Several commonly used herbs pose real risks during pregnancy, from triggering uterine contractions to interfering with fetal development. The challenge is that most herbs have never been formally tested in pregnant women, so the default guidance from organizations like the Mayo Clinic is cautious: avoid herbal teas and supplements unless your provider has specifically cleared them. That said, some herbs carry well-documented dangers that go beyond general caution.
Herbs That Can Trigger Contractions or Miscarriage
A handful of herbs have direct effects on the uterus. They appear to work through mechanisms similar to those used in medical pregnancy termination: either blocking progesterone (the hormone that sustains early pregnancy) or stimulating the uterine wall to contract. These are not theoretical risks.
Pennyroyal is one of the most dangerous. Its active compound is highly toxic to the liver. Ingestion causes nausea, vomiting, and abdominal pain initially, but can progress to liver and kidney failure, seizures, and death. The National Capital Poison Center has documented cases of multi-organ failure after pennyroyal oil ingestion. This herb should never be consumed during pregnancy in any amount, including as a tea.
Blue cohosh has a long history of use as a labor-inducing remedy, and it’s sometimes confused with black cohosh. Blue cohosh is identified in toxicology literature as a herbal abortifacient alongside pennyroyal and rue. It has been linked to serious complications in newborns, including heart problems, when taken near the end of pregnancy.
Rue is another traditional abortifacient that stimulates uterine activity. It remains available as a garden herb and in some herbal preparations, making accidental exposure a concern.
Herbs That Affect Fetal Development
Some herbs don’t cause contractions but can interfere with how your baby develops. The risks here are subtler and sometimes don’t show up until after birth.
Goldenseal and other berberine-containing herbs (like Oregon grape and barberry) are a concern because berberine is extremely effective at displacing bilirubin in the blood. In lab studies, berberine displaced bilirubin from blood proteins about ten times more powerfully than well-known pharmaceutical displacers. In a newborn, excess free bilirubin can cross into the brain and cause a dangerous form of jaundice. This is why berberine-containing supplements are consistently flagged as unsafe during pregnancy.
Licorice root is found in many herbal teas and candies, and its active compound (glycyrrhizin) appears to disrupt how the body regulates cortisol, the stress hormone. Some cortisol is necessary for fetal development, but too much can be harmful. A study tracking children born to mothers who consumed large amounts of licorice during pregnancy (about 9 ounces per week) found those children scored lower on cognitive tests of reasoning and memory and showed more signs of ADHD. Glycyrrhizin has also been linked to blood pressure spikes, shorter pregnancies, and dangerous drops in potassium levels. Licorice root is an ingredient in many herbal tea blends, so check labels carefully.
Herbs With Hormonal Effects
Pregnancy depends on a precise hormonal balance. Herbs containing plant-based estrogens (phytoestrogens) can potentially interfere with that balance by binding to estrogen receptors in both your body and your developing baby’s brain.
Soy products contain high levels of phytoestrogens like genistein and daidzein. After consuming soy protein, measurable concentrations of these compounds appear in the bloodstream. Because their chemical structure closely resembles the body’s own estrogen, they can activate estrogen receptors in the developing brain during critical windows of growth. While moderate dietary soy is generally considered low-risk, concentrated soy isoflavone supplements are a different story and are best avoided during pregnancy.
Herbs like dong quai, red clover, and fennel seed also have estrogenic activity. In supplement or medicinal doses, they could theoretically shift the hormonal environment enough to cause problems. As teas or food seasonings in small amounts, the exposure is much lower, but concentrated capsules or extracts carry greater risk.
The Difference Between Cooking and Supplementing
This is where many people get confused. A pinch of rosemary on roasted chicken is not the same as taking a rosemary supplement. The American Pregnancy Association makes this distinction explicit: rosemary has “Generally Recognized as Safe” status as a food ingredient, but in medicinal doses it can stimulate uterine activity and menstrual flow.
The same principle applies to garlic, sage, ginger, and turmeric. All are safe in the amounts you’d normally use while cooking. All could be problematic in the concentrated doses found in capsules, extracts, or therapeutic teas brewed to medicinal strength. If you’re sprinkling turmeric into a curry, that’s fine. If you’re taking turmeric capsules with standardized curcumin extract, that’s a different level of exposure entirely.
A practical rule: if you’re consuming an herb the way you’d use it in a recipe, the risk is generally very low. If you’re taking it as a supplement, tincture, essential oil, or strong concentrated tea specifically for its health effects, treat it with much more caution.
Red Raspberry Leaf: Timing Matters
Red raspberry leaf tea is one of the most popular herbal remedies in pregnancy, often promoted for toning the uterus before labor. But timing matters significantly. Most midwives advise avoiding it entirely during the first trimester because of its effects on uterine muscle. The typical recommendation is to start no earlier than 32 to 34 weeks, when the uterus is well developed and the tea is less likely to cause cramping. Even then, moderation is important, and it’s not appropriate for every pregnancy, particularly those with complications.
Herbal Teas Deserve Extra Scrutiny
Herbal teas feel harmless because they’re sold alongside regular groceries, but they can contain ingredients that are genuinely risky during pregnancy. Hibiscus tea, for instance, has been shown in animal studies to have estrogenic effects, and some practitioners recommend avoiding it. Licorice root appears in many “throat coat” and digestive tea blends without being prominently featured on the front label.
The broader problem is that herbal supplements and teas aren’t regulated the same way pharmaceuticals are. Labels may list proprietary blends without specifying how much of each ingredient is included. A “pregnancy tea” on the shelf isn’t necessarily vetted by any regulatory body. Read ingredient lists carefully, and be skeptical of blends that list many botanicals without clear dosing information.
Quick Reference: Herbs To Avoid
- Pennyroyal: Liver toxin and uterine stimulant. Dangerous in any amount.
- Blue cohosh: Uterine stimulant linked to newborn heart complications.
- Rue: Traditional abortifacient that stimulates contractions.
- Goldenseal, Oregon grape, barberry: Contain berberine, which can worsen newborn jaundice.
- Licorice root (in large amounts): Disrupts cortisol regulation, linked to cognitive effects in children and blood pressure problems.
- Dong quai: Strong estrogenic and uterine-stimulating effects.
- High-dose rosemary, sage, or turmeric: Safe in food, potentially harmful in supplement form.
- Red raspberry leaf (first trimester): Can cause uterine cramping early in pregnancy.
- Concentrated soy isoflavone supplements: Estrogenic activity that may affect fetal brain development.
If you’re unsure about a specific herb, the safest approach is to check whether you’re consuming it in a food-level amount or a medicinal-level amount. That single distinction accounts for most of the safety difference between herbs that are fine during pregnancy and herbs that aren’t.