You can only eat 2 6oz serving of fish a week. However like miko_latte said there are so fish to avoid.
My doctor told me that I can eat seafood, just not certain fish such as the ones listed above along with catfish, norther pike, trout, red snapper, lobster,rockfish, farmed Salmon etc.
The ones that are okay are anchovies, clams, farmed catfish, farmed trout(rainbow), herring, mahi mahi, oysters, U.S. farmed tilapia, canned chunk light tuna, crab(dungeness, blue, stone, king). I eat sushi and my doctor said it's perfectly fine. I just prefer not to eat certain seafood like raw squid and raw octopus, not really my taste.
Shrimp is okay to eat as long as it's cooked. No sushi. I think they say to limit your intake of tuna as well.
"The fish that should not be eaten during pregnancy, according to the FDA, include:
Shark
Swordfish
King mackerel
Tilefish"