Objectives The association between Mycoplasma genitalium (M. genitalium) serum antibodies and infertility in women and men, as well as infertility subtypes, was investigated.

Methods Stored serum was obtained from two patient cohorts: infertile couples (239 women and 243 men) attending a gynaecological outpatient clinic between October 1997 and February 2001 and 244 age-matched spontaneously pregnant women. An enzyme immunoassay was used to detect serum immunoglobulin G (IgG) antibodies to M. genitalium in these samples. Patient's Chlamydia trachomatis seropositivity had been previously determined. Risks were calculated using multivariate logistic regression.

Results M. genitalium serum IgG was more common among women of infertile couples (5.4%) than among fertile controls (1.6%) (OR (95%CI) 3.45 (1.10 to 10.75)), adjusting for C. trachomatis IgG (adjusted OR=3.00 (0.95 to 9.47)). Of the women with tubal factor infertility (TFI) 9.1% had M. genitalium IgG compared with 4.6% of women without TFI (OR=2.07 (0.60 to 7.05)); (AOR=1.20 (0.32 to 74.40)). In patients IgG positive to both microorganisms the OR for having TFI was increased (OR=4.86 (1.22 to 19.36)) compared with those positive to C. trachomatis IgG only (AOR=3.14 (1.58 to 6.20)). No associations were found with other infertility diagnoses. Only two men of the infertile couples were M. genitalium IgG positive (0.8%).

Conclusions M. genitalium serum IgG was associated with infertility in women, however insignificant after adjustment for C. trachomatis IgG, but not with infertility subtypes within this study. M. genitalium IgG seroprevalence among men was very low and not associated with male factor infertility.