We've all been advised to eat more seafood. By most accounts, fish is a great choice. It's a low-fat source of protein with promises of improving your heart and health.
However, while some say seafood can help a baby's brain development in the womb, pregnant mothers need to be cautious.
According to Consumer Reports and other researchers, some seafood contains high levels of a form of mercury called methylmercury.
"Mercury can damage the brain and it can damage the nervous system, especially when that exposure occurs in the womb," said Dr. Michael Crupain with Consumer Reports.
New government guidelines encourage women who are pregnant, breastfeeding, or trying to become pregnant to eat between 8 and 12 ounces of fish per week. They even suggest a minimum quota for young children.
But Consumer Reports says pregnant women and children should avoid fish like tuna that are high in mercury. Consumer Reports' food-safety experts say tuna accounts for 40 percent of our mercury exposure, most of that from canned tuna.
"To be safe, Consumer Reports recommends that pregnant women not eat any tuna at all," Crupain said. "Children and anyone who eats a lot of fish should really limit the amount of tuna they eat."
Other fish with high mercury levels are swordfish, shark, king mackerel and tilefish from the Gulf of Mexico.
So what are alternatives for people who want more fish in their diet? Consumer Reports recommends fish like wild Alaskan salmon, shrimp, sardines, tilapia, scallops, oysters and squid.