If you're trying to get pregnant, up your intake of omega-3 amino acids found in flaxseed, fish, and eggs, says Katz, because they have been shown to help with the brain development and visual acuity of your unborn baby.

Also make sure you're getting enough folic acid. Good food sources of folic acid include asparagus, black-eyed peas, kidney beans and orange juice.

Pregnancy increases the risks of food-borne illness, so skip the sushi, raw oysters, and soft cheeses, to name a few. Katz also advises to steer clear of swordfish, unpasteurized milk or soft cheeses (such as brie or Camembert), pate, and raw or undercooked meat and poultry. All are possible sources of bacteria that can harm an unborn child.

It's well known that drinking during pregnancy can cause physical defects, learning disabilities, and emotional problems in children. Many experts suggest giving up alcohol for your entire pregnancy.

Ditto for caffeinated beverages, such as coffee, tea, soft drinks, cocoa, and chocolate, especially early on in your pregnancy. Some studies suggest that drinking more than four cups of coffee a day can lead to miscarriage, low birth weight, and sudden infant death syndrome. Better bets: skim milk, 100 percent fruit juice, or water with a squeeze of lemon.

If you're infertile, studies have shown that taking vitamin C and zinc also can be found in foods, such as whole grains (especially the germ and bran), whole-wheat bread, legumes, nuts, and tofu.

A folic acid supplement before you conceive (400 micrograms a day, up to 800 mcg. while trying to conceive) and early in your pregnancy (600 to 800 mcg.) may be a good bet, since lack of this B vitamin has been linked to neural tube birth defects, such as spina bifida. Dieting during pregnancy is risky for you and your developing baby, as it can leave you short on iron, folic acid, and other important vitamins and minerals.