title: Is bacterial vaginosis a stronger risk factor for preterm birth when it is diagnosed earlier in gestation?
abstract: OBJECTIVE
  It is stated commonly that the earlier in pregnancy bacterial vaginosis is diagnosed, the greater is the increase in risk of preterm birth compared with women without bacterial vaginosis. However, this contention is based on small numbers of women.
  
  
  METHODS
  In this analysis of 12,937 women who were screened for bacterial vaginosis as part of a previously conducted clinical trial, the odds ratio of preterm birth (<7 weeks of gestation) for asymptomatic bacterial vaginosis-positive versus bacterial vaginosis-negative women was evaluated among women who were screened from 8 to 22 weeks of gestation.
  
  
  RESULTS
  The odds ratio of preterm birth among bacterial vaginosis-positive versus bacterial vaginosis-negative women ranged from 1.1 to 1.6 and did not vary significantly according to the gestational age at which bacterial vaginosis was screened. The odds ratio for preterm birth did not vary significantly by gestational age at diagnosis when bacterial vaginosis was subdivided into Gram stain score 7 to 8 or 9 to 10.
  
  
  CONCLUSIONS
  Although bacterial vaginosis was associated with an increased risk of preterm birth, the gestational age at which bacterial vaginosis was screened for and diagnosed did not influence the increase.
authors.affiliation: National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA. mk90h@nih.gov
authors.forename: Mark A
authors.initials: MA
authors.lastname: Klebanoff
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Hillier
authors.forename: Robert P
authors.initials: RP
authors.lastname: Nugent
authors.forename: Cora A
authors.initials: CA
authors.lastname: MacPherson
authors.forename: John C
authors.initials: JC
authors.lastname: Hauth
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Carey
authors.forename: Margaret
authors.initials: M
authors.lastname: Harper
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Wapner
authors.forename: Wayne
authors.initials: W
authors.lastname: Trout
authors.forename: Atef
authors.initials: A
authors.lastname: Moawad
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Leveno
authors.forename: Menachem
authors.initials: M
authors.lastname: Miodovnik
authors.forename: Baha M
authors.initials: BM
authors.lastname: Sibai
authors.forename: J Peter
authors.initials: JP
authors.lastname: Vandorsten
authors.forename: Mitchell P
authors.initials: MP
authors.lastname: Dombrowski
authors.forename: Mary J
authors.initials: MJ
authors.lastname: O'Sullivan
authors.forename: Michael
authors.initials: M
authors.lastname: Varner
authors.forename: Oded
authors.initials: O
authors.lastname: Langer
mesh_terms: D005260:Female; D005865:Gestational Age; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D016017:Odds Ratio; D011247:Pregnancy; D047928:Premature Birth / Q000209:etiology*; D012307:Risk Factors; D016585:Vaginosis, Bacterial / Q000150:complications* / Q000175:diagnosis