During early pregnancy, your immune system dials down to protect the developing embryo, which makes you significantly more vulnerable to foodborne infections. At the same time, the first trimester is when your baby’s major organs, brain, and spinal cord are forming, so certain substances can interfere with that process in ways they wouldn’t later. The foods to avoid fall into two categories: those that carry a higher risk of dangerous infections and those that contain compounds that can directly harm fetal development.
High-Mercury Fish
Mercury accumulates in large, long-lived predatory fish and crosses the placenta easily. In a developing baby, it can damage the brain and nervous system. The FDA lists seven fish to avoid entirely during pregnancy: king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish, and bigeye tuna.
That doesn’t mean you should skip seafood altogether. Fish is one of the best sources of omega-3 fatty acids, which support your baby’s brain development. Stick to two or three servings per week from lower-mercury options like salmon, shrimp, cod, tilapia, sardines, catfish, pollock, and canned light tuna (skipjack). Albacore (white) tuna has more mercury than light tuna, so limit it to one serving per week.
Raw and Undercooked Meat
Undercooked beef, pork, and poultry can harbor parasites that cause toxoplasmosis and bacteria like Salmonella. Toxoplasmosis is particularly dangerous in the first trimester because the parasite can cross the placenta and damage the baby’s brain and eyes. The safe internal temperatures to remember: whole cuts of beef, pork, veal, and lamb need to reach 145°F (63°C) with a three-minute rest. Ground meat needs to hit 160°F (71°C). All poultry, whether whole or ground, needs to reach 165°F (74°C). A meat thermometer is the only reliable way to check. Color alone doesn’t tell you enough.
Deli Meats and Prepared Cold Cuts
Sliced deli meats, hot dogs, and pâtés are a well-documented source of Listeria, a bacterium that pregnant women are about 10 times more likely to contract than other healthy adults. Listeria can cause miscarriage, stillbirth, premature delivery, and serious infections in newborns including meningitis. Unlike most bacteria, Listeria grows at refrigerator temperatures, so simply keeping deli meat cold isn’t enough.
If you want deli meat during pregnancy, heat it to 165°F or until it’s visibly steaming before eating it. That temperature kills the bacteria. Pre-packaged lunch meats carry the same risk as freshly sliced ones from the deli counter.
Soft Cheeses and Unpasteurized Dairy
Listeria is also the concern here. The FDA advises avoiding any cheese made from unpasteurized (raw) milk during pregnancy. Queso fresco, queso blanco, and requesón deserve extra caution because they can harbor Listeria even when made from pasteurized milk, due to how they’re processed. Soft-ripened cheeses like brie, camembert, and blue-veined varieties are safe only if the label confirms they’re made from pasteurized milk. Hard cheeses like cheddar and parmesan, and pasteurized cottage cheese and cream cheese, are fine.
Raw or Runny Eggs
Raw eggs can carry Salmonella, which causes severe vomiting and diarrhea that can lead to dehydration and, in rare cases, uterine contractions. The obvious sources are easy to spot: sunny-side-up eggs, soft-boiled eggs, raw cookie dough. The less obvious ones catch people off guard. Homemade Caesar dressing, hollandaise sauce, homemade mayonnaise, mousse, tiramisu, and some homemade ice creams all contain raw or lightly cooked eggs.
You don’t have to give up these foods entirely. Pasteurized eggs have been heat-treated to kill Salmonella and work as a direct substitute in any recipe that calls for raw eggs. Pasteurized shell eggs will say so on the carton. Store-bought versions of Caesar dressing and mayonnaise almost always use pasteurized eggs and are generally safe.
Raw Sprouts
Alfalfa, clover, radish, and mung bean sprouts grow in warm, humid conditions that are ideal for Salmonella, Listeria, and E. coli. The bacteria can get inside the seed itself before the sprout even grows, so washing doesn’t help. The CDC specifically advises pregnant women to avoid all raw sprouts. Cooking sprouts thoroughly kills the bacteria, so stir-fried bean sprouts in a hot dish are fine.
Unpasteurized Juice and Cider
Fresh-squeezed juice from a farmers’ market or juice bar, and unpasteurized apple cider, have been linked to outbreaks of E. coli and other harmful bacteria. Packaged juice sold in the refrigerated section that hasn’t been pasteurized is required to carry a warning label, so check before buying. Shelf-stable juice boxes and bottles have been pasteurized. If you only have access to unpasteurized juice or cider, bringing it to a rolling boil for at least one minute makes it safe.
Liver and High-Dose Vitamin A
This one surprises many people. Liver is packed with nutrients, but it contains extremely high concentrations of preformed vitamin A (retinol). A single serving of beef liver can deliver well over 20,000 IU of vitamin A. The World Health Organization recommends pregnant women stay below 10,000 IU per day, especially during the first 60 days when the embryo’s most critical development is happening.
Excess retinol interferes with genes that guide fetal development. Studies have linked daily intake above 10,000 IU to nervous system abnormalities, heart defects, and an increased risk of miscarriage. Intake above 25,000 IU per day has been associated with urinary tract malformations. This applies to preformed vitamin A from animal sources and supplements, not to beta-carotene from vegetables like carrots and sweet potatoes, which your body converts to vitamin A only as needed. The practical takeaway: skip liver and liver pâté in the first trimester, and check your prenatal vitamin to make sure it contains beta-carotene rather than retinol, or that the retinol dose stays well under 10,000 IU.
Alcohol
There is no known safe amount of alcohol during pregnancy. The CDC is unequivocal on this point: no amount, no type (wine and beer included), and no trimester is considered safe. Alcohol crosses the placenta freely, and the first trimester is when the brain and spinal cord are forming. Fetal alcohol spectrum disorders can result from exposure at any point, but early exposure carries particular risk because the embryo’s cells are dividing and differentiating so rapidly.
Caffeine
You don’t need to cut caffeine entirely, but you should keep it moderate. The American College of Obstetricians and Gynecologists considers less than 200 mg per day unlikely to be a major contributor to miscarriage or preterm birth. That’s roughly one 12-ounce cup of brewed coffee. Keep in mind that caffeine adds up from multiple sources: tea, soda, chocolate, and energy drinks all contribute. A large coffee-shop drink can easily exceed 200 mg in a single cup, so check serving sizes.
A Practical Note on Hidden Ingredients
Many of these risky foods show up in dishes where you wouldn’t expect them. Restaurant sauces may contain raw egg. A charcuterie board at a party will have cured, unheated deli meats and soft cheeses. Smoothie bars may use unpasteurized juice as a base. Asking about ingredients when eating out and reading labels when shopping are the two habits that make the biggest practical difference. The list of what you can safely eat is far longer than the list of what to avoid.