When should you start watching how and what you eat when you are pregnant?

Right away: Obviously, you should eat right and exercise prior to pregnancy. But as soon as you find out you are pregnant, be sure to understand which foods are safe/unsafe. It's best if you can get your nutrition from your food, so having a well balanced diet is key (fruits, vegetables, meat, diary, fat and carbohydrates). A prenatal vitamin is important too. Make sure you get enough Folic Acid too!