There was a news article a while back (6mths maybe) that said a study showed drinking any alcohol during pregnancy can lower the babies IQ levels and should be avoided completely. Although the study only looked at children up to 3 years old.
I've had one glass of Buck's Fizz (and wished I didn't as the orange was far to acidic for me at the time). Other than that I've abstained completely - partly health partly as I'd end up wanting more than one.
There's some ok alcohol free wine out there and I'm really into Beck's Blue lager - especially in the sunshine