Caviar is another seafood product that should be avoided during pregnancy. Unless the caviar is pasteurized, the risk is listeria. Listeria can cause miscarriage, stillbirth, or premature delivery. The American College of Obstetricians and Gynecologists advises against eating caviar during pregnancy because of the risk of contamination by bacteria such as streptococcus, which can lead to inflammation of the heart valves and other serious health problems for the mother and her baby. Fish with high levels of mercury should also be avoided during pregnancy. Fish with high levels of mercury include king mackerel, swordfish, marlin, shark, tilefish, and amberjack. If you eat fish, try to avoid those with high levels of mercury at least until you have discussed potential risks with your doctor. Fish is one of the best sources of protein for women who are pregnant or trying to get pregnant. But like any other food, it can be contaminated with chemicals from pesticides to heavy metals. Too much of certain pollutants in fish has been linked to birth defects and other problems for the mother and child. Fish contains omega-3 fats that are good for brain development and control of blood pressure.