If left untreated, about 10-15% of women with chlamydia will develop pelvic inflammatory disease (PID). In addition Chlamydia can also cause infection of the fallopian tubes, and there might be no symptoms. PID and “silent” infection in these areas may cause permanent damage to the fallopian tubes, uterus, and surrounding tissues. This can lead to infertility.
Most women infected with chlamydia or gonorrhea have no symptoms. It is therefore vital that all sexually active females have at least a yearly screen for Chlamydia and Gonorrhoea and that if positive, that they get treated immediately
Other STIs also affect fertility. In particular we know that HIV can affect semen quality in men, and therefore reduce the chances of a pregnancy. There is of course also the risk that an infected male can pass on the HIV virus to his partner and the mother passing HIV to her baby. It is vital that couples get screened for these and other STI’s such as Hepatitis B and C, prior to trying for a baby. If you are having difficulty conceiving it is recommended to have a set of STI tests performed, just to rule this out as a contributing factor.
I cannot stress enough the importance of asymptomatic screening for STI’s, as an underlying and unnoticed infection can cause lasting damage.