Early pregnancy is when your baby’s major organs, brain, and spinal cord are forming, which makes the first trimester a window where certain foods, substances, and activities carry outsized risk. Knowing what to skip during these weeks can feel overwhelming, but the list is more manageable than it seems. Here’s what actually matters and why.
Alcohol Has No Safe Threshold
There is no known safe amount of alcohol during pregnancy, and there is no safe trimester to drink it. The CDC is unambiguous on this point. Alcohol use in the first three months can cause abnormal facial features in the baby, while growth and central nervous system problems, including low birthweight and behavioral issues, can result from exposure at any point. The baby’s brain develops throughout the entire pregnancy and remains vulnerable to alcohol the whole time.
High-Mercury Fish
Fish is healthy during pregnancy. The FDA recommends 8 to 12 ounces per week of lower-mercury seafood, which works out to two or three 4-ounce servings. What you want to avoid entirely are the seven highest-mercury species: king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish, and bigeye tuna. Mercury at high levels can damage a developing nervous system.
Lower-mercury options like salmon, shrimp, tilapia, and canned light tuna are all on the FDA’s “Best Choices” list and are safe to eat regularly.
Foods That Carry Listeria Risk
Listeria is a bacteria that’s relatively harmless to most adults but can cause miscarriage, stillbirth, or serious infection in a newborn. Pregnant women are significantly more susceptible to it, and the foods most likely to harbor it are specific enough to memorize.
The main ones to avoid:
- Deli meat, hot dogs, and cold cuts unless heated until steaming. This includes fermented or dry sausages and refrigerated pâté or meat spreads.
- Soft cheeses made from unpasteurized (raw) milk, such as brie, camembert, and blue-veined cheese. Also avoid any queso fresco-type cheese (queso blanco, requesón, and similar fresh soft cheeses) regardless of whether the milk was pasteurized, as well as unheated cheese sliced at a deli counter.
- Raw or unpasteurized milk and any dairy products made from it.
- Raw sprouts of any kind, including alfalfa and bean sprouts.
- Unwashed fruits and vegetables, including leafy greens. Always rinse produce thoroughly.
- Cut melon left out for more than two hours (one hour if the temperature is above 90°F).
Caffeine: Stay Under 200 mg
You don’t have to give up coffee entirely. The widely accepted guideline, endorsed by the American College of Obstetricians and Gynecologists, the UK National Health Service, and the European Food Safety Authority, is to keep caffeine below 200 mg per day. That’s roughly one 12-ounce cup of brewed coffee or two cups of black tea.
Keep in mind that caffeine adds up from multiple sources: chocolate, certain sodas, energy drinks, and green tea all contribute. Some recent research has questioned whether even 200 mg is truly risk-free, so staying well under that limit gives you the widest safety margin.
Common Pain Relievers to Skip
Ibuprofen and other anti-inflammatory pain relievers (the class that includes naproxen and aspirin) interfere with compounds your body uses for embryo implantation, placental development, and maintaining the pregnancy. These drugs cross the placental barrier and enter fetal circulation. A large meta-analysis found that ibuprofen use in early pregnancy was associated with an elevated risk of congenital heart defects and a specific abdominal wall defect called gastroschisis.
Acetaminophen (Tylenol) is generally considered the safer alternative for pain and fever during pregnancy, though using it only when truly needed and at the lowest effective dose is the standard advice.
Too Much Vitamin A
Vitamin A in its active form (retinol, found in supplements and liver) is essential in small amounts but dangerous in excess. The European Food Safety Authority sets the upper limit at 3,000 micrograms per day for women of childbearing age, while the UK’s Expert Committee on Vitamins and Minerals considers anything above 1,500 micrograms per day inappropriate due to bone and fetal effects.
Excess vitamin A can cause a range of birth defects: spina bifida, cleft palate, limb deformities, heart defects, and malformations of the ears, eyes, and kidneys. The practical takeaway is to avoid high-dose vitamin A supplements, skip liver and liver products (which are extremely concentrated sources), and check your prenatal vitamin to make sure its vitamin A comes from beta-carotene rather than preformed retinol. Beta-carotene, the form found in carrots and sweet potatoes, is converted by your body only as needed and doesn’t carry the same risk.
Skincare Ingredients Worth Checking
Oral retinoids, prescription medications containing high-dose vitamin A derivatives taken by mouth, are well established as causing birth defects and are strictly avoided in pregnancy. Topical retinoids in skincare (tretinoin, retinol, adapalene) are a different story. A study in The Lancet that followed 215 women exposed to topical tretinoin in the first trimester found no increased risk of major congenital anomalies compared to unexposed women.
That said, most dermatologists and OB-GYNs still recommend stopping topical retinoids during pregnancy out of an abundance of caution, since the oral form is so clearly harmful. If you’re using a retinol cream or prescription tretinoin for acne, switching to pregnancy-safe alternatives like azelaic acid is a simple swap that avoids the question entirely.
Heat Exposure and Hot Tubs
Raising your core body temperature too high during the first trimester is linked to neural tube defects like spina bifida and anencephaly. Hot tubs, saunas, and steam rooms are the primary culprits because they can push your body temperature up quickly and keep it elevated.
If you want to take a bath, keeping the water at or below 99°F (37°C) prevents a meaningful rise in core temperature. Hot yoga and hot Pilates fall into the same category and should be swapped for their regular-temperature versions.
Physical Activities With Fall or Impact Risk
Exercise during pregnancy is encouraged, but certain activities become riskier for specific reasons. Pregnancy hormones loosen the ligaments that support your joints, making them more mobile and easier to injure. As your body changes, your center of gravity shifts forward, increasing your risk of losing balance.
ACOG recommends avoiding:
- Contact sports where you could be hit in the abdomen: ice hockey, boxing, soccer, basketball
- Activities with fall risk: downhill skiing, water skiing, surfing, off-road cycling, gymnastics, horseback riding
- Scuba diving, which exposes the baby to decompression pressure
- Skydiving
- Exercise above 6,000 feet if you don’t already live at high altitude
Walking, swimming, stationary cycling, and prenatal yoga are all safe and effective alternatives that keep you active without the added risks. Avoid standing motionless for long periods, which can cause blood to pool in your legs and temporarily drop your blood pressure.
Smoking and Secondhand Smoke
Smoking during pregnancy restricts oxygen and nutrient delivery to the developing baby. It raises the risk of miscarriage, preterm birth, low birthweight, and placental complications. Secondhand smoke carries many of the same risks, so avoiding enclosed spaces where others are smoking matters too. Vaping and nicotine replacement products also deliver nicotine to the fetus, which affects brain and lung development.
Putting It All Together
Most of these changes come down to a handful of habits: switching your pain reliever, checking supplement labels, reheating deli meat, choosing lower-mercury fish, and skipping alcohol. The list feels long on paper, but in daily life it’s a short set of swaps rather than a complete overhaul. A good prenatal vitamin with folate, a balanced diet from well-cooked and well-washed foods, and moderate exercise cover most of what your body needs during these early weeks.