The hype has all been about limiting or avoiding seafood when you're pregnant. There's the possibility that some seafood might have a high mercury content. The FDA issued this warning back in March of 2004:

You can protect your unborn child by not eating these large fish that can contain high levels of methylmercury:

Shark
Swordfish
King mackerel
Tilefish

As long as you select a variety of other kinds of fish while you are pregnant or may become pregnant, you can safely enjoy eating them as part of a healthful diet. You can safely eat 12 ounces per week of cooked fish. A typical serving size of fish is from 3 to 6 ounces.

However, Ivanhoe Medical Breakthroughs now reports that, for a smarter child, eating seafood during pregnancy is the way to go. Researchers from the U.S. National Institutes of Health and Bristol University in England studied roughly 12,000 pregnant women who completed a food questionnaire assessing their seafood consumption at 32 weeks gestation.

Results of the study reveal women who ate less than 340 grams of fish a week (less than three portions) were more likely to have children in the lowest quartile of verbal IQ, when compared to mothers who ate more than 340 grams per week. Low seafood consumption was also associated with a higher risk of suboptimal outcomes for prosocial behavior, fine motor, communication and social development scores. Researchers found the lower the seafood consumption, the higher the risk of a suboptimal outcome.

So, it's left up to you. Fish contain beneficial Omega 3 fatty acids that help the fetus develop better brains. Mercury, on the other hand, can cause all sorts of problems, including damaging the central nervous system. In her Food Blog, Barbara Fisher tells us:

It -would- be all kinds of great if it wasn't for the fact that thanks to coal burning power plants and pollution from heavy industry, our oceans and waterways are all contaminated with a compound called methyl mercury. Methyl mercury makes its way into the food chain, and eventually into us insidiously by being consumed by small critters such as filter feeders or plankton, which in turn get eaten by consecutively larger fish, until those big, tasty fatty fish full of their wonderful omega 3's get caught and eaten by us, humans, the critters at the top of the food chain.