This is insane! And I say that as a pregnant woman with a very much wanted and long awaited baby!
Also it doesn't tally with my understanding of the evidence for drinking and pregnancy either - my understanding (and I have an Oxbridge science degree) is that (a) we know lots of alcohol in pregnancy = bad as it can lead to foetal alcohol syndrome (b) we don't know what the limit is where small amounts of drinking tip over into risk of FAS therefore (c) we advise pregnant women not to drink at all.
There is no evidence at all that low or moderate alcohol consumption is harmful, but we don't know what the limit is, as it is considered highly unethical to do experiments to understand where the cutoff between low/moderate and harmful lies, so the advice has been to avoid alcohol altogether.
Therefore to make a blanket statement that all women who might have a baby (and those who are just the right age...!) doesn't even make sense based on the evidence, which suggests a significant amount of alcohol is needed to cause harm, probably over an extended period of the pregnancy. The proportion of women who are heavy enough drinkers to cause FAS and don't realise they are pregnant and would even care about WHO advice is tiny, so I don't know what this is supposed to achieve either.