Natural herbal supplements are a growing market and have become many people's 'go to' for everything from weight-loss to treating various ailments and maintaining overall health. Often marketed as ‘herbal medicines’, herbs, herbal preparations and finished herbal products contain parts of plants and/or plant materials as their active ingredients.
These natural herbs, pills and powders that reportedly harness nature's healing abilities and benefits are often regarded as a logical alternative to synthetic man-made concoctions. They don’t require a doctor's visit, and are available over-the-counter making them cost effective, easily accessible and convenient.
The problem, however, is that the general consensus among herbal users, and society at large for that matter, is that ‘natural’ means ‘safe’. This also mistakenly translates as ‘safe to use during pregnancy’.
While there is a growing body of evidence that some natural supplements are effective when treating certain health issues, and have solid evidence based profiles, there is, however, still always the possibility of various adverse side effects. In addition, the potential for herb contamination, toxicity, over-dosage and most commonly, interactions with other herbs or medications is also a great concern1.
Research into the effects of herbal supplements doesn’t always come naturally
There are hundreds of herbs with reportedly medicinal properties. The problem, however, is that research into the direct cause and effect relationships between many of these herbal products and their effects on human health is often lacking. As with most medications, this is even more pronounced when it comes to use in pregnancy.
What recent studies on herbal supplement use in pregnancy show
A recently published review of 74 published studies indicates that certain natural supplements could potentially be linked to an increased risk of complications in pregnancy, including pre-term birth and c-section delivery2.
The supplements researched in the various studies included the following:
- Almond oil: Research showed that women who applied almond oil to their skin during the third trimester of pregnancy were twice as likely as other women to give birth prematurely.
- Liquorice / Licorice: A common natural remedy for gastrointestinal issues and heartburn during pregnancy, studies on the effects of liquorice have found that women who consumed liquorice candy throughout pregnancy were at higher risk of delivering prematurely.
- Raspberry leaf: A popular herbal supplement thought to induce and shorten labour was linked to a 3.5 times higher need for c-section delivery in women who took it (although this a common complication in all labour-inducing techniques).
- Mwanaphepo: Studies on this African herb that is used to induce labour associated a higher risk of c-section delivery, other delivery issues and newborn death with its use.
Head researcher and co-author of the recent study, Dr James McLay of Royal Aberdeen Children’s Hospital in Scotland, is quick to point out that these studies do not provide conclusive evidence that the supplements studied were to directly to blame for the adverse outcomes. Instead, he emphasises that the review of evidence highlights the fact that studies on the use of herbal products in pregnancy to date have either been too small or not designed well enough to provide any conclusive evidence regarding the efficacy and safety of these supplements either way.
When asked to comment on the findings, Dr Anthony Scialli, an independent clinical professor of obstetrics and gynaecology at the George Washing University School of medicine, echoed Dr McLays sentiments, noting that underlying health issues observed in the studies could also have been to blame for the adverse pregnancy outcomes.
He added that certain herbal products like ginger for morning sickness had been studied far more widely than some others and was generally considered a safe and effective way to treat morning sickness symptoms. Nevertheless, ginger, like many other herbs prescribed for various pregnancy-related symptoms and stimulating breast milk production were still associated with some negative side effects. These may include:
- Chamomile: Allergic reaction, skin reactions (contact dermatitis), vomiting when consumed in large amounts.
- Cranberry: Diarrhoea
- Fenugreek (promoted as a breast milk production stimulant): Headaches and skin reactions
- Ginger: Dry mouth, headache and heartburn
- Peppermint: Allergies. Peppermint oil has been linked to the relaxation of the uterus and should therefore be avoided in pregnancy.
- Raspberry leaf: Headache, nausea, dizziness and changes in bowel function
- Valerian: Dry mouth, headache, gastrointestinal upset, anxiety, heart disturbances, excitability, insomnia.
Scialli also emphasised that not enough was known about all herbal products and that the ‘naturalness’ of a product or supplement did not automatically confer safety or danger either way. Individual supplements must be evaluated on a case-by-case basis and further studies to determine the potential benefits and adverse effects for each individual herbal supplement are required.
What this means for pregnant women
Herbal products and supplements contain chemicals that can have profound effects on the body and interact with other supplements and/or medications. The glaring lack of evidence regarding the efficacy and safety of these types of products is a very real problem particularly due to the fact that, depending on the country being examined, anywhere between 10% and three quarters of pregnant women take some form of herbal product to alleviate unwanted symptoms or as dietary supplements.
Until conclusive evidence is provided on the safety and efficacy of the various herbal products, pregnant women should be as cautious about these as they are conventional medications both during pregnancy and while breastfeeding.
If you are pregnant and unsure of whether a particular herbal supplement is safe to take or not, always consult your doctor or gynaecologist before taking it. Also ensure that you disclose any other supplements, vitamins, minerals or medications (whether over-the-counter or prescribed) that you may be taking. When it comes to your baby’s health and life, you can never be too careful.
1. Welz A, Emberger-Klein A, Menrad K. Why people use herbal medicine: insights from a focus-group study in Germany. BMC Complement Altern Med. 2018;18(1). doi:10.1186/s12906-018-2160-6
2. Muñoz Balbontín Y, Stewart D, Shetty A, Fitton C, McLay J. Herbal Medicinal Product Use During Pregnancy and the Postnatal Period. Obstetrics & Gynecology. 2019:1. doi:10.1097/aog.0000000000003217