it safe?

I'm 22 weeks pregnant and I was diagnosed with bv at my 20 week scan. Well my dr prescribed metronidazole 500mg twice a day for 7 days. But I've read a lot online that it really isn't safe for pregnant women. That it may cause birth defects. I want to get rid of the infection but I'm scared of it harming my baby. Has anyone had to take this medication? Did it have any effect on the Baby?