Relation between antibodies to Chlamydia trachomatis and spontaneous abortion following in vitro fertilization

Many couples undergo in vitro fertilization due to occlusion of the fallopian tubes. Chlamydia trachomatis infections are a major cause of this tubal damage. Since this organism has also been associated with poor pregnancy outcome, we investigated whether a past exposure to C. trachomatis was associated with spontaneous abortion following in vitro fertilization and embryo transfer.

Sera from 145 women undergoing IVF were diluted 1:128 and tested for IgG antibodies to C. trachomatis by an immunoperoxidase assay, using infected cells fixed to slides. All subjects and their partners were negative for C. trachomatis by culture or by DNA hybridization.

Serological evidence of a past chlamydial infection was observed in 33.8% of the women. The incidence of antichlamydial IgG was greater (P less than 0.001) in women whose infertility was due to known tubal disease (37 of 78; 47.4%) than in women whose infertility was due to other causes (12 of 67; 17.9%). Spontaneous abortions after embryo transfer occurred in 20% of the subjects. The incidence of antichlamydial IgG in aborting women (20 of 29; 69.0%) was greater (P less than 0.001) than the incidence in either women with successful pregnancies (9 of 38; 23.7%) or women who did not become pregnant (20 of 78; 25.6%) after IVF. No relation was observed between antichlamydial antibody status and maternal age, the number of oocytes aspirated, the number of oocytes fertilized, and the number of embryos transferred.

A previous infection with C. trachomatis may increase susceptibility to subsequent spontaneous abortion, even in the absence of a detectable current infection.