BERKELEY, CA (UroToday Inc.) - Dr. Karinen and colleagues from Finland and the United Kingdom performed a nested-case controlled study to investigate the association between serum antibodies to Chlamydia trachomatis and fertility. They used data from the Northern Finland Birth Cohort 1966 (NFBC 1966), which included 12,231 persons from the two northern most provinces of Finland, who were born in 1966. They used the time to pregnancy in months (TTP) as a marker for fertility. Subfertility was defined as a TTP of 12 months or more. Their findings were published in the October 2004 edition of Epidemiology and Infection.

Subjects for the study were obtained from 4158 persons in the database who had information on TTP of the fist pregnancy and from 414 who had been trying to conceive with no prior pregnancies by the age of 31. There were two randomized controls who had TTP less than twelve months compared to every subfertile patient. In the final analysis there were 479 cases and 967 controls. Variables measured included the presence of C. trachomatis antibodies, and self reported, physician diagnosed and confirmed history of C. trachomatis infection or pelvic inflammatory disease. All serum samples were screened for the presence of C. trachomatis IgG antibodies. All positive samples were then further studied using microimmunofluorescence testing using immunotype pools and individual immunotypes.

Of the 479 cases, 298 were female and 181 males. 53% (159/298) of the women and 51% (93/181) of the men reported that they themselves, their partner or both, had been examined for infertility. In 48% of these cases, no reason for infertility was found. By age 31, 75% of the studied cases had finally had children of their own.

There was no difference in the incidence of reported genital infections between cases and controls. Screening for C. trachomatis IgG antibodies was positive in 14.4% of male cases and 9.3% of controls, and 16.8% of female cases and 14.8% of controls. The analysis of serovar pool-specific C. trachomatis with the largest difference between cases and controls was found in antibodies against C complex containing immunotypes C,J,H, and I in 7.7% of male cases and 3.0% of their controls (P=0.012). Among single serotypes the IgG antibody types which were significantly higher in cases than controls were H among the males, and C,J,H, and I among females. C. trachomatis antibodies were more often seen in both males and females reporting a previous history of C. trachomatis infection.

With these findings, the authors conclude that there is a positive association between C. trachomatis infection and subfertility. They also suggest that serology may be useful in screening for this type of infertility.

Epidemiol Infect 2004; 132:977-984