Here's something I found doing a quick search:
I love sushi. Should I avoid it while pregnant?
Written for BabyCentre UK
It's safe to eat sushi when you're pregnant as long as the raw fish used to make it has been frozen beforehand. This is because occasionally fish contains parasites such as tapeworms, which could make you unwell if they are still alive when you eat the fish. Freezing kills the parasites and makes raw fish safe to eat.
Most of the sushi sold in supermarkets is bought in ready made, not made at the shop. This type of sushi should be safe to eat, because if a shop or restaurant buys in ready-made sushi, the raw fish used to make it must have been frozen at minus 20 degrees C for at least 24 hours.
But if a shop or restaurant makes its own sushi, the fish might not have been frozen beforehand. If you're concerned, ask the staff if they freeze fish before serving it raw.
Sushi which uses cooked fish, such as steamed crab and cooked eel, is fine to eat while you're pregnant.
If you make your own sushi at home using raw fish, freeze the fish for at least 24 hours before using it.
Sushi is safe to eat when breastfeeding.
Reviewed May 2008