I had the occasional glass of wine or champers after my first trimester with both my boys. I actually asked my Ob when pg with DS1 what she thought and her words were "there's no evidence to suggest an occassional glass causes any harm to the baby, but no evidence to suggest it doesn't either. I think a glass every now and then is ok - just use your commonsense". Her words exactly.

I think be guided by how YOU feel about it. If you're going to enjoy your glass for your birthday guilt-free, then do it. But if you'll beat yourself up then there's no point.
If it were me, I'd have a glass to celebrate my birthday ... but that's me