Even if you've always had an iron stomach, 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 learn which foods to avoid during pregnancy – even on special occasions.

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

Dangerous bacteria and parasites like listeria, toxoplasma, salmonella, staphylococcus aureus, and E. coli can lurk in improperly prepared, cooked, and stored foods. And listeria and toxoplasma can cross your placenta and affect your baby even if you never feel symptoms of the illness yourself.

You may have always licked cookie dough off a spoon, enjoyed Caesar salads with raw egg in the dressing, or ordered your burgers medium rare, but pregnancy is a time to err on the side of food safety, experts say.

Here are some tips to get you through summer barbecues, holiday buffets, and other festive occasions without feeling deprived – or getting sick.

Valentine's Day

Chocolates: If your valentine brings you a box of chocolates, feel free to dive right in. But to be on the safe side, don't eat candies filled with alcoholic liqueurs like Grand Marnier or amaretto.

Memorial Day, Fourth of July, and Labor Day

Prepared foods: Prepared salads from the deli (especially those containing protein, like egg, chicken, ham, and seafood) can be contaminated with listeria if they aren't prepared and handled properly. This includes homemade and store-bought salads as well as sandwiches made from these salads.

Ready-to-eat salads that aren't reheated can pose a risk to pregnant women, so you may want to avoid them altogether. If you do choose to eat them, discard any leftovers within four days after preparation.

Also stay away from salads (and other food) left unrefrigerated or unheated. For example, if you arrive at a party and there's a potato salad that's not on ice or meat that isn't on a hot plate, don't eat it unless you know for sure that it's been out for less than two hours (one hour for refrigerated foods if the temperature outside is higher than 90 degrees).

Prepared salads from the deli (especially those containing protein, like egg, chicken, ham, and seafood) can be contaminated with listeria if they aren't prepared and handled properly. This includes homemade and store-bought salads as well as sandwiches made from these salads. Ready-to-eat salads that aren't reheated can pose a risk to pregnant women, so you may want to avoid them altogether. If you do choose to eat them, discard any leftovers within four days after preparation. Also stay away from salads (and other food) left unrefrigerated or unheated. For example, if you arrive at a party and there's a potato salad that's not on ice or meat that isn't on a hot plate, don't eat it unless you know for sure that it's been out for less than two hours (one hour for refrigerated foods if the temperature outside is higher than 90 degrees). Hot dogs and lunch meat: Hot dogs are generally high in nitrates, fat, and sodium. But it's safe to enjoy one now and then, provided it's fresh off the grill or has otherwise been cooked until steaming (165 degrees Fahrenheit) to kill bacteria that may be present. Lunch and deli meats also need to be reheated until they're steaming.

Also be careful when handling packages of hot dogs and lunch meat. Don't let the juice from the packaging come in contact with foods that won't be cooked, and wash your hands thoroughly after handling it.

Hot dogs are generally high in nitrates, fat, and sodium. But it's safe to enjoy one now and then, provided it's fresh off the grill or has otherwise been cooked until steaming (165 degrees Fahrenheit) to kill bacteria that may be present. Lunch and deli meats also need to be reheated until they're steaming. Also be careful when handling packages of hot dogs and lunch meat. Don't let the juice from the packaging come in contact with foods that won't be cooked, and wash your hands thoroughly after handling it. Burgers and other grilled meat or fish: If you're offered a burger or other grilled or barbecued meat, chicken, pork, or fish, make sure it's well done and not pink in any areas. Undercooked meat can harbor E. coli, salmonella, and toxoplasma bacteria.

Ground beef, veal, lamb, and pork should be cooked to at least 160 degrees F, and all poultry to 165 degrees F. Pork roasts and chops need to reach 145 degrees F, and fish 145 degrees F. Use a food thermometer to test the temperature because the color of the food isn't always a good indication of how well it's done.

Note: Because of concerns about mercury in fish, the FDA recommends limiting yourself to 12 ounces (about two servings) of fish a week, and avoiding some kinds of fish altogether. For more information, see our article on eating fish during pregnancy.

Ice cream: Don't eat homemade ice cream made with raw eggs, which can contain salmonella. (Cooking kills the bacteria but freezing doesn't.)

Don't eat homemade ice cream made with raw eggs, which can contain salmonella. (Cooking kills the bacteria but freezing doesn't.) Ice: Use clean ice for your drinks, not the ice that's keeping the meat cold or that others have stuck their hands into. Bacteria can thrive in a cooler full of ice.

Use clean ice for your drinks, not the ice that's keeping the meat cold or that others have stuck their hands into. Bacteria can thrive in a cooler full of ice. Raw sprouts: Don't garnish your burger or salad with alfalfa or other raw sprouts. They can contain E. coli or salmonella bacteria. For the same reason, make sure raw vegetables – lettuce and cabbage in particular – have been washed.

Halloween

Raw cookie dough or cake batter: If you're making Halloween cookies or cupcakes, resist the temptation to sample the batter. The raw eggs in cookie dough and cake batter could contain salmonella or other bacteria that can make you sick. Stick with store-bought goodies or bake your treats without tasting the uncooked batter.

Thanksgiving

On turkey day (as on every other day), it's important to be vigilant against germs and bacteria in the kitchen. Wash your hands frequently when preparing meals, and be careful to clean any surface that has come in contact with raw meat or eggs before using it for other foods. Use separate cutting boards for poultry and produce, and keep uncooked poultry and meat chilled in the refrigerator and separate from other food items.

Don't leave leftovers out for longer than two hours, and store them in shallow containers so they'll cool quickly. Set your refrigerator between 35 and 40 degrees F and your freezer at or below zero to keep cold foods from going bad.

Turkey and stuffing: Cook turkey until it reaches an internal temperature of 180 degrees F. (Use a meat thermometer to check it.) If you're preparing stuffing (also known as dressing), cook it in a separate baking dish to 165 degrees F. The inside of a stuffed turkey doesn't get hot enough to kill harmful bacteria.

Cook turkey until it reaches an internal temperature of 180 degrees F. (Use a meat thermometer to check it.) If you're preparing stuffing (also known as dressing), cook it in a separate baking dish to 165 degrees F. The inside of a stuffed turkey doesn't get hot enough to kill harmful bacteria. Unpasteurized cider and juice: Make sure apple cider (whether hot or cold) is pasteurized before you drink it. Unpasteurized juices, including cider, are unsafe to drink during pregnancy because they can contain bacteria, including E. coli. Almost all juice sold is pasteurized, and unpasteurized juice sold in containers must be labeled as such.

Note: Year round, you'll want to avoid juice served at juice bars, especially if it's freshly squeezed because there's a good chance it's not pasteurized.

Smoked meats and meat spreads: If you're serving meat spreads (like pâté), or smoked fish (such as smoked salmon or trout), make sure they're canned, not from the refrigerated section of the grocery store. Refrigerated meat spreads and smoked meats, fish, and shellfish can contain listeria, so it's only safe to eat them if they're heated until steaming or part of a dish that has been cooked.

Winter holidays

Unpasteurized soft cheeses: Stay away from soft cheeses made with unpasteurized milk. Unpasteurized or "raw milk" cheeses may contain listeria, which is killed during the pasteurization process.

The FDA recommends checking the label of any soft cheese to make sure it says "made with pasteurized milk." If you can't check the label – if you're at a party, for example – avoid blue cheese and soft cheeses (including Brie, Camembert, goat cheese, feta, and Roquefort) and Mexican-style cheeses (like queso fresco, queso blanco, and panela).

If you're not sure which cheeses are safe, stick with hard cheeses, like cheddar and Swiss, and semi-soft cheeses, like Monterey jack and mozzarella. Cream cheese and pasteurized processed cheeses like American are also safe.

Stay away from soft cheeses made with unpasteurized milk. Unpasteurized or "raw milk" cheeses may contain listeria, which is killed during the pasteurization process. The FDA recommends checking the label of any soft cheese to make sure it says "made with pasteurized milk." If you can't check the label – if you're at a party, for example – avoid blue cheese and soft cheeses (including Brie, Camembert, goat cheese, feta, and Roquefort) and Mexican-style cheeses (like queso fresco, queso blanco, and panela). If you're not sure which cheeses are safe, stick with hard cheeses, like cheddar and Swiss, and semi-soft cheeses, like Monterey jack and mozzarella. Cream cheese and pasteurized processed cheeses like American are also safe. Sushi: Avoid sushi trays with raw fish, which may contain parasites and bacteria. If you're a sushi fan, opt instead for a California roll made with avocado and cooked crab. Although raw fish poses little direct risk to your baby, if you get ill from sushi you'll probably suffer from vomiting and dehydration, which can affect your unborn baby.

Avoid sushi trays with raw fish, which may contain parasites and bacteria. If you're a sushi fan, opt instead for a California roll made with avocado and cooked crab. Although raw fish poses little direct risk to your baby, if you get ill from sushi you'll probably suffer from vomiting and dehydration, which can affect your unborn baby. Carving stations: Make sure the meat is cooked well-done and is still steaming hot. Unless you're sure they're well cooked, avoid sauces like béarnaise, hollandaise, and aioli, which can contain uncooked eggs.

Make sure the meat is cooked well-done and is still steaming hot. Unless you're sure they're well cooked, avoid sauces like béarnaise, hollandaise, and aioli, which can contain uncooked eggs. Eggnog: Homemade eggnog is generally off-limits because it's usually made with raw, unpasteurized eggs – and alcohol. But you can make a virgin, pregnancy-safe version at home with pasteurized eggs, a pasteurized egg product, or an egg alternative. Or try store-bought eggnog (just check the label to make sure the eggs are pasteurized).

You might also consider "soy nog," which doesn't contain eggs or any other dairy products. You can find it during the winter holidays in most large grocery stores and in natural food stores.

You'll also want to avoid desserts that may contain raw or undercooked eggs, like some custards, mousse, and homemade ice cream.

Homemade eggnog is generally off-limits because it's usually made with raw, unpasteurized eggs – and alcohol. But you can make a virgin, pregnancy-safe version at home with pasteurized eggs, a pasteurized egg product, or an egg alternative. Or try store-bought eggnog (just check the label to make sure the eggs are pasteurized). You might also consider "soy nog," which doesn't contain eggs or any other dairy products. You can find it during the winter holidays in most large grocery stores and in natural food stores. You'll also want to avoid desserts that may contain raw or undercooked eggs, like some custards, mousse, and homemade ice cream. Fruitcake and other alcoholic food items: Fruitcake and other desserts that use alcohol as an ingredient are generally okay, because most of the alcohol burns off during cooking. If the fruitcake has been soaked in rum or other liquor after being baked, however, little of the alcohol will have evaporated and you should probably not eat it.

New Year's Eve

Raw oysters and other shellfish: Stay away from uncooked shellfish, including oysters, clams, mussels, and scallops. Cook shellfish until the shell opens to ensure that any bacteria or parasites have been killed. Discard any shellfish that doesn't open during cooking because this means that the shellfish was dead before cooking and may have been sick.

Stay away from uncooked shellfish, including oysters, clams, mussels, and scallops. Cook shellfish until the shell opens to ensure that any bacteria or parasites have been killed. Discard any shellfish that doesn't open during cooking because this means that the shellfish was dead before cooking and may have been sick. Champagne and other alcoholic beverages: It's best to avoid alcohol altogether when you're pregnant. Even one glass of wine or one beer can affect your baby's growth, according to a 2015 report from the American Academy of Pediatrics. Consider celebrating instead with a glass of sparkling apple or grape cider or soda, or try a festive non-alcoholic cocktail.

More safe-eating tips