The impact of oral contraception on chlamydial infection among patients with pelvic inflammatory disease.

The prevalence of oral contraceptive use in association with chlamydial pelvic inflammatory disease (PID) and the presence of anti-chlamydial IgG and IgA in a population of 144 hospitalized and outpatient subjects with a standard diagnosis of PID was studied. The rates of chlamydial PID and IgA detection were 15.3% (22/144) and 13.9% (20/144), respectively. After stratification for age, number of pregnancies, and lifetime sexual partners, the rates of chlamydial PID (odds ratio = 0.30, 95% CI = 0.10 - 0.89) and IgA detection (odds ratio = 0.23, 95% CI = 0.07 - 0.73) were lower among previous or current oral contraceptive users than in women who had never used birth control methods. Analyses of linear trend indicated a negative association between increasing duration of exposure to hormonal contraception and anti-chlamydial IgG and IgA. This study confirms that among patients with chlamydial PID, the frequency of oral contraceptive use is lower than that in patients with PID of other etiology. Serologic studies suggest a possible relationship between hormonal contraception and changes in immune response or susceptibility to chlamydial infection.