes compared to an AFI less than 5 cm.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Washington University, St. Louis, Missouri, USA. shanksa@wudosis.wustl.edu
authors.forename: Anthony
authors.initials: A
authors.lastname: Shanks
authors.forename: Methodius
authors.initials: M
authors.lastname: Tuuli
authors.forename: Caren
authors.initials: C
authors.lastname: Schaecher
authors.forename: Anthony O
authors.initials: AO
authors.lastname: Odibo
authors.forename: Roxane
authors.initials: R
authors.lastname: Rampersad
mesh_terms: D000653:Amniotic Fluid / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007363:Intensive Care Units, Neonatal / Q000706:statistics & numerical data*; D008297:Male; D008923:Missouri / Q000453:epidemiology; D016104:Oligohydramnios / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D010343:Patient Admission / Q000706:statistics & numerical data; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000379:methods* / Q000706:statistics & numerical data*