Chlamydial infection among females attending an abortion clinic: prevalence and risk factors.

To determine the prevalence of Chlamydia trachomatis infection and the epidemiologic risk factors for chlamydial infection in the Quebec City region, screening was done with an enzyme immunoassay in 920 females who attended an abortion clinic between November 1985 and June 1986. The organism was detected in 105 (11.4%) of the patients. After adjustment for confounding variables, four variables were found to be independent risk factors for chlamydial infection: age 24 years or less (prevalence ratio 3.0 [p less than 0.001]), two or more sexual partners during the previous year (prevalence ratio 1.8 [p = 0.001]), no contraception or the use of a nonbarrier method (prevalence ratio 1.9 [p = 0.030]) and living in an urban area (prevalence ratio 1.6 [p = 0.046]). The results confirm that chlamydial infection is prevalent in this population. The identified risk factors may prove useful in determining the target population for screening programs.