A few herbs are known pregnancy risks, and most were never tested

Key takeaways

• A 2024 review of 111 studies from 51 countries found that about 34% of pregnant women used herbal medicines, but only about 28% of them told a health care provider¹.
• Pennyroyal oil, long used to bring on periods or end pregnancies, has caused deaths from liver and organ failure, and as little as a tablespoon can cause seizures or coma⁴⁵.
• In a Finnish study, teens whose mothers ate large amounts of licorice in pregnancy, about 250 grams a week, scored about 7 IQ points lower on reasoning tests, though the study can’t prove licorice was the cause⁷.
• A placebo-controlled trial of raspberry leaf tablets in 192 first-time mothers found no significant difference in labor outcomes such as emergency cesareans⁹.
• MotherToBaby, a service of the Organization of Teratology Information Specialists, answers questions about herbs and medicines by phone at 866-626-6847 or by text at 855-999-3525³.

When researchers pooled 111 studies from 51 countries in 2024, a pattern jumped out. About one in three pregnant women used herbal medicines¹.

Most kept it to themselves. Only about 28% of users told a doctor, midwife or nurse¹. The main reasons: women saw herbs as harmless, and no one asked¹.

That gap matters, because “natural” and “tested in pregnancy” are different things. A few herbs have well-documented harms. Many more have never been studied in pregnant women at all, which isn’t the same as being proven safe.

This guide sorts the herbs into those groups. It draws on what teratology services, the experts who study exposures in pregnancy, say. It also covers breastfeeding, where the questions are different.

Why pregnancy changes the question

Herbs may cross the placenta and pass into breast milk, so a remedy taken by a parent can reach the baby².

Use is common, too. Raspberry leaf was the most-used pregnancy herb in an 810-woman survey cited by Australian researchers, and nearly half the women in their own 2024 study used it¹⁰.

The products themselves add uncertainty. In the U.S., herbal products don’t have to prove safety or effectiveness before sale, and the label may not match what’s inside³. Some echinacea products have even been found contaminated with heavy metals such as lead³.

Tinctures bring a separate issue. They’re made with alcohol and can contain a meaningful amount of it³. Our guide to herbal preparation forms explains the alternatives.

It also helps to know the baseline. In any pregnancy, there’s a background chance of about 3% that a baby will have a birth defect³. A small study that finds “no increase” above that rate is reassuring, but it can miss a rare problem.

MotherToBaby, run by the Organization of Teratology Information Specialists, puts its general advice plainly. Its echinacea fact sheet advises against herbal products in pregnancy in general, unless a health care provider is directing and overseeing their use³.

Pennyroyal: a folk remedy for late periods with a deadly record

In folk medicine, pennyroyal was used to bring on menstruation and, in larger amounts, to end pregnancies⁴.

The oil is mostly pulegone, a compound the liver turns into toxins⁴. The National Institutes of Health’s LiverTox database says even a tablespoon of the oil can cause fainting, seizures, coma and sudden liver injury⁴.

The published cases are grim. A 1978 federal report described three women who took a quarter-ounce to an ounce of the oil in failed attempts to end a pregnancy; one died⁴. Memorial Sloan Kettering’s herb database counts at least 24 cases of toxicity, including several young women who died of organ failure after trying to end a pregnancy⁵. Our essential-oil dilution article tells the story of an 18-year-old who died this way in 1979.

Babies have been harmed too. In a 1996 report, two infants given home-remedy tea made with pennyroyal developed organ failure, and one died⁴⁵.

Memorial Sloan Kettering says there is no scientific evidence that pennyroyal brings on a period or ends a pregnancy, and that pregnant or breastfeeding women should not take it⁵. The dilution article also explains how pulegone attacks the liver.

Blue cohosh: a labor herb tied to newborn emergencies

Blue cohosh is a root that some midwives have used to help labor along. In a 1999 U.S. survey, 64% of certified nurse-midwives said they had used it during labor⁶.

A 2008 safety review in the Canadian Journal of Clinical Pharmacology collected what’s known⁶. Its authors included researchers from Toronto’s Hospital for Sick Children and the Canadian College of Naturopathic Medicine⁶. The plant contains alkaloids and saponins, and the reviewers noted that it may narrow the arteries that feed the heart⁶. Midwives reported nausea, more meconium (a baby’s first stool) in the fluid and brief spikes in the baby’s heart rate⁶.

The case reports are the worrying part:

• A newborn heart attack. In 1998, doctors described a baby born with a heart attack, severe heart failure and shock after the mother took blue cohosh to bring on contractions. Other causes were ruled out, and the baby recovered after weeks of critical care⁶.
• A baby who didn’t breathe at birth. A 1996 New Zealand report described a newborn with oxygen-starved organs and lasting brain damage after a birth helped along with blue and black cohosh⁶.
• A newborn stroke, with a twist. A 2004 case linked blue cohosh tea to a newborn’s stroke. A drug screen also flagged a cocaine byproduct in the baby and in the mother’s bottle of tea, though the doctors later suggested the test may have picked up a look-alike substance. The reviewers still counted blue cohosh as a suspect⁶.

Case reports can’t prove cause. Still, the reviewers found that the case for blue cohosh starting labor rests only on expert opinion and lab work⁶. They concluded it should be used with extreme caution, only under medical supervision, and not sold over the counter⁶.

Licorice: a Finnish study followed children to their teens

Licorice root shows up in candy, gum, syrups and some herbal teas⁸. Its active compound, glycyrrhizin, may be the problem in pregnancy.

According to a University of Helsinki news release, researchers there studied 378 teens, about 13 years old⁷. Some of their mothers had eaten more than 500 milligrams of glycyrrhizin a week during pregnancy, roughly 250 grams of licorice⁷. Others had eaten little or none⁷. Only 51 teens were in the high-exposure group, a science-news report on the study noted⁸.

Compared with lightly exposed peers, the high-exposure teens averaged about 7 points lower on IQ-style reasoning tests given by a psychologist, and memory tasks went worse for them, too⁷. Girls in that group reached puberty sooner, and parents described more ADHD-type behavior⁷. An earlier Finnish study had found poorer memory and vocabulary at age 8 in children exposed before birth⁸.

Why might that happen? Cortisol, a stress hormone, helps a fetus develop but can harm it in excess. Animal research suggests glycyrrhizin disables the enzyme that normally switches cortisol off⁷.

This was an observational study, so it shows a link, not proof. Glycyrrhizin is only one of many influences on a developing baby, the researchers noted, and no one can tell whether it shaped any single teen’s results⁷. Since 2016, Finland’s health institute has advised pregnant women against licorice, though a few licorice sweets now and then aren’t considered dangerous⁷.

Labels don’t have to say how much glycyrrhizin a product contains⁸. Our herbal tea guide covers licorice and blood pressure.

Raspberry leaf, echinacea and the reassuring-but-thin group

Raspberry leaf. This tea is traditionally used to help prepare for labor². Women use it in very different ways: in one older Sydney study, some started as early as 8 weeks, at anywhere from 1 to 8 cups a day or as tablets⁹.

A double-blind trial gave 192 first-time mothers either 2.4 grams a day of raspberry leaf tablets or a placebo, starting at 32 weeks⁹. It found no significant differences in labor outcomes such as emergency cesarean rates, and the dose appeared safe for mothers and babies⁹.

A 2024 Australian study of 91 first-time mothers found that raspberry leaf users needed fewer labor interventions¹⁰. But its authors warned that the sample was small and that selection bias and other hidden factors could explain the gap¹⁰. They also cautioned that seeing no harm in a small study doesn’t prove raspberry leaf is safe¹⁰. The study had no outside funding, and the lead author is a naturopath and midwife, which the paper discloses¹⁰.

In November 2024, the UK’s Committee on Toxicity, a government advisory panel, finished a review of raspberry leaf tea in pregnancy⁹. It judged the risk low but highly uncertain⁹. It noted case reports ranging from tiny skin bleeds to liver injury, with unclear causes, and lab data suggesting the leaf can slow enzymes that process some drugs⁹. Australia’s MotherSafe service sums it up: the few studies found raspberry leaf safe but ineffective, so it can’t be specifically recommended².

Echinacea. Small studies have found no rise in birth defects above the usual rate³. A study of more than 350 exposed pregnancies found no increase in preterm birth or low birth weight³. Animal studies raised a miscarriage question, but one small human study found no increased risk³.

Teas and ginger. MotherSafe considers herbal teas in moderation safe². Our ginger, chamomile and peppermint articles cover those herbs in detail. If you use essential oils, our lavender and dilution articles cover pregnancy cautions.

Breastfeeding: fenugreek and dong quai

Fenugreek is the best-known herb for milk supply, and NIH’s LactMed database updated its review in July 2026¹¹. Its verdict is cautious. Two pooled analyses disagree, and LactMed says the effect may be mostly psychological¹¹.

In one randomized, blinded trial of 176 mothers, those eating lactation cookies made no more milk than those eating ordinary store-bought chocolate chip cookies: about 5.5 versus 5.8 milliliters an hour¹¹. In a U.S. survey, 45% of 85 fenugreek users reported a side effect¹¹.

Reported problems include diarrhea, nausea and gas in mothers, gassy babies and allergic reactions¹¹. Cross-reactions with peanuts, chickpeas and other legumes are possible¹¹. Doses for milk supply usually run 1 to 6 grams a day. At roughly 25 grams or more, fenugreek may lower blood sugar, so mothers with diabetes should be careful with large doses, and the herb can interact with the blood thinner warfarin to cause bleeding¹¹.

Above all, LactMed says a milk-boosting herb is no substitute for working out, with expert help, what is holding supply back¹¹. MotherSafe likewise suggests seeing a breastfeeding expert first².

Dong quai, a “women’s herb” in Chinese medicine and common in Asian postpartum mixtures, has no recognized use in breastfeeding¹². LactMed found no data on how much reaches milk, flags bleeding risk with warfarin and similar drugs, and says it is best avoided while nursing¹². We found no reliable pregnancy safety data for it in the sources we reviewed.

Blue cohosh doesn’t belong in nursing either. LactMed warns of serious heart and digestive toxicity, including in newborns whose mothers took it to start labor, and says most sources strongly advise against it while breastfeeding¹⁴.

Your pregnancy herb check

Respect for tradition and respect for a baby’s development can point the same way: start with the herbs whose track record you can see. This table is our summary of the sources above, not a substitute for your clinician.

Herb	What’s known	Typical expert advice
Pennyroyal (oil or tea)	Deaths from liver and organ failure; infant harm from tea45	Avoid in pregnancy and breastfeeding5
Blue cohosh	Newborn heart, breathing and stroke case reports; no proof it works614	Only under medical supervision, if at all; avoid while nursing614
Licorice root (large amounts)	Linked to lower test scores and earlier puberty in children7	Finland: not recommended in pregnancy7
Raspberry leaf	One trial: no benefit, no clear harm; UK panel: risk low but uncertain9	Can’t be specifically recommended2
Echinacea	Small studies reassuring; alcohol in tinctures3	Use only if your provider advises it3
Herbal teas, in moderation	Limited safety data2	Considered safe in moderation; read blends for licorice28
Fenugreek (breastfeeding)	Mixed evidence; frequent side effects11	See a breastfeeding expert first211
Dong quai (breastfeeding)	No milk data; bleeding risk with blood thinners12	Best avoided while nursing12

What the evidence shows

Claim	Evidence rating	What it rests on
Pennyroyal safely brings on a period or ends a pregnancy	Evidence says no, or unsafe	Deaths and liver failure; no evidence it works45
Blue cohosh safely starts labor	Evidence says no, or unsafe	Serious newborn case reports; efficacy rests on opinion6
Heavy licorice is a harmless treat in pregnancy	Evidence says no, or unsafe	Observational Finnish data; cause not proven7
Raspberry leaf shortens or eases labor	Not enough evidence	One controlled trial found no difference; other studies open to bias910
Echinacea is safe in pregnancy	Not enough evidence	Small studies reassuring, but limited3
Fenugreek increases milk supply	Promising but early, at best	Mixed trials; a blinded trial found no effect11

Questions readers ask

The bottom line

A small number of herbs have earned real warnings in pregnancy: pennyroyal above all, blue cohosh for labor, and large amounts of licorice. Most other herbs sit in a gray zone, with thin data. Raspberry leaf and fenugreek have been tested, and neither has clearly done what its reputation promises.

Choosing natural care during pregnancy and nursing is a values decision, and it deserves good information. Bring your full list to your OB or midwife, ask whether each herb is “known risky” or “simply untested,” and use MotherToBaby and LactMed when you need a second expert.

Related reading

• Ginger earns its place for nausea, while its other promises are smaller
• How to judge a cup of herbal tea, which is gentle but not automatically harmless
• What happens when you don’t tell your doctor about supplements
• Chamomile eases worry a little, and its skin and colic claims rest on less
• About 220 pounds of lavender make a pound of oil, which is why dilution matters

Sources

1. Im HB, Hwang JH, Choi D, Choi SJ, Han D. “Patient-physician communication on herbal medicine use during pregnancy: a systematic review and meta-analysis.” BMJ Global Health, 2024; e013412 (abstract via OUCI index). pubmed.ncbi.nlm.nih.gov
2. MotherSafe (NSW Medications in Pregnancy and Breastfeeding Service), Royal Hospital for Women. “Herbal Medicines in Pregnancy and Breastfeeding.” April 2020. seslhd.health.nsw.gov.au
3. MotherToBaby, Organization of Teratology Information Specialists. “Echinacea” fact sheet. March 1, 2025. mothertobaby.org
4. National Institute of Diabetes and Digestive and Kidney Diseases. “Pennyroyal Oil.” LiverTox, NCBI Bookshelf, last updated March 28, 2020. ncbi.nlm.nih.gov
5. Memorial Sloan Kettering Cancer Center. “Pennyroyal.” About Herbs, last updated January 12, 2022. mskcc.org
6. Dugoua JJ, Perri D, Seely D, Mills E, Koren G. “Safety and efficacy of blue cohosh (Caulophyllum thalictroides) during pregnancy and lactation.” Canadian Journal of Clinical Pharmacology, 2008;15(1):e66-e73. e-lactancia.org
7. University of Helsinki. News release on Räikkönen K, et al., American Journal of Epidemiology, 2017, reprinted as “Not So Sweet: Liquorice Consumption Has Harmful Effects on Fetal Development.” Neuroscience News, February 3, 2017. neurosciencenews.com
8. Bazilchuk N. “Licorice can be harmful to the developing foetus.” ScienceNordic, February 10, 2017. sciencenordic.com
9. UK Committee on Toxicity (COT). “Statement on the potential health effects of raspberry leaf tea in the maternal diet.” COT Statement 2024/06, November 2024 (includes summaries of Simpson M, et al., 2001 and Parsons M, et al., 1999).
10. Bowman RL, Taylor J, Davis DL. “Raspberry leaf (Rubus idaeus) use in pregnancy: a prospective observational study.” BMC Complementary Medicine and Therapies, 2024;24:169. link.springer.com
11. National Library of Medicine. “Fenugreek.” Drugs and Lactation Database (LactMed), NCBI Bookshelf, revised July 15, 2026. ncbi.nlm.nih.gov
12. National Library of Medicine. “Dong Quai.” Drugs and Lactation Database (LactMed), NCBI Bookshelf, accessed October 2026. ncbi.nlm.nih.gov
13. America’s Poison Centers. Poison Help line, 1-800-222-1222. Poisonhelp.org, accessed October 2026. poisonhelp.org
14. National Library of Medicine. “Blue Cohosh.” Drugs and Lactation Database (LactMed), NCBI Bookshelf, revised December 15, 2024. ncbi.nlm.nih.gov