Fish is good for you and your baby, but make smart choices about the fish you eat. Swordfish, tilefish, king mackerel, and shark contain high levels of methylmercury. This metal can be harmful to your baby. You can safely eat up to 12 ounces of seafood a week, so choose fish that are low in mercury: catfish, salmon, cod, and canned light tuna. If you like albacore (white) tuna, limit yourself to 6 ounces per week. Check with your doctor before taking fish oil or any other supplements while pregnant.