The EPA safety limit on mercury in fish may not sufficiently protect pregnant women in the United States. This has led to a recommendation that fish-eating women get tested for mercury before considering getting pregnant.
There is so much more mercury in fish compared to other foods that it can be used as a biomarker for fish consumption: see Hair Testing for Mercury. How much mercury exposure is there from fish, as compared to amalgam fillings and vaccinations? See Amalgam Fillings vs. Canned Tuna, and Mercury in Vaccinations vs. Tuna. Fish aren’t the only source of toxic heavy metals, though. Mercury has been found in both high fructose corn syrup-containing products (see Mercury in Corn Syrup?), and Ayervedic dietary supplements (Get the Lead Out). I also have videos on Aluminum in Vaccines vs. Food, and Arsenic in Chicken.