The UK's Food Standards Agency (FSA) has advised pregnant and breastfeeding women, and women who intend to become pregnant, to limit their consumption of tuna to no more than two medium-size cans or one fresh tuna steak per week, because of the amount of mercury the fish contains. The FSA said this precautionary advice is to protect against the small risk to the unborn child, and breast-fed babies, from mercury in certain fish. This is because mercury can harm an unborn child's developing nervous system. Pregnant and breastfeeding women are also advised to avoid eating shark, swordfish and marlin.