Bacterial vaginosis is a condition in which the pH (acid/alkaline balance) and hence the balance of bacteria inside the vagina changes. The vagina contains a mixture of "good" bacteria called lactobacilli, which can help protect against infection (by maintaining a slightly acid pH), and a smaller amount of "bad" bacteria, which can cause infection. What leads to this change or imbalance is not really known but it is quite common. This is not described as a "typical" sexually transmitted infection, but can occur after having unprotected sex with a new partner, rates seem to be higher in women who have multiple sexual partners and lower in women who use condoms. There are, however many other factors that can influence the change in the bacterial environment that are worth considering. These include pregnancy, use of an intrauterine device for contraception, the use of antiseptic or scented soaps in the bath or the use of vaginal deodorants and current smoking habits. Incidence is higher in women who have previously been infected with the human papilloma virus - a group of viruses that can cause genital warts. Bacterial vaginosis may be passed between female partners.
There is evidence that having bacterial vaginosis can increase the risk of catching other sexually transmitted infections including gonorrhoea, chlamydia, genital herpes, human papilloma virus and HIV. This is possibly because the drop in "good" bacteria inside the vagina reduces the protective effects against infection.
The risk of lack of investigation and treatment occurs mainly in pregnancy when complications can include premature birth, miscarriage, rupture of or an infection of the amniotic sac that encloses the baby, or inflammation of the lining of the womb after giving birth called postpartum endometriosis. However pelvic inflammatory disease and infertility risks have been associated with bacterial vaginosis.
The most common symptom is a change in vaginal discharge; this may be a watery, grey or white discharge and may be accompanied by a fishy smell. These symptoms may be most common after sex or after a period. Other symptoms can include pain during intercourse or when passing urine or some light bleeding.
If symptoms are experienced, It is important to get diagnosed quickly to make sure this is not something more serious, exclude other infections and prevent further complications for example in pregnancy. A diagnosis may be made from a description of symptoms or a physical examination. A swab (cotton bud) may be used to take a sample of discharge and cells from inside the vagina. The pH of the vagina may also be measured by taking a swab.
Bacterial vaginosis can be treated with antibiotics. Treatment is effective in 90% of cases. The most commonly used (and preferred) antibiotic is called metronidazole. It is available either as tablets (500mg) taken twice a day for seven days, or as a single larger dose (2g). There are also prescribed vaginal creams that that can be applied each day. Data suggest that the most effective treatment is to take metronidazole over seven days and to complete the full course as prescribed and instructed.
In around a quarter of women who have been successfully treated, bacterial vaginosis may return within one month, over time a high proportion of women may experience further episodes that may require retreatment.