This whole issue is incredibly emotive. It makes me very uncomfortable. I'm a scientist (genetics of development and cancer, so I probably have quite a good insight into this.) this is a long post, sorry for that.
What I dislike about this debate is the fact that it feels like the thin end of the wedge in terms of the pregnant woman being public property. Go too far down that road and you end up with a situation like that in parts of the USA, where women are wombs on legs with no rights of their own. Women are generally sensible and just need information.
On the other hand, there is no doubt that a. Alcohol is a teratogen and b. Many more of us than we'd think have complex relationships with alcohol. For that reason alone it's vital that women are given advice based on solid data.
Ok so now the problem with getting that data - firstly, you can't experiment on pregnant women and so you have to rely on retrospective data gathering. Secondly, people do not report alcohol intake accurately. Thirdly, people underestimate intake - one unit is about 80ml of wine.
So of course what we want to know is, "yes I know don't overdo it, but is it ok to have a glass of wine with good now and again?' And the answer to that is, we just don't know. Everyone metabolises ethanol differently. Some people have one or no copies of the alcohol dehydrogenase gene, for example. If you're a regular drinker the liver ramps up enzyme production too, then there's an interplay with body mass, fat stores, blah blah...So we could line up everyone on this thread and give them two big glasses of vino and you'd have some gently snoring on the sofa and some feeling fine. That's one confounding factor. Then there's the fact that the foetus is vulnerable differently at different stages and it's not just a gradient from more vulnerable to less. There are various processes that will be affected more and we honestly don't know when they are. There's also a VAST spectrum of damage known as fasd which is pretty much impossible to tease out from so many other syndromes.
its also worth remembering that the foetal liver is not fully working in the womb. The foetus will excrete ethanol into the amniotic fluid and thus be exposed to it for much longer than the mother. So a couple of units for me is a bath in it for babs.
It's a very, very difficult issue for public health to call on. The truth is that alcohol does cause damage, but the threshold and timing is impossible to call. What's fine for one woman isn't for another.
Personally, I think the latest advice is good. Cut down if you're ttc. If you think you might be knocked up, abstain. Don't drink at all in the first trimester. Drink nothing or very small amounts from then on. And be aware of what a unit is. A 175ml glass of wine is almost two. Half a glass of champers at a wedding at twenty weeks with food and plenty of water is not going to harm your baby. Wine twice a week might.
I also feel very strongly that demonising women does no good. There needs to be real and immediate help for women who have problems with alcohol.
information and free choice - not coercion and damnation!