Early pregnancy is when your baby’s major organs, brain, and spinal cord are forming, which makes the first trimester the window where certain exposures carry the most risk. Knowing what to skip during these weeks can help you avoid preventable problems like birth defects, miscarriage, and infections. Here’s what to steer clear of and why it matters.
Medications That Aren’t Pregnancy-Safe
Common painkillers like ibuprofen and naproxen (NSAIDs) are not considered safe in early pregnancy. A large meta-analysis of 38 studies found that NSAID use during early pregnancy was linked to a 28% increased risk of congenital anomalies overall and a 19% increased risk of major birth defects. Ibuprofen specifically was associated with a higher chance of congenital heart defects. Acetaminophen (Tylenol) is generally the recommended alternative for pain and fever, but check with your provider before taking anything new.
Acne medications containing retinoids (like isotretinoin) are well-known to cause severe birth defects. Preformed vitamin A in supplement form carries a similar risk at high doses. Some studies link doses above 10,000 IU per day to birth defects, while others place the threshold closer to 20,000 IU per day. The safest approach is to stick with your prenatal vitamin, which contains beta-carotene (the plant-based form of vitamin A) rather than preformed retinol, and avoid separate vitamin A supplements unless directed otherwise.
Alcohol, Smoking, and Caffeine Limits
No amount of alcohol has been shown to be safe during pregnancy. Alcohol crosses the placenta freely, and during the first trimester it can interfere with organ development and increase the risk of fetal alcohol spectrum disorders. The same applies to smoking and vaping, which restrict blood flow to the placenta and raise the chance of miscarriage, preterm birth, and low birth weight.
Caffeine doesn’t need to be eliminated entirely, but it should be capped at 200 milligrams per day, the limit recommended by the American College of Obstetricians and Gynecologists. That’s roughly one 12-ounce cup of brewed coffee. Keep in mind that caffeine also shows up in tea, chocolate, some sodas, and certain medications, so you need to count all sources together.
Foods That Carry Infection Risk
Listeria is the biggest food safety concern in pregnancy because it can cross the placenta and cause miscarriage or stillbirth even when your own symptoms are mild. The CDC specifically flags these higher-risk foods:
- Soft cheeses made from unpasteurized milk: brie, camembert, blue-veined cheese, queso fresco, queso blanco, and requesón
- Any queso fresco-type cheese, even when made with pasteurized milk, because of how it’s produced
- Unpasteurized (raw) milk and dairy products made from it
- Deli meats and unheated deli-sliced cheese, unless heated until steaming
Raw or undercooked eggs, meat, and seafood also pose risks from salmonella and toxoplasmosis. Cook eggs until both the yolk and white are firm, and bring all meat and fish to safe internal temperatures.
High-Mercury Fish to Avoid Entirely
Mercury accumulates in large, long-lived predatory fish and can damage a developing baby’s brain and nervous system. The FDA lists seven types of fish to skip completely during pregnancy: king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish, and bigeye tuna. Lower-mercury fish like salmon, sardines, tilapia, and shrimp are safe and actually beneficial. Aim for two to three servings a week of these options to get omega-3 fatty acids that support fetal brain development.
Hot Tubs, Saunas, and Overheating
Raising your core body temperature above 39°C (about 102.2°F) during the first trimester has been linked to an increased risk of neural tube defects like spina bifida. Hot tubs and saunas can push your temperature past this threshold quickly, sometimes within 10 to 20 minutes, because unlike exercise, your body can’t cool itself effectively in hot water or a heated room. Warm baths are fine as long as the water isn’t hot enough to make your skin red or cause you to sweat. If you exercise, stay hydrated and avoid pushing to the point of overheating.
Cat Litter and Toxoplasmosis
Toxoplasmosis is a parasitic infection that can cause serious brain and eye damage in a developing baby. The parasite is shed in cat feces and becomes infectious one to five days after it leaves the cat. The FDA recommends having someone else handle litter box duties during pregnancy. If that’s not possible, wear disposable gloves and wash your hands thoroughly afterward. Change the litter daily so the parasite doesn’t have time to become infectious.
The same precautions apply to gardening and sandboxes, since outdoor cats use soil and sand as litter. Wear gloves, wash your hands, and cover sandboxes when they’re not in use. Keep your cat indoors, feed only commercial food (never raw meat), and avoid adopting a new cat until after delivery.
Household Chemicals and Solvents
Organic solvents and chlorinated solvents have been linked to birth defects, miscarriage, and low birth weight. These chemicals show up in more places than you might expect: paint thinner, turpentine, nail polish remover, some heavy-duty cleaners, dry cleaning fluid, and adhesives. The CDC lists toluene, benzene, xylene, and perchloroethylene among the common solvents associated with reproductive harm.
If you’re painting a nursery or refinishing furniture, let someone else handle it, or at minimum work in a well-ventilated space with windows open. Switch to fragrance-free, plant-based cleaners for everyday use. Avoid spending time in recently dry-cleaned spaces or freshly painted rooms where fumes linger.
Exercise to Skip (and What’s Still Safe)
Exercise itself is encouraged during pregnancy, but certain activities carry too high a risk of falls or abdominal trauma. ACOG advises avoiding contact sports like ice hockey, boxing, soccer, and basketball. Activities with a significant fall risk are also on the list: downhill skiing, water skiing, surfing, off-road cycling, gymnastics, horseback riding, and skydiving. Scuba diving is off-limits because the pressure changes can cause gas bubbles in your baby’s blood. Activities above 6,000 feet elevation are discouraged unless you already live at altitude.
Walking, swimming, stationary cycling, prenatal yoga, and light strength training are all considered safe. There’s no official weight limit for lifting during pregnancy, but the general guidance is to use weights that feel light to moderate rather than heavy, focus on technique over load, and avoid holding your breath. Tighten your pelvic floor before lifting, keep your back straight, and stop if you feel faint, overheated, or in pain.
Substance Exposure and X-Rays
Recreational drugs, including marijuana, carry risks during early pregnancy. THC crosses the placenta, and its use in the first trimester has been associated with lower birth weight and developmental concerns. Diagnostic X-rays at the dentist or doctor’s office are generally considered low risk with proper shielding, but elective imaging should be postponed when possible. Let any healthcare provider know you’re pregnant before they order scans or prescribe medications.
Stress and Sleep Deprivation
Chronic, high-level stress floods your body with cortisol, which can affect blood flow to the placenta and has been associated with preterm birth. You can’t eliminate all stress, but sustained sleep deprivation compounds the problem. Prioritizing seven to nine hours of sleep per night supports the immune and hormonal shifts your body is navigating. If nausea or anxiety is disrupting your sleep in the first trimester, even short daytime rest can help buffer the effects.