Women who follow government guidelines and eat no more than three portions of fish a week during pregnancy increase the risk of their children developing poor verbal and social skills, a new study by the National Institutes of Health suggests, because omega-3 fatty acids in fish appear to promote brain growth during fetal development.

In 2004 the US Environmental Protection Agency and FDA jointly advised pregnant and nursing women against eating more than 340 g of seafood because of concerns about levels of toxic mercury in fish.