By Dónal P. O’Mathúna, PhD
Senior Lecturer in Ethics, Decision-Making & Evidence, School of Nursing and Human Sciences, Dublin City University, Ireland
Dr. O’Mathúna reports no financial relationships relevant to this field of study.
SYNOPSIS: A retrospective survey asked women shortly after delivering babies about their use of herbal remedies during their pregnancy. The answers were correlated with various pregnancy outcomes. The study unexpectedly identified higher risks from herbal remedy use on some outcomes.
SOURCE: Facchinetti F, et al. Herbal supplements in pregnancy: Unexpected results from a multicentre study. Hum Reprod 2012;27:3161-3167.
Numerous surveys in various countries have found that women tend to use herbal remedies more frequently than men. Use of herbs among pregnant women has been documented to range between 4% and 45%. However, the safety of using herbs during pregnancy is poorly understood.1 At the same time, some herbs and supplements are being marketed for pregnancy on the basis that they provide nutrients and are safer than conventional medications.
For these reasons, this study was conducted at three general hospitals in northeastern Italy. A total of 725 Italian women were randomly selected from all those giving birth, of which 700 agreed to be interviewed while at the hospitals within 3 days of delivery. During the interview, a pre-structured questionnaire was administered. The questionnaire was given within a face-to-face interview by a specially trained gynecologist to collect more complete data and address any questions the women might have had about the questionnaire.
The questionnaire collected data on the types and frequency of herbal remedy use, general socio-demographic details, and pregnancy-related outcomes. The main outcomes were preterm birth (delivery before the 37th week), low birth weight (infants weighing < 2500 g), and small for gestational age (≤ 10th percentile for sex and gestational age). Other outcomes measured were delivery before the 35th week, gestational age at birth, birth weight, and Apgar score at the fifth minute.
Among the 700 women interviewed, 297 (42%) reported using herbs at least once during their pregnancy. Among those taking herbs, 27 (10%) took them during the first trimester, 54 (18%) during the second, and 139 (47%) during the third. The length of time women consumed herbs during their pregnancy varied between 46.1% taking them for the entire pregnancy, 17.5% for 3 months, 31.6% for 1-2 months, and 4.7% for 1 week or occasionally. The first two categories were combined and called "regular users" for the purpose of analyzing the results.
The most frequently used herbs were almond oil applied topically (56.6%) and various herbs taken orally, including chamomile (35.7%), fennel (10.1%), valerian (3.4%), and echinacea (1.3%). The herbs were taken for relatively minor complaints such as skin stretch marks, anxiety, sleep disturbances, fluid retention, or constipation. Four women reported side effects, with three cases of skin reactions from continuous topical use of almond oil or aloe, and one case of constipation after regular consumption of a multiherb mixture.
Among the pregnancy-related outcomes, two of the three main outcomes were found to be significantly higher among regular users of herbs compared to non-users. The risk of low birth weight and the risk of giving birth before the 37th week were significantly higher (P = 0.031 and 0.049, respectively). Birth weight was lower (P = 0.038), but all other outcomes did not differ significantly. As topical almond oil and oral chamomile were the most frequently used herbs, further analyses were conducted on these. Regular almond oil users had a higher risk of preterm birth (odds ratio [OR] = 2.09; 95% confidence interval [CI], 1.07-4.08; P = 0.030) and regular consumers of chamomile had a higher, but non-significant, risk of low birthweight babies (OR = 2.1; 95% CI, 0.99-4.60; P = 0.052). Several confounding factors were investigated, with only smoking found to have a significant association with low birthweight.
The researchers noted that their adverse findings were unexpected and require further investigation. They have identified an association, not causation, which needs to be confirmed in further studies.
|Variable||Adjusted OR||95% CI|
|Topical almond oil||0.76||0.27-2.10|
> 40 years
≤ 8 years
Studies of herbal use by pregnant women in the United States have found rates ranging from 4-45%. The most recent study, reported in March 2013, found that 39% of women delivering at Boston Medical Center used herbal remedies during their pregnancies.1 This study did not ask about adverse effects. The most commonly used herbs in this survey were ginger and peppermint, both were used for morning sickness. The next most commonly mentioned herbs were chamomile, raspberry, ginseng, castor oil, evening primrose, and echinacea. The available evidence regarding the effectiveness of herbal remedies for nausea and vomiting in early pregnancy is limited and inconsistent.2
For this reason, concerns about any adverse effects of herbal remedies during pregnancy need to be considered carefully. The Italian study reported here took extensive efforts to ensure a high response rate (97%). The study’s findings highlight ways in which herbal remedy use may have unexpected effects. Massaging the oil into the abdomen may have mechanically stimulated the myometrium.
Alternatively, the authors identified studies in which almond oil was found to have high concentrations of vitamin E, vitamin C, oleic acids, and linoleic acids. Almond oil has been used as a carrier solvent for herbal remedies said to treat menstrual difficulties. In this way, the researchers speculated that some ingredients in the oil may have had unexpected effects on uterine contractions.
The study has some limitations. As a retrospective survey, accurate recall may have been an issue. It is also possible that some other confounding factor was involved that the researchers did not measure. Several outcomes were measured, with only two having significant associations. When several outcomes are measured, the risk of chance associations increases. In this regard, it is interesting to compare this study’s results with those of an earlier, similar study by the same research team. This study was carried out in two of the three hospitals and found that 27.8% of 392 Italian women used at least one herb during pregnancy.3 The two Italian studies found a similar range of herbs being used, although in the earlier one chamomile was the most popular (44%) and topical almond oil was much less popular (9.2%). Almond oil massage may grow in popularity as a recent report found that daily almond oil massage was more effective in preventing striae gravidarum during pregnancy than application of almond oil without massage or a control.4
The application of these results to U.S. women is challenging. Cultural differences regarding the use of herbs during pregnancy may exist. Also, the specific herbal products available may differ, both by location and date. A particularly problematic product may give rise to concerns in one place at one time and not be of concern elsewhere. As the authors themselves note, this study highlights the importance of not assuming that natural products are perfectly safe. One of the concerns raised by the Boston study was that while most women had their use of prenatal vitamins documented in their medical records, use of herbal remedies was not mentioned.1
Much more research is needed to understand the impact of herbal remedies during pregnancy. Neither the Italian nor the U.S. study examined fetal outcomes, which is another area in need of research. It is clear that pregnant women should be asked about the herbs they are using and these should be documented in case anything unexpected needs to be followed up at a later point. n