Raw, fresh seafood is risky to eat because it can contain parasites such as tapeworms. If tapeworms grow large enough they will rob your body of the nutrients required for the growing baby. The process of freezing and cooking kills these parasites. It is for this reason, that many Japanese sushi restaurants use frozen rather than fresh fish. Some restaurants lightly sear fresh fish on the outside and then serve it rare. You are safer if you order or fish well cooked.
Shellfish, especially oysters should be avoided unless they have been thoroughly cooked and are served as part of a hot meal. These types of seafood served raw, could be contaminated with harmful bacteria and viruses that cause food poisoning. Pregnancy suppresses the immune system, so pregnant women are particularly susceptible to food poisoning. Proper cooking makes these shellfish safe to eat, bacteria and viruses are usually killed by the heat used in the cooking process.
If you cook seafood at home, you should cook the seafood to an internal temperature of 63 degrees Celsius or 145 degrees Fahrenheit for at least 15 seconds. You may find the guidelines below helpful in checking seafood if you don't have a thermometer.
• When cooking fish, slip the point of a sharp knife into the flesh of the seafood and slightly pull aside. The edges of the flesh should be opaque and the centre slightly translucent, with flakes just beginning to separate. Allow the fish stand three to four minutes to finish cooking.
• Prawns and lobster will turn red when fully cooked and the flesh becomes pearly opaque. Scallops are firm and appear milky white or opaque when cooked.
• Watch for the point when the shells open up for clams, mussels and oysters. This indicates that they're done. Throw out those that remain closed after cooking.
• Rotate the dish several times to ensure even cooking when microwaving seafood. Check the seafood in several spots with a thermometer after allowing the dish to stand a few minutes, to see if it has reached the proper temperature.
Whether it is raw or cooked, contamination with environmental pollutants such as PCBs (polychlorinated biphenyls) and dioxins is a concern with all seafood. Oily fish tends to have more of these pollutants than white fish, so it is recommended that pregnant women avoid eating too much. Limit your fish intake to two portions a week. You do need a little oily fish, because it contains the omega-3 fatty acids and other vitamins and nutrients that are good for you and the developing baby. Avoid eating shark, swordfish and marlin because they have high levels of mercury, which could harm the baby's developing nervous system. Limit the amount of tuna you eat as it contains relatively high levels of mercury.