Fish

There are some types of fish you should avoid completely, such as shark, marlin and swordfish. These contain high levels of mercury that can damage your baby's developing nervous system.

Also, don't eat more than two portions of oily fish, such as fresh tuna, salmon, mackerel, sardines and trout a week. Limit tuna to no more than two tuna steaks or four medium-sized cans of tuna per week.

It's safe to eat smoked fish (such as smoked salmon) while pregnant.

Shellfish

Only eat cooked shellfish as raw shellfish can contain harmful bacteria and viruses that cause food poisoning.

Sushi

It's fine to eat sushi and other dishes made with raw fish when you're pregnant, as long as the fish has been frozen first. This is because freezing kills the small parasites that can be found in raw fish.

Ready-made sushi sold in shops or restaurants should be fine to eat, because the fish used to make it will have been frozen at minus 20°C for at least 24 hours. If you're in any doubt, avoid eating sushi with raw seafood such as tuna, and stick to fully cooked or vegetarian varieties instead.

If you make your own sushi at home, freeze the fish for at least 24 hours first (although smoked salmon doesn't need to be frozen, because smoking acts in the same way as freezing).