Pregnancy: Eating Healthy for 2 (cont.)

However, Ashton reminds us that high levels of mercury contamination could turn eating some seafood into a serious risk with the potential to harm the nervous system of your developing baby.

As such, in 2004 the FDA and the Environmental Protection Agency warned pregnant women, those looking to get pregnant, nursing mothers, and children, to avoid all seafood high in mercury. This includes larger fish that live longer such as shark, swordfish, King mackerel, and tilefish.

According to the March of Dimes, you can safely consume up to 12 ounces (two average meals) per week of fish that is lower in mercury. This includes shrimp, canned light tuna, salmon, pollack, and catfish. The FDA, however, suggests limiting albacore (white) tuna, and tuna steak to 6 ounces per week. These two contain more mercury than canned light tuna.

In addition, Heller cautions against eating any kind of raw fish during pregnancy -- regardless of the type, since it can "harbor bacteria and parasites that are very dangerous during pregnancy," she tells WebMD.

No. 4: Excessive Caffeine

In moderate amounts caffeine is not likely to be harmful. But experts say there is some concern that in greater amounts beverages or medicines containing high levels of caffeine could pose a problem.

"There isn't anything definitive on caffeine but there is some suggestion it may increase the risk of miscarriage and low birth weight -- plus, it's a mild stimulant and a diuretic, both of which are not ideal during pregnancy," says Aston.

If you can avoid it, she says, that's good. If you can't Ashton says try to limit consumption to about 300 mg daily, the amount found in around 3 cups of coffee.

The March of Dimes also reminds us that sodas (such as Coke, Pepsi, and Mountain Dew) as well as certain medications (such as Anacin) also contain caffeine, so be sure to count them into your daily tally as well.

No. 5: Unpasteurized Cheeses and Lunch Meats

The problem here is a form of food poisoning known as listeriosis. Caused by a bacterium known as Listeria monocytogenes, it can increase the risk of miscarriage, premature birth, or stillbirth. A newborn baby exposed to Listeria can become seriously ill and die.

This bacteria lurks in foods that are unpasteurized -- particularly soft cheeses such as feta, Brie, Camembert, Roquefort, blue-veined, queso blanco, queso fresco, or Panela. Listeria can also be found in unpasteurized fruit juices, as well as hot dogs or deli meats such as ham, turkey, salami, or bologna.

Heller says that because pasteurization kills this bacterium, any soft cheese made from pasteurized milk is fine to eat.

While most of the time the label will say if, in fact, the product is pasteurized, Heller tells WebMD that "If you're not sure, don't hesitate, just skip it."