New findings suggest that bacterial vaginosis increases the risk for miscarriage after 13 weeks of gestation but not before, according to a report in the December 7, 2002, issue of the British Medical Journal. The study involved 1216 pregnant women, 174 of whom had bacterial vaginosis. A total of 121 women experienced miscarriages before 16 weeks of gestation.

Women with bacterial vaginosis had a 1.15 relative risk for miscarriage before 16 weeks, compared with women who were not infected. Further analysis, however, showed a particularly high relative risk (3.45) for miscarriage between 13 and  15 weeks of gestation.