title: Parity as a cofactor for high-grade cervical disease among women with persistent human papillomavirus infection: a 13-year follow-up.
abstract: BACKGROUND
  Several environmental factors have been associated with increased risks for cervical cancer. We examined whether reproductive history, contraceptive use, or sexual behaviour increase the risk for cervical intraepithelial neoplasia grade 3 or worse (CIN3+) among women with persistent human papillomavirus (HPV) infection.
  
  
  METHODS
  A population-based cohort of women participated in a personal interview and underwent a gynaecological examination at which cervical specimens were obtained for HPV DNA testing. Follow-up information (~13 years) on cervical lesions was obtained from the Danish Pathology Data Bank. Women who had a high-risk HPV infection comprised the overall study population (n=1353). A subgroup of women with persistent high-risk HPV infection (n=312) was identified. Hazard ratios (HRs) for a diagnosis of CIN3+ and the corresponding 95% confidence intervals (CIs) were calculated.
  
  
  RESULTS
  Women with persistent HPV infection who had given birth had a significantly increased risk for CIN3+ (HR=1.78; 95% CI: 1.07-2.94). No association was found with pregnancy, use of intrauterine devices, or sexual behaviour. Based on small numbers, women with persistent HPV infection had a decreased risk for CIN3+ with any use of oral contraceptives (HR=0.54; 95% CI: 0.29-1.00).
  
  
  CONCLUSIONS
  Childbirth increases the risk for subsequent CIN3+ among women with persistent HPV infection.
authors.affiliation: Danish Cancer Society Research Center, Strandboulevarden 49, 2100 Copenhagen Ø, Denmark.
authors.forename: K E
authors.initials: KE
authors.lastname: Jensen
authors.forename: S
authors.initials: S
authors.lastname: Schmiedel
authors.forename: B
authors.initials: B
authors.lastname: Norrild
authors.forename: K
authors.initials: K
authors.lastname: Frederiksen
authors.forename: T
authors.initials: T
authors.lastname: Iftner
authors.forename: S K
authors.initials: SK
authors.lastname: Kjaer
mesh_terms: D000293:Adolescent; D000328:Adult; D003267:Contraception; D004279:DNA, Viral / Q000032:analysis; D005260:Female; D006801:Humans; D027383:Papillomaviridae; D030361:Papillomavirus Infections / Q000150:complications*; D010298:Parity; D012725:Sexual Behavior; D002583:Uterine Cervical Neoplasms / Q000821:virology*; D055815:Young Adult; D002578:Uterine Cervical Dysplasia / Q000821:virology*
chemical_list: D004279:DNA, Viral