I think it is just whatever you are personally comfortable with. Historically, there are periods when it was safer to drink meed then the local water supply. And also recent research supports moderate drinking:
But really it is whatever you are comfortable with. With a highly medicalized version of pregnancy, where a woman is treated as a an object and not an agent, we were told "never drink! during pregnancy" because we didn't know what was good for the baby. And women couldn't possibly enjoy themselves, right? But the *science* (per the link above) shows that there is no harm, and it might actually be beneficial. So rather then treating pregnant women as children who cannot decide how much to drink during pregnancy, I think it is treating woman as adults and allowing them to chose to have a glass of wine now and then. No big deal.
"The study, which found no evidence of harm from having a couple drinks a week during pregnancy, was so well done and its findings so conclusive that it ought to become the final word in the field, said Fred Bookstein, an applied statistician who studies fetal alcohol spectrum disorders at both the University of Washington, Seattle, and the University of Vienna"
Of course it is always best to ask you care provider if you have a specific question. But you body naturally produces a small amount of alcohol, and the majority of alcohol is metabolized and doesn't reach the baby. And binge drinking (pregnant or not) is always wrong.
I understand where you are coming from--with my first pregnancy I was so worried about doing something wrong, etc. But really, I think parenting and birth and labor is about trusting yourself and your body, and not what people tell you.... So if research supports having a glass of wine now and then, and I want to have a glass of wine now and then, so be it. :)