Never used them when pregnant but before I have many times and they worked perfect tell I could see a doctor
Ithey are better for preventing, there is another kind that is more concentrated that if its not too bad yet use with some black cherry or real cranberry juice. Id ask the pharmasist about the more concentrated kind.
When I was younger I got uti quite frequently and could feel them coming on and I would start taking double the amount of azo cranberry pills long with black cherry juice and that usually would wipe it out.
If its bad already its probably too late for those things. If you get antibiotics make sure you ask about some probiotics because then you could just get a yeast infection or something else.
I know they are supposed to prevent them, but I don't think they treat them. You'll need antibiotics.