Barrier methods of contraception and the risk of cervical neoplasia.

The relationship between the use of barrier contraception methods and the risk of cervical neoplasia was analyzed using data from a case-control study conducted in the greater Milan area, northern Italy. A total of 367 cases of invasive cancer under 60 years of age were compared with 323 subjects in hospital for acute conditions unrelated to any of the established or suspected risk factors for cervical cancer, and 316 cases of cervical intraepithelial neoplasia were compared with 258 outpatient controls. Ever-use of barrier methods (condom and diaphragm) was reported by 6% of the cases of invasive cancer and 12% of hospital controls. Corresponding values for intraepithelial neoplasia were 16% for cases and 22% for outpatient controls. Considering the total use of barrier methods, compared to never use, the relative risk of invasive cervical cancer was 0.4 (95% confidence interval 0.2-0.9) and decreased with duration of use (chi 2(1), trend = 5.18, p = 0.02). Likewise, use of barrier methods lowered the risk of intraepithelial neoplasia; the estimated relative risks were 0.9 in users for less than two years and 0.6 for two or more (chi 2(1), trend = 4.61, p = 0.03). Although the protection for invasive cancer appeared to be greater at older ages and in multiparous women, the relative risks were not significantly heterogeneous in various strata of parity, number of sexual partners, oral contraceptive use and history of Pap smears.