If it's cooked properly then yes.
As Vanessag said, you can eat it, but you have to adhere to certain limits. Fish and seafood are generally discouraged while pregnant, because mercury can cause defects in the baby. Speak to your OB and they will tell you the types of fish that are okay, what amounts are safe and when.
Yes it has omega 3 fatty acids which are essential for baby's brain development
Yes you can, chunk light, 6oz, only once a weeks.