0.25 Xanax when I was 3 weeks?

I am freaking out, but at the time when I was technically 3 weeks pregnant, I took a low dose xanax. Is this something I should be concerned about? I take it very rarely in general so this is no dependency. Google didn't help put me at ease when I saw some results that suggested possible birth defects. Should I be worried about the risk of taking this so early on?