http://www.marchofdimes.com/professionals/681_1170.asp

From March of Dimes (non-for profit organization in the US for saving children/preventing birth defects). That should answer all questions re. pregnancy and alcohol. It also says that even as little as one drink a week has been shown to cause behavioural problems and lower intelligence in children.

I'm sorry - I feel very passionately about not drinking at all during your pregnancy (at least after you know you are pregnant).