Cervical carcinoma and reproductive factors: collaborative reanalysis of individual data on 16,563 women with cervical carcinoma and 33,542 women without cervical carcinoma from 25 epidemiological studies

Int J Cancer. 2006 Sep 1;119(5):1108-24. doi: 10.1002/ijc.21953.

Abstract

The International Collaboration of Epidemiological Studies of Cervical Cancer has combined individual data on 11,161 women with invasive carcinoma, 5,402 women with cervical intraepithelial neoplasia (CIN)3/carcinoma in situ and 33,542 women without cervical carcinoma from 25 epidemiological studies. Relative risks (RRs) and 95% confidence intervals (CIs) of cervical carcinoma in relation to number of full-term pregnancies, and age at first full-term pregnancy, were calculated conditioning by study, age, lifetime number of sexual partners and age at first sexual intercourse. Number of full-term pregnancies was associated with a risk of invasive cervical carcinoma. After controlling for age at first full-term pregnancy, the RR for invasive cervical carcinoma among parous women was 1.76 (95% CI: 1.53-2.02) for > or => or =7 full-term pregnancies compared with 1-2. For CIN3/carcinoma in situ, no significant trend was found with increasing number of births after controlling for age at first full-term pregnancy among parous women. Early age at first full-term pregnancy was also associated with risk of both invasive cervical carcinoma and CIN3/carcinoma in situ. After controlling for number of full-term pregnancies, the RR for first full-term pregnancy at age <17 years compared with > or => or =25 years was 1.77 (95% CI: 1.42-2.23) for invasive cervical carcinoma, and 1.78 (95% CI: 1.26-2.51) for CIN3/carcinoma in situ. Results were similar in analyses restricted to high-risk human papilloma virus (HPV)-positive cases and controls. No relationship was found between cervical HPV positivity and number of full-term pregnancies, or age at first full-term pregnancy among controls. Differences in reproductive habits may have contributed to differences in cervical cancer incidence between developed and developing countries.

Publication types

  • Comparative Study
  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Carcinoma / epidemiology*
  • Carcinoma / physiopathology
  • Case-Control Studies
  • Cervical Intraepithelial Neoplasia / epidemiology
  • Cohort Studies
  • Female
  • Humans
  • International Cooperation
  • Parity
  • Pregnancy
  • Reproduction*
  • Risk Assessment
  • Risk Factors
  • Uterine Cervical Neoplasms / epidemiology*
  • Uterine Cervical Neoplasms / physiopathology
  • World Health Organization