I'd guess it would reflect poorly, but I don't think the grades themself will be your biggest obstacle. Leaving after a semester implies you are unsure of your goals, and your motivation for an mba will be questioned. That should be your bigger focus. Assuming you can reasonably articulate the reason you want the mba and decided law isn't for you, I wouldn't be concerned with the grades.
If you are a 1l, I'd recommend applying to the 4 year jd/mba program rather than dropping out (assuming you value the dual degree). That's just my opinion though - I know the 1l exam jitters and would at least recommend you think about this after exams are over.
Good luck.Posted from my mobile device