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Is Bacterial Vaginosis Caused By Sperm?


Updated May 21, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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Question: Is Bacterial Vaginosis Caused By Sperm?
What is bacterial vaginosis, and why does it produce that strange odor after sex?
Answer: It's an overgrowth of certain bacteria normally present at low levels in the vagina. No one is certain exactly what causes BV, or why some women are so susceptible to recurrent bacterial vaginosis, but one thing is for certain... BV stinks! Bacterial vaginosis isn't caused by sperm, but it's easy to understand why some women think it could be. BV symptoms get worse after unprotected sex, because the chemical compounds that cause the odor associated with BV are more noticeable at higher pH. Normally the vagina is mildly acidic, around pH 4. During bacterial vaginosis, the pH increases above 4.5. When semen is present, the vagina actually becomes neutral - pH 7 - and the amines, the chemical compounds that cause the "fishy smell," start to stink. What may be a barely noticeable infection when a woman is not having sex, all of a sudden becomes very obvious when she is, particularly if she doesn't use a condom. That's why many women think that bacterial vaginosis is caused by sex. However, although BV is certainly sexually associated, and made more obvious by sex, ongoing research is geared toward clarifying the role of sex and bacterial vaginosis.

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