Are you taking macrobid for a uri? I think what is also very often the case with what appears to be spotting during treatment is that the uti in itself can cause what appears to be spotting or a period. https://drhouse.com/can-a-uti-cause-bleeding-like-a-period/ In those cases, it's an inflammatory response. And it gets better when the uti is healed and enough time passes for normalization. The antibiotics kill off bacteria causing the uti which then reduces inflammation. So, I'd say this is a real possibility. I know you posted a link which I opened and read. I guess they are studying it but it does appear to be pretty rare. If you look at that data, it's like 2 patients being looked at in one study and 20 out of 7,500 patients in another for .27 percent (well below 1 percent) of patients on macrobid. So, that doesn't mean it's NOT happening to you but just that you are a rare person. And because it is so uncommon, there's not a lot of data on it. There is another theory as well. Our hormones are touchy. One of the ways that we get an irregular cycle is disruption to the routine such as changes in schedule, weight gain or loss AND illness. How long have you had the spotting and how long ago was the treatment with macrobid?