title: Oral contraceptive use and uterine leiomyoma risk: a meta-analysis based on cohort and case-control studies.
abstract: OBJECTIVE
  To review the epidemiological and clinical evidence for the association between oral contraceptives (OCs) and uterine leiomyoma (UL).
  
  
  METHODS
  Several databases (Pubmed, Cochrane Central, OVID, SpringerLink, Clinical Evidence, and Google scholar) and reference lists were searched through March 2012 with no restrictions.
  
  
  METHODS
  cohort or case-control studies; the exposure of interest was OCs; the outcome of interest was UL; relative risk (RR) or odds ratio (OR) (or data to calculate them) were reported. Two independent reviewers assessed eligibility criteria and extracted data.
  
  
  RESULTS
  Eleven literatures involving 8,990 UL patients and 1,31,055 participants were included from 3,017 studies initially found. The influence of OCs on UL risk was assessed by comparing "ever", "current" or "former" users and "never" users. Meta-analysis indicated that OCs use did not increase UL morbidity ("ever" vs "never": risk ratio [RR] 0.88; 95 % confidence interval [95 % CI] 0.75-1.04. "current" vs "never": RR 0.43; 95 % CI 0.25-0.73. "former" vs "never": RR 0.96; 95 % CI 0.84-1.08). Dose-response analysis showed the risk of UL morbidity was reduced by 17 % in "ever" users for 5 years or more (P trend = 0.006). However, the results have to be viewed with caution because there was significant heterogeneity (I (2): from 64 to 92 %).
  
  
  CONCLUSIONS
  Although the role of potential bias and evidence of heterogeneity should be carefully evaluated, the present study suggests that UL should not be considered a contra-indication for OCs use.
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Central South University, 110 Xiangya Road, 410078 Changsha, Hunan, People's Republic of China. qinjiabi123@163.com
authors.forename: Jiabi
authors.initials: J
authors.lastname: Qin
authors.forename: Tubao
authors.initials: T
authors.lastname: Yang
authors.forename: Fanjing
authors.initials: F
authors.lastname: Kong
authors.forename: Quan
authors.initials: Q
authors.lastname: Zhou
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D016001:Confidence Intervals; D003276:Contraceptives, Oral / Q000009:adverse effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007889:Leiomyoma / Q000453:epidemiology*; D016017:Odds Ratio; D012307:Risk Factors; D014594:Uterine Neoplasms / Q000453:epidemiology*
chemical_list: D003276:Contraceptives, Oral