Herb-Drug Interactions During Pregnancy

According to a recent study, over 1 in 5 pregnant women are taking both prescription drugs and self-prescribed herbal supplements, many of which are known to pose a risk of interactions leading to adverse health outcomes. Because pharmaceuticals are prescribed by a care provider and herbal supplements are typically self-prescribed, the risk of interactions is significant without guidance from a professional who is knowledgeable in the risks posed by these interactions. During pregnancy, these risks become much more serious. Researchers sought to quantify the threat posed by herb-drug interactions in this cross-sectional study. These findings underscore the importance of seeking independent information about herbal product safety from a qualified professional.

The Study

Pregnancy, prescription medicines and the potential risk of herb-drug interactions: a cross-sectional survey.


Scottish researchers investigated the potential for herb-drug interactions due to self-prescribed botanical products and supplements by conducting a cross-sectional study. In this study, researchers not only looked for prevalence of supplement use, but also the risk level of the potential interactions among the pharmaceutical and natural products being taken by the pregnant participants. Multiple publications were produced from data collected during this study (Pallivalappila et.al., 2014; Pallivalapila et.al., 2015).

Measurement Instrument

The data for this study were collected from patients while they were visiting the hospital. Data covered use of prescription medications during pregnancy and use of herbal supplements during pregnancy. Researchers also collected demographic data, such as age and educational status, during the study, as well as data regarding the patients’ attitudes about using Complementary and Alternative Medicine (CAM) both overall and specifically during pregnancy. The survey was evaluated for face and content validity.

The Participants

This sample included 889 participants who were either visiting a provider during the middle of their pregnancies (18-21 weeks) or within the immediate postpartum period during the data-collection phase of the study, which occurred from March to August of 2012. All of the patients surveyed came from the same hospital ward and they were recruited for participation during their pregnancy or birth related hospital visits.


The study found that women who were over the age of 35 and had a university education were the most likely to self-prescribe herbal supplements. This is consistent with multiple other studies, where there is a positive relationship between age and educational status.

Just over 20% of the patients in the study used both pharmaceutical prescriptions and herbal supplements during their pregnancies. Many of these are relatively safe supplements such as ginger, chamomile, and cranberry. Prescription drugs ranged from antidepressants to thyroid medications to those used to treat nausea.

A total of 34 herb-drug interactions were found by the researchers during the analysis. Only one of the interactions was classified as minor. One was classified as a potential serious risk and the others were all classified as moderate risks. Many of the moderate risks identified were due to additive effects, where the herb and the drug work together synergistically to produce stronger effects. These can produce an overdose of the drug in the body, resulting in an increased risk of bleeding, hypoglycemia, hypotension, CNS depression, and other moderate health concerns.

While many herb-drug interactions involve additive effects where the total dose or concentration in the body is increased, some interactions result in a reduction of effects of prescription drugs. In these situations, the addition of an herbal supplement to the routine produces a reduced dose of a pharmaceutical drug, and its associated consequences.

Practically, this means that over 1 in 5 women in this study were consuming herbal supplements during their pregnancies which pose a moderate health risk to themselves and their babies. This risk is frequently associated with the self-prescription of an herb or essential oil without seeking education about the risks and benefits of a botanical from a qualified professional.


So what does all of this mean? A cross-sectional study is the research equivalent of a quick snapshot. It provides a lot of detail about a specific population at a specific moment in time. In this case, it reveals that there is a significant risk of herb-drug interactions among pregnant women.

Cross-sectional studies are designed to identify relationships, not establish causation, so the study did not include analysis of the total interactions that did occur as a result of the intake of herbal supplements without professional guidance. Other research methodology would be better suited for answering that follow-up question.

It is important to note that herbal supplements and pharmaceuticals can be used safely during pregnancy. However, identifying how to select and use herbal supplements while under the care of a health professional for another condition requires consulting with a professional who is thoroughly trained to provide education in the safe use of botanicals.

Study Review: 

McLay, J. S., Izzati, N., Pallivalapila, A. R., Shetty, A., Pande, B., Rore, C., … & Stewart, D. (2017). Pregnancy, prescription medicines and the potential risk of herb-drug interactions: a cross-sectional survey. BMC complementary and alternative medicine17(1), 543.

Additional References: 

Pallivalappila, A. R., Stewart, D., Shetty, A., Pande, B., Singh, R., & Mclay, J. S. (2014). Complementary and alternative medicine use during early pregnancy. European Journal of Obstetrics & Gynecology and Reproductive Biology181, 251-255.

Pallivalapila, A. R., Stewart, D., Shetty, A., Pande, B., Singh, R., & McLay, J. S. (2015). Use of complementary and alternative medicines during the third trimester. Obstetrics & Gynecology125(1), 204-211.


Have more questions? The entire study article is available via open access.

Meet Dr Hawkins

Dr. Hawkins brings 20 years of expertise in the integrative health field to her role as Executive Director of the Franklin School of Integrative Health Sciences and the leader of our clinical research team.

She holds a Bachelor’s Degree in Environmental Health from Union Institute and University, a Master’s Degree in Health Education & Promotion from the University of Alabama, a post-graduate certificate in epidemiology from the London School of Hygiene and Tropical Medicine, a PhD in Health Research from Middle Tennessee State University, and is completing the post-doctoral Global Scholars Research Training Program at Harvard Medical School. She also holds certifications in numerous natural health fields including aromatherapy, aromatic medicine, herbalism, childbirth education, and labor support.