According to the U.S. Food and Drug Administration (FDA), pregnant women can eat up to 12 ounces a week of fish and shellfish that have low levels of methylmercury (salmon, canned light tuna, and shrimp). Albacore ("white") tuna has more methylmercury than canned light tuna; pregnant women should consume 6 ounces or less in a week. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.