Vitamins and cycles?

[BrittBS]

So before I had my daughter (5 years ago) I had a 28 day cycle, never failed, I even knew down to the hour when I would start! After I had her I had the mirena IUD and bled randomly, for weeks at a time with only a few days in between. It was awful. I finally had it removed after 2 years and ever since my cycles have been 27-35 days. I started taking prenatal vitamins when we started TTC. Since then my last three cycles have been 28 days. Is this a coincidence or could the vitamins and stuff have helped regulate me again??