Foods to Avoid When Pregnant: Fish or No Fish? If you are concerned with which foods to avoid when pregnant, you are probably wondering if you should avoid fish. Though fish has always been considered a healthy source of protein, the levels of contaminants have recently raised concern. Foods to Avoid When Pregnant What contaminants should I be worried about if I am pregnant or nursing? Methylmercury and polychlorinated biphenyls levels are the main contaminants of concern, especially for pregnant and nursing women. According the FDA, trace amounts of methylmercury are not harmful. What are the possible risks associated with excessive consumption of contaminated fish? Eating fish with high levels of methylmercury can cause damage to the unborn baby’s nervous system. Do I need to avoid all fish if I am pregnant? No, but you do need to avoid some fish and you need to limit your fish consumption. Which types of fish should I completely a...