It is generally believed that eating fish is beneficial for pregnant women and their fetuses. However, in recent years, the United States has listed four types of fish (shark, swordfish, king mackerel, and tilefish) as having excessively high mercury content, making them unsuitable for consumption by pregnant women, women planning to become pregnant, nursing mothers, and young children.
Subsequently, additional seafood with excessive mercury levels was identified, and seven more types were added to the blacklist to protect women and young children from mercury poisoning. These seven types are tuna, Gulf oysters, sea bass, halibut, mahi-mahi, pike, and white croaker. Authorities also recommend that pregnant women should limit their consumption of canned tuna, escolar, cod, and pollock, as these canned fish also contain high levels of mercury, with consumption limited to once a month. U.S. authorities have stated that seafood that is safe for pregnant women to eat includes farmed trout and catfish, shrimp, flounder, Pacific salmon, yellowtail, mid-Atlantic blue crab, and black sea bass.
Research has shown that excessive mercury absorption by the fetus in the womb can affect the development of brain nerves, leading to future learning disabilities and delayed intellectual development.