Herbal remedies in pregnancy: why natural does not mean safe for your baby

How herbs reach your baby

Many pregnant women assume that herbal remedies are safe because they are not pharmaceutical drugs. This assumption is physiologically incorrect. The active compounds in herbs, including alkaloids, flavonoids, and volatile oils, are small molecules. They cross the placenta and enter fetal circulation in the same way that many medications do.

The important difference is that the fetal liver, especially in the first trimester when organs are forming, does not have the enzymatic capacity to metabolise and neutralise these compounds at the same rate as an adult liver. What your liver handles efficiently may accumulate in the fetus at different concentrations. This does not mean every herb causes harm, but it does mean that caution is the right default rather than assuming safety.

A 2023 systematic review published in Pharmaceutical Biology, focusing on women in the Eastern Mediterranean and North Africa, found that between a quarter and half of pregnant women in the region use herbal remedies during pregnancy, and that most do not tell their doctors. A Saudi study published in Sultan Qaboos University Medical Journal in 2020 documented high rates of use in the Hail region. Reasons given include treating nausea and vomiting, strengthening the uterus for labour, and the belief that natural means safe.

Common kitchen herbs and their pregnancy concerns

Fenugreek is one of the most widely used herbs in Arab cooking and in traditional postpartum care. In the small quantities used in cooking, it is considered acceptable. However, when taken in medicinal doses as a supplement or concentrated infusion, fenugreek contains compounds that stimulate uterine contractions and may induce premature labour. Pregnant women are generally advised to avoid large doses, particularly in the first and third trimesters.

Cinnamon in small cooking quantities is acceptable. Some people take it as a concentrated infusion to control blood sugar or as a folk remedy. In large doses, cinnamon contains cinnamaldehyde, which has uterine stimulating properties. In the first trimester, when the embryo is still implanting and developing its earliest structures, this effect is a cause for concern.

Thyme in its usual culinary quantities as a spice is not a concern. But as a medicinal preparation, a strong infusion, or an essential oil, it contains thymol, which is classed as a uterine stimulant. Essential oils as a category deserve the most caution during pregnancy because their concentration is far higher than the equivalent spice. A few drops of thyme essential oil contain the same active compounds as many cups of dried herb.

Saffron and black seed: culturally important, questions remain

Saffron holds particular cultural significance across Arab societies, and there is a widespread folk belief that it improves the complexion of the unborn baby. A 2026 integrative review published in the Journal of Evidence-Based Integrative Medicine examined the available evidence and found that saffron in the medicinal doses used as a supplement stimulates the uterus and causes myometrial contractions. The few threads used occasionally in cooking are considered unlikely to cause harm. A daily concentrated saffron drink is a different matter.

Black seed in its culinary quantities is considered acceptable during pregnancy. Concentrated black seed oil or high medicinal doses falls into the same category as other uterine stimulating herbs. Animal studies have shown uterine stimulating effects at high doses, which is reason for caution particularly in the first trimester and late in pregnancy.

The honest answer to questions about both these herbs is that the clinical data from controlled trials on pregnant women is insufficient to declare complete safety at any dose. In the absence of that evidence, the prudent recommendation from most health authorities is caution: culinary use is unlikely to cause harm, but medicinal supplementation should be discussed with a doctor first.

Senna and herbal laxatives: a risk that is underestimated

Constipation is one of the most common complaints in pregnancy, and many women turn to senna and other herbal laxatives as a natural solution. Senna contains anthraquinone compounds that stimulate colonic motility, but they also cross the placenta and are excreted in breast milk. In pregnancy, stimulating the bowel with powerful laxatives risks transmitting that stimulating effect to the adjacent uterus.

Herbal laxatives that work by drawing water into the bowel or by strong bowel stimulation add the risk of dehydration in the mother. Reduced maternal blood volume affects placental blood flow and therefore fetal oxygen and nutrient delivery. The safer approach to constipation in pregnancy is increased dietary fibre and adequate fluid intake, for which there is good evidence of effectiveness. If medication is needed, lactulose and ispaghula husk are considered more acceptable options and worth discussing with a doctor.

The general principle in pregnancy is that anything that powerfully activates smooth muscle in the gut may activate smooth muscle in the uterus, because these tissues share some of the same receptor types. This is not a certainty in every case, but it is a rational basis for the caution recommended by obstetric guidelines worldwide.

Nausea in pregnancy: what actually helps and what to avoid

Pregnancy nausea in the first trimester has driven many women toward herbal solutions. Ginger is the most studied herb in this context, and several trials have shown it reduces nausea at modest doses and is generally considered acceptable in culinary quantities. However, ginger in high medicinal doses has been associated in some studies with effects on blood clotting, making caution appropriate close to the expected delivery date.

Peppermint and chamomile as light infusions are generally considered acceptable in moderate use. The essential oils extracted from them at high concentrations are entirely different substances. A single drop of essential oil of chamomile is equivalent in its active compound concentration to many cups of the tea, and some chamomile oils contain compounds with uterine stimulating properties at higher concentrations.

Green tea contains caffeine, and accumulating evidence links high caffeine intake in pregnancy to smaller birth weight and increased miscarriage risk. Total caffeine from all sources should remain below 200 mg per day in pregnancy according to World Health Organization guidance, and this includes coffee, tea, and caffeinated drinks. Several cups of green tea per day can approach or exceed this limit.

What uterotonic means and why it matters

A uterotonic agent is any substance that increases uterine contractility. In the final stages of labour, this is exactly what is needed to deliver the baby and reduce postpartum haemorrhage. But in the first trimester, when the embryo is implanting and the pregnancy is most vulnerable, uterine contractions are the primary threat to its continuation. A uterotonic compound used at this stage can cause miscarriage.

In the third trimester and the final weeks, the risk shifts to inducing labour before the baby has completed its lung and brain development. This is the concern behind traditional recipes used to prepare the womb for birth or to ease delivery. Some of these preparations are genuinely effective, and that is precisely the danger: they can trigger labour at a point when the baby may not be ready.

A comprehensive review published in the Journal of Ethnopharmacology in 2014 documenting plants with uterotonic properties around the world found that many such plants are used across cultures for purposes related to pregnancy and delivery. A large number of them work through receptors that are similar to or overlap with those activated by oxytocin, the hormone that drives labour naturally.

What to do if you have been taking an herb

The first and most important step is disclosure. Tell your doctor or midwife everything you take, including herbs, supplements, and traditional preparations. Many women hesitate to mention this, fearing judgement or worrying about embarrassing whoever recommended the herb. Your doctor does not judge your choices; they need the information to assess your situation accurately, particularly because some herbs interact with prescribed pregnancy medications.

If you are using an herb for a specific reason such as nausea, blood sugar control, or constipation, ask your doctor about a documented safe alternative. In most cases a dietary or medical approach exists that carries more established safety data than the herb you are using.

If you took an herb before you knew you were pregnant, do not be alarmed. Brief exposure to small amounts of most herbs in the earliest weeks of pregnancy is unlikely to cause definite harm. What matters is stopping now and mentioning it at your next antenatal appointment. Prolonged anxiety about something that has already passed does not help the baby.

Herbs and breastfeeding: a separate question

The postpartum period carries its own herbal traditions. In Arab culture, women are often encouraged to take fenugreek, dill, and aniseed to increase milk supply. These are in most cases considered safe for the mother in their usual forms and some have reasonable evidence for effectiveness in increasing milk production. However, the effect extends to the baby through the milk, and any mother who knows her infant has a health condition or allergy should mention it.

Herbs taken for medical purposes during breastfeeding need the same level of caution as during pregnancy. Some herbs reduce rather than increase milk supply, contrary to what some believe, including peppermint and sage in large quantities. Some can affect an infant's sleep pattern or digestive comfort. The principle of telling the doctor what you take applies equally in this period.

Why definitive answers are hard to find

The reason that safety data on herbs in pregnancy is often inconclusive is that controlled clinical trials in pregnant women are rare for understandable ethical reasons. Most of what is known comes from case reports, observational studies, and extrapolation from animal data. The absence of evidence is not evidence of safety. It means simply that the data does not exist.

This is why the precautionary principle applies. In the absence of robust evidence of safety, caution is the wiser choice for a pregnant woman. This does not mean rejecting everything natural; it means choosing what has an established safety record and avoiding what has not yet been demonstrated safe.

The World Health Organization has published monographs on widely used medicinal plants covering effectiveness and safety, and many of these explicitly note conditions in which use during pregnancy is not recommended. These resources are available and a doctor or pharmacist can consult them to answer specific questions about a herb you have been using.

Sources

• Bouqoufi A, Lahlou L, Ait El Hadj F et al: Prevalence, motivation, and associated factors of medicinal herbs consumption in pregnant women from Eastern Mediterranean Regional Office: a systematic review, Pharmaceutical biology, 2023
• Aljofan M, Alkhamaiseh S: Prevalence and Factors Influencing Use of Herbal Medicines During Pregnancy in Hail, Saudi Arabia: A cross-sectional study, Sultan Qaboos University medical journal, 2020
• Alshdefat A, Ayed A, Aqtam I et al: Saffron and Pregnancy: Cultural Practices, Beliefs, and Safety Evidence: An Integrative Review, Journal of evidence-based integrative medicine, 2026
• van Andel T, de Boer HJ, Barnes J et al: Medicinal plants used for menstrual disorders in Latin America, the Caribbean, sub-Saharan Africa, South and Southeast Asia and their uterine properties: a review, Journal of ethnopharmacology, 2014
• World Health Organization: WHO monographs on selected medicinal plants. WHO, Geneva, 1999
• Tiran D: Ginger to reduce nausea and vomiting during pregnancy: evidence of effectiveness is not the same as proof of safety, Complementary therapies in clinical practice, 2012