story
No, we don't. We know that a lot of alcohol poses some risk to some foetuses. We don't know that X drinks a week poses any risk to all foetuses. Maybe it's just harmful to foetuses who are compromised in some way? Maybe it's just harmful to foetuses with a genetic disposition to harm? Maybe it's not harmful at all? We don't know.
> I don't understand the problem with communicating the risk; there are plenty of links in this thread to sources that give information about it, so the information that alcohol poses some risk to a developing fetus is out there.
Some research is just poor quality. Let's ignore that for the moment, and assume that all research is good quality. Lots of popular media is hopeless at reporting science. See the links I posted earlier - that website has many examples of research that's reported with hyperbole, or reports that make mistakes with the statistics, or reports that ignore the research abstract and come up with their own pseudo-abstract which doesn't match the research at all.
And then people have different opinions. See, for example, the discussion around "controlled crying". Controlled crying practices exist on a spectrum ("Just let the baby cry it out" on one end, to over-protective helicopter parenting on the other) and we have a pretty good idea that over-protection is bad, and we have a pretty good idea that the extreme end of crying are both harmful. Yet there's a flood of information from both of these extreme ends. Parents will find it hard to find this information.
Let's not forget that parents tend to be sleep deprived and thus cognitively impaired too.