Antibodies to Chlamydia trachomatis and risk for tubal pregnancy

We performed a case-control study of the effect of exposure to Chlamydia trachomatis on the risk for tubal pregnancy. Sixty women with tubal pregnancies and 60 matched control women with normal second-trimester intrauterine pregnancies were studied. Cases were more likely than controls to have detectable antichlamydial IgG antibodies (82% versus 58%, p < 0.01) and their mean titers were higher. The prevalence of IgM antibody seropositivity was not different between cases and controls (20% versus 12%, not significant). Compared with women with IgG antibody titers of ⩽1:8 the relative risk for tubal pregnancy for women with titers ⩾1:128 was 6.6 (95% confidence interval, 2.0 to 21.6). Among women with tubal pregnancies, antichlamydial antibody titers of ⩾1:128 were significantly associated with pelvic adhesions and inflammatory tubal mucosal damage. Only 17.6% of women with detectable antichlamydial antibody or inflammatory tubal damage reported a history of pelvic inflammatory disease or gonorrhea.