I can understand your concern. It has been proved that having Bacterial Vaginitis at the time of pregnancy is associated with the increased risk of a preterm birth and having   a baby of low weight, uterine infection, and preterm premature rupture. It has also been shown that there is a connection between BV and the second part of trimester that can cause even miscarriage. But the reasons why females have bacterial vaginitis give birth to premature babies. It has been found that many women who is having this medical condition seem to deliver normal babies. BV has also been linked to increased chance of pelvic inflammatory diseases and also infections after a surgery related to gynaecology. You can take the relative advice from your gynaecologist and also can check on the same with your GP who will be having a better diagnosis of your condition.