Also want to point out: there is a difference between Foetal Alcohol SYNDROME (FAS), and Foetal Alcohol SPECTRUM DISORDER (FASD).
From what I understand, FAS is the more serious and carries physical as well as mental disabilities (including facial as well as brain malformation, and sometimes microcephaly). I work in a school with a child with FAS. It is caused by severe and heavy drinking of the kind associated with alcoholism.
The other: FASD, as the name suggests, encompasses a wide range of severity. FASD has been linked to mild and moderate, to severe and specific learning difficulties, emotional and social developmental problems and behaviour issues in children and adults.
As far as I'm aware, FASD is wildly under diagnosed. We simply do not know to what extent, children with the associated difficulties outlined above, have been damaged by moderate drinking during pregnancy.
There is also no way of telling who is more likely to be affected by certain amounts of alcohol and at what point during pregnancy.
Information on FAS and FASD can be found simply by Googling and clicking on the web pages for a number of different charities that work to raise awareness.
Interesting to note that the charities and organisations that work to promote understanding of both FAS and FASD, advise total abstinence.