The authors are not clear how this condition affects miscarriages. Dr Janet Wilson, a consultant physician specialising in genito-urinary medicine, said it was possible that the infection caused endometritis, an inflammation of the uterus. One of those chemicals, tumour necrosis factor alpha, causes the blood vessels to constrict, effectively starving the fertilised egg of vital nutrients. The way that bacterial vaginosis is transmitted is unclear. Some believe it can be passed on through sexual activity, although the organisms responsible also have been found in young women who are not sexually active.
Many women carry the bacteria which cause the infection, but at low levels which pose no risk.
Dr Wilson said women who planned to get pregnant should seek medical advice about the infection, which is easily treatable with antibiotics. The BBC is not responsible for the content of external internet sites.