Sexually transmitted diseases and tubal pregnancy.

The risk of tubal pregnancy associated with seropositivity to Chlamydia trachomatis or following a diagnosis of gonorrhea, genital herpes, trichomoniasis, genital warts, or nonspecific vaginal infection was evaluated in a study of this condition among women who were members of a prepaid health plan. A total of 264 women who had a tubal pregnancy between 1981 and 1986 were interviewed about their history of these sexually transmitted diseases (STDs). Their responses were compared to those of 715 women who were matched by age and county of residence but were otherwise randomly selected from the enrollment files of the health plan. Chlamydia antibody status was known in a sample of 135 cases and 192 controls. Although more cases reported a history of gonorrhea, trichomoniasis, and non-specific vaginal infections than did controls, only a modestly elevated risk for trichomoniasis remained after logistic regression was used to adjust for the effects of age, reference year, race, presence of contraception at reference date, seropositivity to Chlamydia trachomatis, and a history of other STDs. By contrast, among women for whom Chlamydia trachomatis antibody status was assessed, presence of antibody was associated with a two-fold increase in the risk of tubal pregnancy after adjusting for the effects of the previously enumerated variables. These findings confirm the relevance of Chlamydia trachomatis as a risk factor for ectopic pregnancy, and they also underscore the importance of adjustment for the influence of other STDs when evaluating the association between a specific STD and the occurrence of tubal pregnancy.