The first trimester is when your baby’s major organs, brain, and spinal cord are forming, which makes it the most sensitive window for avoiding certain foods, substances, and exposures. Most of what you need to sidestep is straightforward once you know the list. Here’s what actually matters and why.
Foods That Carry the Highest Risk
Pregnancy suppresses parts of your immune system, which makes you significantly more vulnerable to foodborne illness. You’re 10 times more likely to get a Listeria infection than someone who isn’t pregnant, and infections like Listeria, Salmonella, and Toxoplasma can cause miscarriage, stillbirth, or serious harm to a developing baby. The foods to skip aren’t random. They share a common thread: they’re either raw, unpasteurized, or prone to bacterial contamination during storage.
Avoid raw or undercooked meat, poultry, and eggs. That means no runny yolks, no rare steaks, no homemade Caesar dressing, and no raw cookie dough or cake batter (raw flour itself can carry bacteria). Skip sushi, sashimi, ceviche, and raw shellfish entirely.
Deli meats, hot dogs, and cold cuts are a common Listeria source unless you heat them until steaming. The same goes for refrigerated smoked seafood like lox or kippered salmon, unless it’s part of a cooked dish. Premade deli salads (potato salad, tuna salad, chicken salad, egg salad, coleslaw) are also risky because of how they’re stored and handled.
For dairy, avoid anything made with unpasteurized (raw) milk. That includes soft cheeses like queso fresco, brie, camembert, and blue cheese when made from raw milk. Fresh, soft cheeses like queso fresco and queso blanco carry risk even when made with pasteurized milk, so those are best avoided too. Raw sprouts (alfalfa, bean) are another quiet risk. And wash all fresh fruits and vegetables thoroughly, including pre-bagged lettuce.
High-Mercury Fish to Skip
Fish is actually encouraged during pregnancy for its omega-3 fatty acids and protein, but certain large, long-lived species accumulate mercury levels high enough to damage a developing nervous system. The FDA lists seven fish to avoid completely:
- King mackerel
- Marlin
- Orange roughy
- Shark
- Swordfish
- Tilefish from the Gulf of Mexico
- Bigeye tuna
Safe options you can eat two to three servings per week include salmon, shrimp, cod, tilapia, catfish, sardines, canned light tuna, and pollock. Albacore (white) tuna has more mercury than light tuna, so limit it to one serving per week.
Alcohol and Caffeine
No amount of alcohol has been shown to be safe during pregnancy. Alcohol crosses the placenta freely and can interfere with organ development at any point, but the first trimester is when the brain and central nervous system are taking shape. The safest approach is zero alcohol throughout pregnancy.
Caffeine is a different story. Moderate intake, defined as less than 200 mg per day, does not appear to be a major contributing factor in miscarriage or preterm birth. Above 200 mg per day, the risk of miscarriage roughly doubles. For reference, 200 mg is about one 12-ounce cup of brewed coffee. Keep in mind that tea, soda, chocolate, and energy drinks all contribute to your daily total.
Medications to Be Careful With
Ibuprofen (Advil, Motrin), naproxen (Aleve), aspirin, and other anti-inflammatory painkillers (NSAIDs) should generally be avoided during pregnancy. After 20 weeks, NSAIDs can cause kidney problems in the baby and dangerously low amniotic fluid levels. Earlier in pregnancy, the risks are less well defined but most providers recommend steering clear. The one exception is low-dose aspirin (81 mg), which is sometimes prescribed specifically for pregnancy-related conditions.
Acetaminophen (Tylenol) remains available for pain and fever during pregnancy. Beyond pain relievers, many common medications, including certain acne treatments, anti-anxiety drugs, and herbal supplements, may not be safe in the first trimester. Before taking anything new, including over-the-counter medications and supplements, check with your provider or pharmacist.
Skincare Ingredients to Swap Out
Retinoids are the big one. Prescription retinoids (tretinoin, isotretinoin) and over-the-counter retinol are all forms of vitamin A that can cause birth defects when absorbed in high amounts. Stop using any retinoid-based product as soon as you know you’re pregnant, or ideally when you start trying to conceive.
Hydroquinone, a skin-lightening ingredient, has a higher absorption rate than most topical chemicals, meaning more of it reaches your bloodstream. It falls into a category where safety during pregnancy hasn’t been established. High-concentration aluminum chloride, found in some clinical-strength antiperspirants, is another ingredient worth swapping for a lower-concentration alternative. When in doubt, simplify your routine and check labels for these ingredients.
Hot Tubs, Saunas, and Overheating
Raising your core body temperature too high in the first trimester increases the risk of neural tube defects like spina bifida. Studies show that exposure to hot tub water at 101°F or higher doubles the risk from about 1 in 1,000 to 2 in 1,000. That may sound small, but it’s an entirely preventable risk. Avoid hot tubs and saunas during the first trimester. Warm baths are fine as long as the water isn’t hot enough to raise your body temperature significantly.
Exercise You Should Modify
Exercise during pregnancy is healthy and encouraged, but the type matters. Contact sports like soccer, basketball, and martial arts carry the risk of a blow to the abdomen. Activities with a high fall risk, such as skiing, horseback riding, and gymnastics, become more dangerous as pregnancy shifts your center of gravity and loosens your joints. Even in the first trimester, your balance and stability are already beginning to change.
Avoid jerky, bouncy, or high-impact movements that increase your chance of injury. Walking, swimming, stationary cycling, and prenatal yoga are all good alternatives that keep you active without the added risk.
Cat Litter and Household Chemicals
Toxoplasmosis is a parasitic infection that can cause serious problems in a developing baby, and one way it spreads is through cat feces. The key detail: this only applies to cats that go outdoors and hunt prey like mice. If your cat is strictly indoors and eats only commercial cat food, your risk is very low. If your cat does go outside, have someone else handle litter box duties daily. The parasite becomes infectious one to five days after it’s shed, so daily cleaning reduces the window of exposure.
For household cleaning, the main concern is chemical fumes in poorly ventilated spaces. Wear gloves, open windows and doors, and avoid inhaling sprays directly. Paint and volatile solvents deserve extra caution, so keep any room well ventilated during and after use. Spray tans are also best avoided because of the risk of inhaling the mist.
Dental Care Is Still Safe
One common worry you can let go of: dental visits. Dental X-rays and local anesthesia are considered safe at any stage of pregnancy, including the first trimester. The American Dental Association no longer recommends abdominal or thyroid shielding during dental X-rays for pregnant patients because the radiation exposure is so minimal. Skipping dental care, on the other hand, can allow gum disease to progress, which has its own links to pregnancy complications. Keep your appointments.