title: Scientific evidence underlying the American College of Obstetricians and Gynecologists' practice bulletins.
abstract: OBJECTIVE
  Clinical guidelines are an important source of guidance for clinicians. Few studies have examined the quality of scientific data underlying evidence-based guidelines. We examined the quality of evidence that underlies the recommendations made by the American College of Obstetricians and Gynecologists (the College).
  
  
  METHODS
  The current practice bulletins of the College were examined. Each bulletin makes multiple recommendations. Each recommendation is categorized based on the quality and quantity of evidence that underlies the recommendation into one of three levels of evidence: A (good and consistent evidence), B (limited or inconsistent evidence), or C (consensus and opinion). We analyzed the distribution of levels of evidence for obstetrics and gynecology recommendations.
  
  
  RESULTS
  A total of 84 practice bulletins that offered 717 individual recommendations were identified. Forty-eight (57.1%) of the guidelines were obstetric and 36 (42.9%) were gynecologic. When all recommendations were considered, 215 (30.0%) provided level A evidence, 270 (37.7%) level B, and 232 (32.3%) level C. Among obstetric recommendations, 93 (25.5%) were level A, 145 (39.7%) level B, and 117 (34.8%) level C. For the gynecologic recommendations, 122 (34.7%) were level A, 125 (35.5%) level B, and 105 (29.8%) level C. The gynecology recommendations were more likely to be of level A evidence than the obstetrics recommendations (P=.049).
  
  
  CONCLUSIONS
  One third of the recommendations put forth by the College in its practice bulletins are based on good and consistent scientific evidence.
authors.affiliation: From the Divisions of Gynecologic Oncology and Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Columbia University College of Physicians and Surgeons, and the Herbert Irving Comprehensive Cancer Center, New York, New York.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Wright
authors.forename: Neha
authors.initials: N
authors.lastname: Pawar
authors.forename: Julie S R
authors.initials: JSR
authors.lastname: Gonzalez
authors.forename: Sharyn N
authors.initials: SN
authors.lastname: Lewin
authors.forename: William M
authors.initials: WM
authors.lastname: Burke
authors.forename: Lynn L
authors.initials: LL
authors.lastname: Simpson
authors.forename: Abigail S
authors.initials: AS
authors.lastname: Charles
authors.forename: Mary E
authors.initials: ME
authors.lastname: D'Alton
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Herzog
mesh_terms: D019317:Evidence-Based Medicine / Q000145:classification / Q000592:standards; D006176:Gynecology / Q000592:standards*; D006801:Humans; D009774:Obstetrics / Q000592:standards*; D017410:Practice Guidelines as Topic / Q000592:standards*; D012955:Societies, Medical; D014481:United States