Source : http://www.eatwell.gov.uk/asksam/healthydiet/fiasandshellfishq/#A219871I've heard that pregnant and breastfeeding women should avoid some types of fish. Why is this?
You can eat most types of fish when you're pregnant or breastfeeding. Eating fish is good for your health and the development of your baby. But you should avoid some types of fish and limit the amount you eat of some other types.
When you're pregnant or planning to get pregnant, you shouldn't eat shark, swordfish or marlin. You should also limit the amount of tuna you eat to no more than two tuna steaks (weighing about 140g when cooked, or 170g raw) or four medium-size cans of tuna a week (with a drained weight of about 140g per can).
This is because these fish contain more mercury than other types of fish. The amount of mercury we get from food isn't harmful for most people, but if you take in high levels of mercury when you're pregnant this could affect your baby's developing nervous system. When you're breastfeeding you don't need to avoid shark, swordfish or marlin, or limit the amount of tinned tuna you eat.
When you're pregnant, you should generally avoid having more than two portions of oily fish a week, such as salmon, trout, mackerel and herring, because it can contain pollutants such as dioxins and PCBs (polychlorinated biphenyls).
Remember that fresh tuna is an oily fish, so if you eat two fresh tuna steaks in one week, you shouldn't eat any other oily fish that week. Tinned tuna doesn't count as oily fish, so you can eat this on top of the maximum of two portions of oily fish (as long as it's not fresh tuna or swordfish). But remember not to eat more than four medium-sized cans of tinned tuna a week when you're pregnant or trying to get pregnant.
There is no need to limit the amount of white fish you eat when you're pregnant or breastfeeding, apart from shark and marlin.