I actually looked into this a little while ago, as unfortunately I am craving sushi too - but not the veggie sort - I really, really, really want a huge plate of raw fish sushi, with ginger, wasabi...the works!
Now, the type of sushi you are craving is actually safe to eat - anything veggie / or cooked is absolutely fine...and according to the NHS website, eating some raw sushi is also ok - as long as the fish has been frozen in transit to the restaurant. So mini sushi packs that you buy in the supermarket would not be safe...but if the restaurant you are going to keeps the sushi frozen for at least 24 hours at minus 20 degrees, this will apparently kill the harmful bacteria.
However...if you cannot have a 100% guarantee that the above has taken place, it is definitely best to avoid it.
I did wonder if a national full of Japanese ladies, suddenly stopped eating Sushi throughout pregnancy and after a little bit of research, it appears that eating raw fish is "considered part of good neonatal nutrition". Of course, maybe they do not indulge whilst out in restaurants and only prepare it at home where they have full control of the fish and preparation - who knows??
I also wondered the same thing about a nation of French ladies too (not wanting to stereotype or cause offence though!) - I wonder if they avoid pate / soft & blue veined cheeses..??
Again, do nations that usually eat alot of cold meats (Germans, Italians etc), change their daily routine and avoid them completely...?
I wonder if it is just the UK that has an abundance of food rules throughout pregnancy...? My mum tells me time and time again that these rules werent around "in her day" and the children of those days grew up without any problems - and I have to admit, I kind of see where she is coming from...but at the same time, I am trying to govern my diet in accordance with these rules, because I do not want to put my unborn little one at any risk!!
Sorry for the biography...lol!!