title: Role of parity and human papillomavirus in cervical cancer: the IARC multicentric case-control study.
abstract: BACKGROUND
  High parity has long been suspected of being associated with an increased risk of cervical cancer, but previous analyses of this association have not taken the strong effect of human papillomavirus (HPV) into account. To assess the role of reproductive factors in the progression from HPV infection to cancer, we did a pooled analysis including only HPV-positive women.
  
  
  METHODS
  We pooled data from eight case-control studies on invasive cervical carcinoma (ICC) and two on in-situ carcinoma (ISC) from four continents. 1465 patients with squamous-cell ICCs, 211 with ISCs, 124 with adenocarcinomas or adenosquamous ICCs, and 255 control women, all positive for HPV DNA by PCR-based assays, were analysed. We calculated pooled odds ratios by means of unconditional multiple logistic regression models, and adjusted them for sexual and non-sexual confounding factors. The 95% CI were estimated by treating the odds ratio as floating absolute risk.
  
  
  RESULTS
  We found a direct association between the number of full-term pregnancies and squamous-cell cancer risk: the odds ratio for seven full-term pregnancies or more was 3.8 (95% CI 2.7-5.5) compared with nulliparous women, and 2.3 (1.6-3.2) compared with women who had one or two full-term pregnancies. There was no significant association between risk of adenocarcinoma or adenosquamous carcinoma and number of full-term pregnancies.
  
  
  CONCLUSIONS
  High parity increases the risk of squamous-cell carcinoma of the cervix among HPV-positive women. A general decline in parity might therefore partly explain the reduction in cervical cancer recently seen in most countries.
authors.affiliation: Unit of Field and Intervention Studies, International Agency for Research on Cancer, 150 Cours Albert Thomas, F-69372, Cédex 08, Lyon, France. munoz@iarc.fr
authors.forename: Nubia
authors.initials: N
authors.lastname: Muñoz
authors.forename: Silvia
authors.initials: S
authors.lastname: Franceschi
authors.forename: Cristina
authors.initials: C
authors.lastname: Bosetti
authors.forename: Victor
authors.initials: V
authors.lastname: Moreno
authors.forename: Rolando
authors.initials: R
authors.lastname: Herrero
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Smith
authors.forename: Keerti V
authors.initials: KV
authors.lastname: Shah
authors.forename: Chris J L M
authors.initials: CJ
authors.lastname: Meijer
authors.forename: F Xavier
authors.initials: FX
authors.lastname: Bosch
mesh_terms: D000230:Adenocarcinoma / Q000209:etiology / Q000821:virology; D000328:Adult; D002277:Carcinoma / Q000209:etiology / Q000821:virology; D018196:Carcinoma, Adenosquamous / Q000209:etiology / Q000821:virology; D002294:Carcinoma, Squamous Cell / Q000209:etiology / Q000821:virology; D016022:Case-Control Studies; D004279:DNA, Viral / Q000032:analysis; D005260:Female; D020073:Gravidity; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D016017:Odds Ratio; D027383:Papillomaviridae / Q000302:isolation & purification; D030361:Papillomavirus Infections / Q000150:complications*; D010298:Parity; D012307:Risk Factors; D014412:Tumor Virus Infections / Q000150:complications*; D002583:Uterine Cervical Neoplasms / Q000209:etiology* / Q000821:virology
chemical_list: D004279:DNA, Viral