The most common sexually transmitted infection might cause infertility in men as well as long-term health problems for women, researchers said last night.
The chances of couples achieving a pregnancy after fertility treatment may be cut by a third if the man is infected by chlamydia, a Swedish study suggests, after analysis of the progress of couples for an average of more than three years.
The exact reasons for the infertility in men are still unclear, although sperm motility is a possible factor being studied by the research team.
Although men can experience sharp burning and itching in their genitals, most evidence of infertility has so far been connected to women, because of the danger of their developing pelvic inflammatory diseases that can damage the fallopian tubes.
Chlamydia is diagnosed in 35,500 men and 45,500 women in England and Wales each year, doubling the figures from 1997. Many cases are not detected, largely because symptoms are often absent in people carrying the bacterium.
This problem has already led to an NHS screening programme for the disease, which is often easily treated by antibiotics. Young women under 25 are the initial focus because of the perceived greater health consequences for them. But there is growing recognition of the need to reach sexually active men, who are less likely to come forward. Pilot schemes promoting sexual health are running at colleges, nightclubs, sports clubs, workplaces and military bases.
The Swedish researchers, who report their findings in the journal Human Reproduction, tested 244 couples at a fertility clinic. They looked for antibody markers for previous or persistent chlamydia infection. When they found antibodies, they tested for chlamydia DNA, the presence of which would suggest continuing active infection. Fertile women who had conceived before were also tested.
Among infertile couples who tested positive for antibodies, 6.8% of women and 7.1% of men carried chlamydia DNA in their urine.
Jan Olofsson, the head of the research team, said the increased prevalence of antibodies in infertile couples had been expected, but "our findings show that it is not only women who need to be concerned about contracting chlamydia. Men need to be aware it is potentially serious for them as well."
But the presence of antibodies in men was not related to tubal factor infertility in women, suggesting other factors were involved. "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."
A follow-up study on semen analyses is near completion.
There was reassuring news from the study. Among those couples who attended the fertility clinic and became pregnant, either spontaneously or through IVF, infection or the presence of chlamydia antibodies did not put the pregnancy at risk. There was no difference in pregnancy outcomes between those couples who had tested positive for antibodies and those who had not.
