Which one of the following is the best drug of choice for treatment of bacterial vaginosis during pregnancy

Although no drug is considered absolutely safe in the first trimester , there is a relative safety of usage of class 'B' drugs in pregnancy. Metronidazole comes under that class where the drug is safe in animal studies and also in most human studies. If given a choice, its prudent to use an absolute safe agent like betadine vaginal pessary which will buy time till the patient is in the second trimester for safe usage of category B or even C category drugs.