Even if you've always had a stomach of iron, pregnancy weakens your immune system and makes you more vulnerable to food-borne illnesses that could make you sick and harm your baby. So it's important to avoid certain foods during pregnancy even on special occasions.

"The risks are real, and need to be taken very seriously," says David Acheson, director and chief medical officer of the Center for Food Safety and Applied Nutrition at the U.S. Food and Drug Administration (FDA).