At five weeks pregnant, your embryo’s brain, spinal cord, and heart are actively forming, making this one of the most sensitive windows of the entire pregnancy. What you eat, apply to your skin, and expose yourself to matters more right now than it will later. Here’s a specific, practical guide to what to steer clear of.
Why Week 5 Is Especially Sensitive
By the fifth week, the neural tube (which becomes the brain and spinal cord) is taking shape, and a tiny heart tube is already pulsing around 110 times per minute. Most major birth defects originate during the first trimester, when organs and body systems are being built from scratch. The risk of miscarriage also drops significantly once this critical formation period is complete. That’s the context behind every item on this list: the things that matter most to avoid are the ones that can interfere with this rapid, delicate construction.
Foods That Carry Infection Risk
Pregnant women are 10 times more likely than the general population to get a Listeria infection, a type of food poisoning that can cause miscarriage. Toxoplasmosis, another foodborne parasite, poses similar risks. Both are easy to avoid once you know where they hide.
Skip these entirely:
- Deli meats, hot dogs, and cold cuts unless heated until steaming. Listeria thrives in refrigerated, ready-to-eat meats.
- Soft cheeses like brie, camembert, blue cheese, queso fresco, and queso blanco. Even versions made with pasteurized milk carry risk for fresh, soft varieties like queso fresco.
- Raw or runny eggs, including foods that contain them: homemade Caesar dressing, raw cookie dough, homemade eggnog, and cake batter.
- Raw or undercooked meat and poultry. Use a meat thermometer and cook to the recommended internal temperature.
- Raw fish and shellfish, including sushi, sashimi, and ceviche.
- Refrigerated smoked seafood labeled as lox, nova-style, kippered, or smoked (fine if cooked into a dish).
- Raw sprouts like alfalfa and bean sprouts, which are common carriers of bacteria.
- Unpasteurized milk, juice, or cider.
- Raw flour, which can harbor E. coli. That includes tasting raw dough or batter of any kind.
Wash all fresh fruits and vegetables thoroughly, including pre-bagged lettuce. Cut melon shouldn’t sit out longer than two hours (one hour if temperatures are above 90°F).
High-Mercury Fish
Mercury accumulates in certain large, long-lived fish and can damage a developing nervous system. The FDA lists seven fish to avoid completely during pregnancy:
- Shark
- Swordfish
- King mackerel
- Tilefish (Gulf of Mexico)
- Marlin
- Orange roughy
- Bigeye tuna
Other fish are fine and even encouraged for their omega-3 content. Salmon, sardines, shrimp, and canned light tuna are all lower-mercury options.
Caffeine
Current guidelines from major health organizations set the limit at 200 mg of caffeine per day, roughly one 12-ounce cup of home-brewed coffee. Some research has linked even amounts below that threshold to higher rates of pregnancy loss and low birth weight, so less is generally better. Keep in mind that caffeine adds up from multiple sources: tea, chocolate, soda, and energy drinks all contribute. If you’re a heavy coffee drinker, tapering down rather than quitting abruptly can help manage withdrawal headaches.
Over-the-Counter Pain Relievers
Ibuprofen (Advil, Motrin) and other anti-inflammatory painkillers are not considered safe in early pregnancy. Some studies have linked ibuprofen use around the time of conception or during the first trimester to a higher chance of miscarriage. A small increased risk of heart defects and a rare abdominal wall defect called gastroschisis have also been reported, though the absolute increase is less than 1%. Acetaminophen (Tylenol) is the pain reliever most commonly considered acceptable during pregnancy, but check with your provider about dosing if you’re relying on it frequently.
Vitamin A and Supplements
Preformed vitamin A (the type found in liver, some supplements, and fortified foods) becomes dangerous at high doses, particularly during the first 60 days of fetal development, which is right where you are now. The WHO sets the upper limit at 10,000 IU per day. Doses above that carry a real risk of birth defects, and intake above 25,000 IU per day has been specifically linked to urinary tract malformations.
A standard prenatal vitamin contains a safe amount, usually in the form of beta-carotene, which your body converts only as needed. The concern is with taking additional vitamin A supplements on top of your prenatal, eating liver frequently (which can contain extremely high levels), or using acne supplements that contain retinol. Check your supplement labels and avoid stacking multiple products that each contain vitamin A.
Skincare Ingredients
If your medicine cabinet includes any anti-aging or acne products, check the labels for retinoids. Topical tretinoin (Retin-A), adapalene, and other vitamin A derivatives should be stopped. Although the amount absorbed through skin is low, case reports of birth defects consistent with retinoid exposure exist, and there’s no reason to take the risk when alternatives are available.
Hydroquinone, a skin-lightening ingredient, is also worth shelving. It has a relatively high absorption rate compared to other topical products, meaning more of it enters your bloodstream. Most other common skincare ingredients, including gentle cleansers, moisturizers, sunscreen, and topical antibiotics prescribed for acne, act locally on the skin and produce minimal systemic levels.
Alcohol and Smoking
No amount of alcohol has been established as safe during pregnancy, and week 5 falls squarely in the period when the brain and central nervous system are forming. Alcohol crosses the placenta freely and can disrupt development at any dose. Smoking restricts oxygen and blood flow to the embryo. If you’re still smoking, even cutting down helps, but quitting entirely is the goal.
Cat Litter and Garden Soil
Toxoplasmosis is a parasitic infection that can cause serious harm to a developing baby, and cat feces are a primary transmission route. If you have a cat, have someone else handle the litter box for the duration of your pregnancy. If that’s not possible, wear disposable gloves and change the litter daily, since the parasite doesn’t become infectious until one to five days after it’s shed.
The same parasite can live in garden soil and sandboxes where cats have been. Wear gloves when gardening, wash your hands thoroughly afterward, and cover outdoor sandboxes. Don’t adopt a new cat while pregnant, and keep indoor cats indoors. Feed cats only commercial food, never raw meat, which can carry the parasite.
Certain Herbal Teas
Not all herbal teas are harmless. Several common herbs can stimulate uterine contractions or are directly toxic to a developing embryo. Avoid teas made from:
- Blue cohosh and black cohosh, which can trigger contractions and may be toxic to the fetus
- Pennyroyal, which is liver-toxic and has been historically used as an abortifacient
- Rue, which is toxic internally and can induce contractions
- Wormwood, which contains a potentially neurotoxic compound
- Castor oil, which can stimulate uterine contractions
Ginger tea and peppermint tea are generally considered safe and can help with the nausea that often kicks in right around week 5. If you’re browsing herbal blends at the store, check that the ingredients don’t include anything on the list above, since “pregnancy tea” branding isn’t regulated.
Hot Tubs and Saunas
Raising your core body temperature above 101°F during the first trimester has been associated with neural tube defects. Hot tubs, saunas, and steam rooms can push your temperature up quickly. Warm baths are fine as long as the water isn’t hot enough to make you flush or sweat. If you’re unsure, keep soaks brief and the temperature moderate.