Speaking of embryonic stage--there is no placenta until somewhere in the 4th week when the tissue begins to form, then there's virtually no exhange going on until after week 6, and full placental function only takes over well after week 8 (when fetus status is conferred). So all that talk about total alcohol avoidance early (at least *really early*) is cultural paranoia which has zero basis in fact..
I drank until week 6... but it's weeks 6 - 10 or so when the face really starts to take shape and since that's the physical things they look for in FAS, that's why I avoid in the first tri. But not after that.
May be no scientific basis for it... but sure makes me feel better.