Well, I'm not female, or pregnant, nor have I ever had a girlfriend, or close friend who's been pregnant, so my experience on this is a little shaky, but as far as I know, the only thing alcohol is good for (biologically speaking) is killing things. What I mean by that is that other than getting humans drunk, alcohol kills basically everything that tries to exist in it (bacteria, insects, and I'm sure you could kill the F--- out of a small mammal by dunking it in some 40%), so it seems counter-logical to me to basically saturate a small, fragile developing human in what amounts to death-in-a-glass.
And yes, small amounts of wine sound like it wouldn't do any harm, but if I was pregnant(hypothetical) or had a woman who was pregnant (also hypothetical), I would feel that any alcohol is too much, simply because that the line of "too much alcohol" is hard to find even when there isn't a little person growing inside of you, much less than when there is another life depending on your responsibility.
And yes, small amounts of wine sound like it wouldn't do any harm, but if I was pregnant(hypothetical) or had a woman who was pregnant (also hypothetical), I would feel that any alcohol is too much, simply because that the line of "too much alcohol" is hard to find even when there isn't a little person growing inside of you, much less than when there is another life depending on your responsibility.