A new study has found that women who have had chlamydia are at greater risk of an ectopic pregnancy because of a lasting effect of the infection.
The research provides evidence for the first time of how chlamydia can increase the risk of an ectopic pregnancy.
University researchers found that women who had had the sexually transmitted infection were more likely to produce a particular protein in their Fallopian tubes.
Increased production of this protein - known as PROKR2 - makes a pregnancy more likely to implant in the Fallopian tube.
The infection is known to cause infertility as it can lead to scarring and blockages in the Fallopian tube.
The study has been published in the Americal Journal of Pathology.