Chlamydia is the most common, curable, bacterial, sexually-transmitted infection in the UK. Last year there were almost 104,000 cases in genito-urinary clinics alone. The number of sexually active people under 25 infected with Chlamydia is now thought to be just under half a million - about one in ten.
It often has no obvious symptoms. But if it is left untreated it can lead to severe complications. It is widely believed to cause Pelvic Inflammatory Disease (PID) and sometimes infertility in women, and in men it can lead to inflammation of the testicles and sperm conducting tubes, and affect joints.
But in August 2005 Lord Robert Winston suggested the link between Chlamydia and infertility was not clear. He said:
"I think the evidence that Chlamydia affects fertility is very dubious. Most infertility is not due to Chlamydia. I haven't seen any figures that demonstrate that it is causing infertility. The link between Chlamydia and tubal disease is based on only two papers written in Sweden in the Sixties and it has never been checked. There's no British data." (1)
But there is little room for doubt according to Professor Bill Ledger, a consultant at Sheffield's Royal Hallamshire hospital and one of the UK's leading infertility specialists. In Sheffield, he and his three colleagues treat around 100 women a year who are experiencing problems due to Chlamydia. Nationally, he believes that up to a third of all IVF treatments are because of the damage caused by Chlamydia - that's somewhere between 5,000-10,000 couples.
Professor Bill Ledger believes Chlamydia affects fertility
It's believed that the Chlamydia infection damages the hairs along the fallopian tubes which help the egg travel from the ovaries to the womb. This damage can lead to scarring, which in turn leads the tubes to be blocked. (2)
Women with damaged tubes do occasionally fall pregnant but there is an increased risk of the pregnancy developing in the tubes rather than the womb. This is called an ectopic pregnancy. The tube can split apart causing serious pain and bleeding. This is an emergency because the bleeding can be life threatening. (2)
One of the key papers, "Chlamydia and its effect on reproduction (1996)" by L.V. Westrom measured the likelihood of infertility after episodes of Chlamydia. His research found that 79 out of 1025 women (7.8%) were infertile because of post-salpingitic tubal occlusion compared with a control group where the incidence was just 0.9%.
The paper also measured the relative risk (RR) of infertility when considering the number of episodes of Chlamydia. It was 1% with no episodes, 5% after one episode, 11.3% after two episodes and 19.8% after three episodes
There is also evidence showing a relationship between Chlamydia screening and a fall in genital tract infections and pelvic inflammatory Disease amongst women. In Sweden in 1985 a Chlamydia screening programme was introduced across the country in a variety of health settings - including primary care (such as GPs) and at specialist clinics (such as GUMs). Rates of testing increased from 1985 to 1991 and a corresponding decrease occurred in the number of cases diagnosed. In one county the number of cases had falled to 40% of initial levels. (4)
In Wisconsin (USA), a state wide initiative in 1986 used risk factors to determine who should be screened. By 1990 a 53% decrase in prevalence was seen.4 In one randomised controlled trial of 2607 women, the number of Pelvic Inflammatory cases fell by 56%. (5)
1. London Evening Standard interview, 9 August 2005
2. Netdoctor.co.uk, written by Dr Angela Robinson, President of BASHH (British Association of Sexual Health and HIV)
3. Herrmann B Johansson A, Mardh P-A. A retrospective study of efforts to diagnose infections by Chlamydia trachomatis in a Swedish county. Sex Transm Dis 1991; 18:233-7
4. Adiss DG Vaughn ML, Ludka D, Pfister J, Davis JP. Decreased prevalence of Chlamydia trachomatis in a Swedish county. Sex Transm Dis 1993;20:28-34
5. Scholes D Stergachis A, Heidrich F Andrilla H, Holmes KK, Stamm W Prevention of pelvic inflammatory disease by screening for cervical chalamydial infections. N Eng J Med 1996;334:1362-6