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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

Not Advised in Pregnancy

Alcohol, Excess Caffeine, and High-Risk Herbs

Evidence grade 3 of 5, Mixed. Read how the Atlas grades evidence.

0 human trials, about 4 studies, Guideline consensus (CDC, ACOG, Surgeon General). The written rationale for this grade is still being prepared.

FDA
Mix of substances; alcohol carries federal warning labels
WADA
Varies

Reference only. Not medical advice.

What can go wrong

The items on this list are themselves the risk, which makes it different from the rest of the library. Alcohol can affect fetal brain development at any stage of pregnancy with no established safe threshold, and the resulting fetal alcohol spectrum disorders are lifelong. Caffeine above roughly 200 mg a day has been associated in some studies with miscarriage and low birth weight, though the evidence is debated, which is why the mainstream guidance is a moderate limit rather than zero. Several uterotonic herbs, including blue and black cohosh, can stimulate contractions or cause cardiovascular harm. High-dose preformed vitamin A is teratogenic, high-mercury fish can damage the developing nervous system, and unpasteurized dairy and some ready-to-eat meats carry a listeria risk that is far more dangerous in pregnancy. Detox and weight-loss supplements are unregulated before sale and have been found adulterated with hidden drugs, so they belong in the avoid column outright. This list is a starting point, not a substitute for care. Confirm every supplement, medication, herbal product, and food question with your own obstetric provider, who may add items based on your history and prescriptions.

Most prenatal nutrition is about what to add. This entry is about what to keep out, and it is one of the clearer corners of the guidance. Alcohol has no known safe amount in pregnancy and is the leading preventable cause of birth defects and developmental disability, the group of outcomes called fetal alcohol spectrum disorders. ACOG advises keeping caffeine under about 200 mg a day. High doses of preformed vitamin A are teratogenic, and a number of uterus-stimulating herbs sold as gentle, including blue and black cohosh, are considered unsafe. The FDA and EPA name specific high-mercury fish to avoid, and food-safety agencies flag unpasteurized dairy and certain deli items for listeria risk. These are not nutrients to optimize but exposures to minimize. Because personal history and medications change the list, every supplement and food question here is one to confirm with your own obstetric provider.

The short, well-evidenced list of things to keep out of a pregnancy, where the guidance is unusually clear.

What people take it for

These are the reasons people give for taking it. They are not effects it has been shown to have.

  • Knowing which exposures to minimize or avoid before and during pregnancy
  • Distinguishing a firm avoid, such as alcohol, from a moderate limit, such as caffeine
  • Recognizing uterus-stimulating herbs that clean-looking labels will not warn about
  • Reading the FDA and EPA fish list so lower-mercury seafood stays on the plate
  • Understanding why unpasteurized dairy and certain deli items carry a listeria caution
  • Treating detox and weight-loss supplements as a category to avoid rather than evaluate

What people get wrong

  • Often saidA little alcohol, like an occasional glass of wine, is safe in pregnancy.

    ActuallyThe major US authorities, including the CDC, ACOG, the American Academy of Pediatrics, and the US Surgeon General, state there is no known safe amount of alcohol and no safe time to drink during pregnancy. Because no threshold has been established and the harms are serious and permanent, the consistent advice is none. The CDC also associates prenatal alcohol with higher risk of miscarriage, stillbirth, preterm birth, and SIDS.

  • Often saidCaffeine has to be cut out completely.

    ActuallyThe mainstream guidance is moderation, not elimination. ACOG Committee Opinion No. 462 advises keeping caffeine under about 200 mg a day, roughly one 12-ounce cup of coffee, and holds that moderate intake is not a major contributor to miscarriage or preterm birth. A minority view, argued by James in a 2020 review of 48 studies, contends no safe level exists. The disagreement is real and worth raising with your provider rather than settling from a headline.

  • Often saidHerbal means gentle, so pregnancy teas and tinctures are the safe choice.

    ActuallySome of the herbs marketed as natural are the specific ones to avoid. Blue cohosh contains constituents with oxytocic and cardiovascular activity, and case reports describe serious heart injury in newborns after mothers used it to bring on labor, per NIH's LactMed database. A clean-looking supplement label carries no requirement to warn about this.

  • Often saidVitamin A is just a vitamin, so more must be better in pregnancy.

    ActuallyPreformed vitamin A, the retinol form, is teratogenic at high doses. NIH's Office of Dietary Supplements sets the pregnancy upper limit at 3,000 mcg RAE (about 10,000 IU) per day and advises against high-dose supplements. Beta-carotene, the plant-derived provitamin form, is not known to be teratogenic, which is an important distinction.

Who profits, and who pushes back

  • CDC & US Surgeon General

    championsFederal public-health authorities

    There is no known safe amount of alcohol use during pregnancy or while trying to get pregnant, and no safe time; alcohol can cause fetal alcohol spectrum disorders, which are preventable.

  • ACOG

    endorsesUS obstetric authority

    Moderate caffeine consumption (less than 200 mg per day) does not appear to be a major contributing factor in miscarriage or preterm birth; intake should be kept at or below that level.

  • Herbal-safety references

    cautionsNatural Medicines / teratology literature

    Uterus-stimulating herbs such as blue cohosh and black cohosh, and various others, are considered unsafe in pregnancy and can cause contractions, bleeding, or fetal harm.

  • Caffeine-evidence dissent

    mixedSome researchers

    A minority view argues even moderate caffeine may carry risk and that no clearly safe level is established, though mainstream guidance retains the 200 mg threshold.

Where the research comes from

Most of the published research on this comes from one place. 100% of it is from Clear guidance. Findings that no unrelated group has reproduced are weaker than the study count makes them look.

Share of published research by country of origin.
PlaceShare of published research
Clear guidance100%

Research published from: Global.

How we got here

Avoid-lists in pregnancy took their modern shape across the 20th century, as specific harms moved from folk suspicion to documented cause. Warnings against drinking in pregnancy appear in far older traditions, including references in ancient Greek and Talmudic writing and long-standing caution in many cultures, but the clinical picture was named in 1973, when Jones and Smith described fetal alcohol syndrome in Seattle. That description reframed alcohol from a vague worry into a defined, preventable condition and led to US warning labels in 1988. Herbal uterotonics have an even longer and more global story. Blue cohosh (Caulophyllum thalictroides) was used by Native American nations, including the Iroquois and other Eastern Woodlands peoples, and later adopted by North American midwives to bring on labor, which is precisely why its cardiovascular toxicity in newborns now draws caution. Vitamin A teratogenicity was pinned down by prospective research in the 1990s, and mercury and listeria advisories were formalized by federal agencies as monitoring improved.

  1. 1973Jones and Smith describe fetal alcohol syndrome in The Lancet, giving alcohol harm in pregnancy a clinical name
  2. 1988US law mandates alcohol warning labels citing the risk of birth defects
  3. 1995Rothman and colleagues publish the NEJM cohort linking high-dose preformed vitamin A to cranial birth defects
  4. 2010ACOG issues Committee Opinion No. 462, setting the under-200 mg per day caffeine guidance
  5. 2019FDA warns that the supplement ingredient vinpocetine, found in some memory and weight-loss products, may cause miscarriage and fetal harm
  6. 2020James publishes a review in BMJ Evidence-Based Medicine arguing no safe level of caffeine exists in pregnancy; ACOG reaffirms its moderate-limit guidance
  7. 2021FDA and EPA release updated joint fish advice naming seven highest-mercury fish to avoid

At a glance

Alcohol
No known safe amount
Caffeine
Limit ~200 mg/day
Preformed vitamin A
Stay under 3,000 mcg
High-risk herbs
Cohosh, others

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about Not Advised in Pregnancy. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.

Sources