I think it depends on what stage of pregnancy & how much. Early on, first tri, I would avoid it; I think one drink later would be ok?
Having said that I got married at 10 weeks & had a small glass (actually it was a wine cooler thing); I checked with my doctor & she was fine with it.
The whole thing about avoiding it altogether is because they don't know how much is ok; so it's safer (and easier) to just say 'none at all'.
I guess you will get a lot of different opinions.... My mother was advised by her doctor, late in her pregnancy that a glass of wine would be a good thing if it relaxed her (that was in the 70's, FWIW)