I didn’t. Personal choice.
The research (and I am a geneticist with a focus on human development) says that:
Alcohol is a teratogen
There’s no safe limit known
Very low level drinking during pregnancy is not associated with adverse outcomes.
Hence the NHS advice, which is cautious but evidence based.
A single one off drink with food, taken slowly is not going to do you any harm. I personally wouldn’t drink regularly or any more than one. People have very different sensitivities to alcohol and I suspect there are a few specific windows during which the foetus is much more vulnerable
The line public health have to tread is a hard one - there is a huge issue with alcohol in the uk. It’s thought a couple of percent of babies are born with alcohol related issues. People tend to use limits as something to target rather than as a limit, and people are terrible at judging units anyway. Then we also have to make sure that women’s autonomy is respected - we can only give advice and offer support, not ban women from doing stuff.
There are a LOT of pregnant women drinking too much - and yet the angst seems to come from women worried about half a shandy. To me that indicates that the women who need help aren’t getting it.
Anyway, if you want half a shandy/lager then that isn’t going to do you much harm. Drink it slowly and with food.