My bad on the title for this post. It's misleading in that it suggests that a baby who doesn't have these facial characteristics wont have FASD - but that simply isn't true. As babies grow, the facial structures develop in the early part of pregnancy (around days 18-21) and then fill out as the pregnancy progresses. That means that the characteristic facial damage of FASD is only likely to occur if mom is drinking that one particular week. She could skip that week (maybe due to morning sickness she mistakes as a hangover?) and drink every day for the next six months and her baby is very likely not to 'look' alcohol affected.
Kari pointed out this great site that takes a 'normal' baby's facial structures and applies the characteristic FASD indicators to them . This is good for basic knowledge but the truth is that many, many people who have suffered alcohol related pre-birth brain injuries have absolutely no external identifiers. They look may look normal on the outside but in truth they are walking around without the tools and abilities that we expect of 'normal looking' people.