What not to eat
While most seafood is fine to eat when pregnant, there are some options that should be avoided.
Shark, swordfish, marlin
Don't eat shark, swordfish and marlin, as they contain mercury and other pollutants that can harm your baby's developing nervous system. You should generally avoid having more than two portions of oily fish per week, e.g. salmon, trout, mackerel and herring, because they can contain pollutants such as dioxins and PCBs (polychlorinated biphenyls).
Limit your tuna
Limit the amount of tuna you eat to no more than two medium-sized tuna steaks (weighing about 140g when cooked, or 170g raw) or four medium-size cans of tuna per week (with a drained weight of about 140g per can). Fresh tuna is an oil-rich fish, so if you eat two fresh tuna steaks in one week, you shouldn't eat any other oil-rich fish that week.
During the canning process, the oil-rich content is lost and therefore, tinned tuna doesn't count as oily fish, so you can eat this as well as your two portions of oil-rich fish. But remember not to eat more than four medium-sized cans of tinned tuna per week when you're pregnant or trying to get pregnant.
It's best to avoid raw shellfish (including mussels, lobster, crab, prawns, scallops and clams) when you're pregnant.
Eat your shellfish cooked rather than raw, as the latter can contain harmful bacteria and viruses that can cause food poisoning. Cold pre-cooked prawns are fine though.
If you're unsure about any foods during pregnancy, it's best to check with your doctor.