Eating for two doesn't mean you need to double your calories (you need only an additional 300 calories per day in the second and third trimesters), but you'll definitely want to double your efforts to avoid potentially harmful foods for you and your baby. "Everything you eat and drink you share with your baby, so it makes sense to be extra careful about the foods and drinks you choose during this time," says Bridget Swinney, M.S., R.D., author of Eating Expectantly: A Practical and Tasty Guide to Prenatal Nutrition (Meadowbrook, 1996).

Here's a rundown of certain eats you should stay away from if you're pregnant:

• LARGE FISH
  Shark, swordfish, tilefish, and king mackerel all contain dangerously high levels of methyl mercury, a poison found in fresh and salt waters thanks to industrial pollution. At high levels, mercury can cause damage to the nervous system -- especially to children and unborn babies. Low amounts can also affect the central nervous system, creating things like learning deficits. Since mercury builds up in the body, it's also wise to stay away from these fish if you're planning to become pregnant or are nursing.
  
  Depending on where you live, there may be other types of fish and seafood you'll want to avoid. For a listing by state, visit the Environmental Protection Agency's fish consumption advisory Web page at www.epa.gov/ost/fish. You can also check out "A Woman's Guide to Eating Fish and Seafood," at www.state.nj.us/dep/dsr/womans-guide.htm.
  
  
• IMPORTED SOFT CHEESES
  These cheeses can contain a bacteria called Listeria which can cause miscarriage. Types to avoid include: brie, camembert, roquefort, feta, and gorgonzola, as well as Mexican-style cheese like queso blanco and queso fresco. Soft non-imported cheeses made with pasteurized milk are safe to eat.
  
  
• DELI FARE
  Cold-cuts and cold salads (like tuna and egg) from a deli can also be contaminated with listeria. Swinney advises reheating meats in a microwave to steaming to help kill any potential bacteria, or skipping them altogether.
  
  
• UNDERCOOKED EGGS
  Raw or undercooked eggs (such as poached, sunnyside up, and over-easy) don't reach high enough temperatures to kill off the harmful salmonella bacteria which can be found in egg yolk. A good rule of thumb is not to eat anything with a runny yolk. Alternatively, use egg substitutes, which are pasteurized. Also beware of souffles since they contain undercooked eggs, and traditional Caesar salad dressing made with raw eggs.
  
  
• RAW OR UNDERCOOKED BEEF
  To prevent the risk of E. coli bacteria poisoning or toxoplasmosis, which is harmful to a fetus, make sure meat reaches a temperature of 160 degrees. If you're ordering a burger out, ask for it be cooked well-done and check that there's no pink once it arrives; steaks are fine cooked to medium well (which means they may be a little pink in the center.)
  
  
• HERBAL TEAS
  "We just don't know enough about the effects of herbs during pregnancy, so it makes sense to play it safe and stick with decaf black tea or flavored teas," says Swinney.