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).Conclusion:Childbirth increases the risk for subsequent CIN3+ among women with persistent HPV infection.

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In this nationwide survey, a significant decline in the prevalence of primiparous women who smoked during pregnancy was observed from 1997 to 2005. Despite of this, pregnancy-related smoking prevalence in Denmark is still higher than in the other Nordic countries. Furthermore, the proportion of pregnant smokers was highest among young women, and future smoking cessation programs should bring this subgroup of women into focus.

Young age at first intercourse is associated with subsequent risk-taking behaviours. Our study emphasizes the importance of targeting prevention efforts towards the complexity of risk-taking behaviours.

Women who received the HPV vaccine before or at the same age as sexual debut did not subsequently engage more in sexual risk taking behaviour than women who did not receive the HPV vaccine.

Background Smoking has been associated with cervical cancer. We examined whether smoking increases the risk for high-grade cervical lesions in women with high-risk human papillomavirus (HPV) infection. Methods In a population-based cohort study, 8,656 women underwent a structured interview, and subsequently cervical cells were obtained for HPV DNA testing. Women with high-risk HPV infection and no prevalent cervical disease at baseline (n=1,353) were followed through the Pathology Data Bank for cervical lesions for up to 13 years. Separate analyses of women with persistent high-risk HPV infection were also conducted. Hazard ratios (HRs) for a diagnosis of cervical intraepithelial neoplasia grade 3 or worse/high-grade squamous intraepithelial lesions or worse (CIN3+) and the corresponding 95% confidence intervals (CIs) were calculated in the 2 groups. Results Among high-risk HPV positive women an increased risk for CIN3+ was associated with long-term smoking (≥10 years) and heavy smoking (≥20 cigarettes/day). In the subgroup of women with persistent HPV infection heavy smoking was also associated with a statistically significantly higher risk for CIN3+ than never smoking (HR, 1.85; 95% CI, 1.05–3.22, adjusted for length of schooling, parity and HPV type at baseline). The average number of cervical cytology screening tests per year during follow-up did not explain the differences in risk in relation to smoking (p=0.4). Conclusions Smoking is associated with an increased risk for subsequent high-grade cervical lesions in women with persistent high-risk HPV infection. Impact Our study adds to the understanding of the role of smoking in the natural history of HPV and cervical carcinogenesis.

Repeated CT infections increased the risk of CIN3+ among women with prevalent as well as persistent high-risk HPV infection.

These measurements of sexual behavior before the introduction of national human papillomavirus vaccination programs will form the basis for a comparison with a similar survey performed after vaccination has been introduced.