Hmm, I think it's probably a good bet that medical conferences are more well-dressed than scientific ones! So I'm not sure I can really give you good advice, but I'd say maybe your regular dresses plus a blazer or two? If it turns out to be more casual you can lose the blazer. Blazer/jacket/cardi is a good idea anyway because it always seems to be freezing at these things.
Here is what I wore to a scientific conference (in DC, at a nice hotel). I was definitely one of the more dressy people there. It was summer and very hot. In cooler weather I'd probably go for trousers or skinny black pants, or skirts w/tights. And boots or booties. At scientific conferences you could definitely wear jeans too... maybe not ripped up ones but plain dark ones would be perfectly appropriate. I'm guessing your conferences are dressier - so maybe take my capsule and bump everything up a notch. So real blazer instead of knit blazer, for example. Or dressier shoes instead of the funky gladiators.
http://youlookfab.com/welookfa.....el-capsule
I feel like when meeting scientists/academics, you don't want to look too "business" because that's kind of seen as anti-academic, you know? But I don't think there is this bias in medicine?