Bacterial vaginosis/antibiotics

I'm 30 weeks and just got a positive swab for bacterial vaginosis. My doctor sent in a prescription for metronidazole(antibiotics) but in researching it it says it permeates through the placental membrane and they do not know the effects on the fetus but bv can cause preterm labor or membrane rupture. Only thing is I had strange discharge for 2 days over a week ago(then got tested) and haven't had anything since. Anyone have any experience with this?!