A team from Umeå University Hospital in Umeå and the Scandinavian Fertility Center in Gothenburg, found decreased pregnancy rates in couples where the man had IgG antibodies - a marker of previous or persistent infection by Chlamydia trachomatis, one of the most common sexually transmitted diseases.
The researchers tested 244 infertile couples attending their infertility clinic for the antibodies. For those couples where one partner was positive they also tested for Chlamydia DNA. They followed the couples' progress for between 14 and 54 months (mean follow-up 37 months). For controls, they tested aged-matched women who had conceived spontaneously. They found IgG antibodies in nearly a quarter of the infertile women, a fifth of the infertile men but only 15.6% of the controls. Among infertile couples with IgG antibodies 6.8% of the women and 7.1% of the men carried Chlamydia DNA in their urine, suggesting active infection. Of the total study group 3.7% exhibited Chlamydia DNA, but the figure was over 13% in the infertile antibody positive couples.
Associate Professor Jan Olofsson, head of the research team, said: "As anticipated, we found a raised prevalence of Chlamydia trachomatis IgG antibodies in the infertile population compared with the proven fertile population. Importantly, as well as the expected finding of antibodies among the female partners we found that antibodies in the male partner was significantly inversely correlated to the overall pregnancy rate. The chance of achieving a pregnancy was reduced by 33% if the man was IgG positive.
"Our findings show that it is not only women that need to be concerned about contracting Chlamydia. Men need to be aware that this is potentially serious for them as well," said Professor Olofsson.
Antibodies in the women were related to tubal factor infertility (TFI) - confirming previous findings that Chlamydia is linked to TFI. But, IgG antibodies in men were not associated with TFI in their partners.
"As there was no connection between IgG antibodies in the men and TFI in their partners there may be alternative or additional mechanisms involved that are reducing fertility. It is possible that decreased sperm motility or concurrent or undetected infection may play a role, but that is speculative as we did not look at these possibilities in the present study," Professor Olofsson said. But, he added, a follow up study on semen analyses was nearing completion.
There was one reassuring finding from the present study. Principal author Dr Annika Idahl said that for those couples attending the fertility clinic who became pregnant, either spontaneously or through IVF, infection or Chlamydia antibodies did not put the pregnancy at risk as there was no difference in the outcome of the pregnancies between IgG positive or negative couples. (150 of the 244 couples achieved pregnancy - 58.7% spontaneously and 41.3% via treatment).
The finding that infection or the presence of Chlamydia antibodies in the infertile men is linked to reduced fertility has lead researchers to suggest screening of both partners who attend infertility clinics. Dr Idahl said: "We suggest that Chlamydia antibody testing of both male and female partners should be included in routine infertility work-up in order to enable a more adequate prognosis for the likelihood of spontaneous pregnancy. But, it remains to be seen in a randomized controlled study whether or not antibiotic treatment either for antibody positive infertile patients or for all infertile patients will increase the chances of pregnancy."
 Demonstration of Chlamydia trachomatis IgG antibodies in the male partner of the infertile couple is correlated with a reduced likelihood of achieving pregnancy. Human Reproduction. Vol 19. No 5. Pp 1121-1126.
 Chlamydia trachomatis: probably the most common sexually transmitted bacterium. A considerable proportion - perhaps half of men and 90% of women - have no symptoms. In women symptoms are often mild but the ascent of the bacterium into the upper genital tract is frequent and leads to pelvic inflammatory diseases with the risk of long term damage to the Fallopian tubes. In men, it may cause non-specific urethritis with discharge and pain on passing urine.
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