The international research team base their conclusions on long term monitoring of almost 44,000 women aged 15 to 24 between 1985 and 1989.
The women were taking part in the Swedish Uppsala Women's Cohort Study, which links information from laboratory, hospital, and population registers.
The women's reproductive health was tracked up to the end of 1999, and a cumulative rate calculated for a hospital diagnosis of pelvic inflammatory disease (infection of the fallopian tubes), ectopic pregnancy (a fertilised egg implanting in the fallopian tube), or infertility.
All of these conditions can be caused by the sexually transmitted infection Chlamydia trachomatis.
The researchers found that although testing positive for Chlamydia increased the chances of all these conditions, the rates were not as high as the results of earlier studies had suggested.
The rate of pelvic inflammatory disease or PID was just under 4% by the age of 35 across the entire group. In those who had tested positive for Chlamydia, this figure rose to 5.6%.
The rate was 4% in women who had tested negative and just under 3% in those who had never been screened.
Similarly, the overall rate of ectopic pregnancy was 2.3%, rising to 2.7% in those testing positive for Chlamydia. It was 2% for those testing negative for the infection and just under 2% for those who had never been screened.
For infertility, the rate was just over 4% for the entire group and 6.7% for those testing positive for Chlamydia The rate was 4.7% for those testing negative and just over 3% for those who had never been screened.
The researchers comment that the rate of severe complications as a result of Chlamydia infection seems to be lower than expected, suggesting that the predicted benefits of current screening programmes "might have been overestimated."
"A low incidence of Chlamydial complications is good news for individual patients, but raises questions about the presumed cost effectiveness of current Chlamydia screening programmes," they conclude.
They point out that most economic evaluations of these programmes assume uptake of 60 to 100%, but in practice uptake is often lower. Research is also now beginning to suggest that in half of symptomless patients, the infection resolves by itself within a year without doing any damage.
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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