What are the causes for Bacterial Vaginosis?

The reasons for overgrowth of certain types of bacteria in the vagina or an imbalance in the growth of these bacteria are not fully understood. However, certain factors can increase a woman's risk of developing bacterial vaginosis, including:
  • having multiple sex partners,
  • having a female sex partner, and
  • tobacco smoking.
Vaginal douching may also increase the risk of developing bacterial vaginosis. While the condition is more common in women with multiple sex partners, it is not believed to be contagious or entirely related to sexual activity since it is the result of overgrowth or imbalance in the bacteria normally present in the vagina. Moreover, women who have not had sexual activity can develop bacterial vaginosis.

Source: http://www.emedicinehealth.com