If you trust the place you're having it. I've had scallops, mussles, clams, shrimp, tilapia, tuna.. its all perfectly okay as long as its low in mercury.
I ate scallops with my first pregnancy. Never had food poisening before. I vomited so hard I blew blood vessels in my eyes. Ended up in the hospital hooked to an IV for fluids. I recommend steering clear of scallops.
They're fine...but just be careful because getting food poisoning is worse when pregnant..well at least it feels worse. The main thing to stay away from is the high mercury levels in some fish. They're usually a white fish, although halibut is okay. I mainly stayed away from shrimp because it is so easy to eat bad shrimp.