title: Hormonal contraception is associated with a reduced risk of bacterial vaginosis: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To examine the association between hormonal contraception (HC) and bacterial vaginosis (BV) by systematic review and meta-analysis.
  
  
  METHODS
  Medline, Web of Science and Embase databases were searched to 24/1/13 and duplicate references removed. Inclusion criteria 1) >20 BV cases; 2) accepted BV diagnostic method; 3) measure of HC-use either as combined oestrogen-progesterone HC (combined), progesterone-only contraception (POC) or unspecified HC (u-HC); 4) ≥ 10% of women using HC; 5) analysis of the association between BV and HC-use presented; 6) appropriate control group. Data extracted included: type of HC, BV diagnostic method and outcome (prevalent, incident, recurrent), and geographical and clinic-setting. Meta-analyses were conducted to calculate pooled effect sizes (ES), stratified by HC-type and BV outcome. This systematic review is registered with PROSPERO (CRD42013003699).
  
  
  RESULTS
  Of 1713 unique references identified, 502 full-text articles were assessed for eligibility and 55 studies met inclusion criteria. Hormonal contraceptive use was associated with a significant reduction in the odds of prevalent BV (pooled effect size by random-effects [reES] = 0.68, 95%CI0.63-0.73), and in the relative risk (RR) of incident (reES = 0.82, 95%CI:0.72-0.92), and recurrent (reES = 0.69, 95%CI:0.59-0.91) BV. When stratified by HC-type, combined-HC and POC were both associated with decreased prevalence of BV and risk of incident BV. In the pooled analysis of the effect of HC-use on the composite outcome of prevalent/incident/recurrent BV, HC-use was associated with a reduced risk of any BV (reES = 0.78, 95%CI:0.74-0.82).
  
  
  CONCLUSIONS
  HC-use was associated with a significantly reduced risk of BV. This negative association was robust and present regardless of HC-type and evident across all three BV outcome measures. When stratified by HC-type, combined-HC and POC were both individually associated with a reduction in the prevalence and incidence of BV. This meta-analysis provides compelling evidence that HC-use influences a woman's risk of BV, with important implications for clinicians and researchers in the field.
authors.affiliation: Sexual Health Unit, Melbourne School of Population and Global Health, University of Melbourne, Parkville, Australia ; Melbourne Sexual Health Centre, Alfred Hospital, Carlton, Australia ; Murdoch Children's Research Institute, Parkville, Australia.
authors.forename: Lenka A
authors.initials: LA
authors.lastname: Vodstrcil
authors.forename: Jane S
authors.initials: JS
authors.lastname: Hocking
authors.forename: Matthew
authors.initials: M
authors.lastname: Law
authors.forename: Sandra
authors.initials: S
authors.lastname: Walker
authors.forename: Sepehr N
authors.initials: SN
authors.lastname: Tabrizi
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Fairley
authors.forename: Catriona S
authors.initials: CS
authors.lastname: Bradshaw
mesh_terms: D003267:Contraception / Q000379:methods*; D005260:Female; D006728:Hormones / Q000378:metabolism*; D006801:Humans; D015995:Prevalence; D012306:Risk; D016585:Vaginosis, Bacterial / Q000453:epidemiology / Q000517:prevention & control*
chemical_list: D006728:Hormones
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