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Epidemic Intelligence Service, Office of Workforce and Career Development, Centers for Disease Control and Prevention, Atlanta, GADivision of Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, GA
We estimated the prevalence and patterns of herbal use among US women before and during pregnancy.
The National Birth Defects Prevention Study is an ongoing, population-based, case-control study. This analysis included 4239 women from 10 centers in the United States who delivered infants without major birth defects from 1998–2004.
The prevalence of reported herbal use 3 months before or during pregnancy was 10.9%. During pregnancy, prevalence was 9.4% and was highest in the first trimester. Higher prevalence was associated with age greater than 30 years and education greater than 12 years. Use varied considerably by state (5–17%). Ginger and ephedra were the most commonly reported products early in pregnancy; teas and chamomile were most commonly reported throughout pregnancy.
Potentially 395,000 US births annually involve antenatal exposure to herbal products. Health care providers should inquire routinely about herbal use and educate patients about what little is known regarding risks of these products.
There is a lack of published US data on the frequency of herbal use among women of childbearing age in general; published estimates specifically during pregnancy range from 4.1–45.2%, but these were based on sample sizes of only 150–734 women.
Under the Dietary Supplement Health and Education Act of 1994, the responsibility for ensuring safety before marketing rests with the manufacturers, and the US Food and Drug Administration (FDA) can take regulatory action only if it can prove that a product is unsafe once it reaches the market.
More importantly, our ignorance of the potential harm to the pregnant woman is complicated by our even greater ignorance of the potential effects on fetal safety.
Because little is known about the extent of herbal use among pregnant women, we estimated the prevalence and pattern of use among women immediately before and during pregnancy.
Materials and Methods
To estimate the prevalence of herbal use among a population-based sample of women who delivered liveborn infants with no major birth defects, we used data from the National Birth Defects Prevention Study (NBDPS). The NBDPS is an ongoing, population-based, case-control study involving case infants with major structural birth defects and control infants without such defects, conducted in 10 centers across the United States: Arkansas, California, Georgia, Iowa, Massachusetts, New Jersey, New York, North Carolina, Texas, and Utah. Each center defined a study region with between 35,000–75,000 births per year, which in some cases was statewide and in other cases was a region in a state.
The control infants are a random sample of live births drawn from the same source population as the case infants, with the selection occurring from either birth certificates or hospital birth records. About 900 mothers of control infants are interviewed each year, and only control mothers were included in this analysis. The study was approved by the institutional review boards of the Centers for Disease Control and Prevention and all participating study centers.
The study uses a computer-assisted telephone interview to collect data from mothers about exposures in the 3 months before pregnancy and throughout pregnancy, the latter defined as the time period from conception (ie, 2 weeks after the last menstrual period) to delivery. Each month was a 30-day period, and, for this analysis, trimesters were defined as 3-month periods (first trimester: pregnancy months 1–3; second trimester: pregnancy months 4–6; and third trimester: pregnancy months 7–9, which some mothers did not reach, because they delivered in the second trimester). Interviews are conducted from 6 weeks to 2 years after the estimated date of delivery (EDD), with a mean and median time to interview for control mothers of 8.9 and 7.7 months, respectively, after the EDD.
The questionnaire item related to herbal use stated: “Did you use any herbs or folk medicines to treat any medical conditions, to lose weight, or just to keep you healthy?” This question covered the time period from 3 months before pregnancy to the date of the child's birth. Analysis was restricted to control mothers who had answered this particular question.
From among the responses provided by study participants, herbal products in this analysis were defined as “products containing a plant, plant part, or plant extract (excluding topicals)” (eg, black cohosh, chamomile oil, ephedra, and Ginkgo biloba). Products were classified using the Slone Drug Dictionary from Boston University's Slone Epidemiology Center,
which links the reported substances to their active ingredients. We included herbal teas that were reported in response to the specific herbal question or in any other section of the questionnaire.
When herbal exposure was reported in an alternate section of the questionnaire (eg, vitamin use section or maternal illness section), the reason for use was attributed to that topic. We excluded exposure to single herbals in mainly vitamin-dominated multivitamin supplements.
The herbal question was added in mid-2000; therefore, for this analysis, we included only women interviewed after this time, which corresponds to participants with EDDs between mid-1998 and the end of 2004 (4239/5958 total controls). The participation rate in the maternal interview was approximately 69% among control mothers for this time period.
STATA 8 software (Stata Corp, College Station, TX) was used for all analyses. We cross-tabulated herbal use with each sociodemographic characteristic of interest to determine the prevalence associated with each of these factors. The 3 months prior to pregnancy and the 3 trimesters of pregnancy were each considered a distinct “period” for purposes of this analysis, and prevalence of herbal use was calculated for each of the 4 periods. Percentages of mothers taking each herbal product were tabulated and ranked to determine the most commonly reported herbals.
Overall, 462 (10.9%) of the 4239 control mothers reported use of any herbal product in the 3 months before pregnancy or during pregnancy. The prevalence of herbal use by state varied considerably, with the lowest use in Iowa and North Carolina (5.4% and 6.1%, respectively) and the highest in Utah (16.5%) (Table 1). Use increased with age and also was greatest among women with more than a high school education and among women with a household income of $20,000 or more per year. Hispanics reported the highest prevalence of herbal use of all racial or ethnic groups studied.
TABLE 1Sociodemographic characteristics of control mothers by reported herbal use 3 months before and during pregnancy, 1998–2004
In the 3 months before pregnancy, the overall prevalence of herbal use was 5.7%. Only 65 mothers reported herbal exposure limited to the 3 months before pregnancy (ie, none were exposed during pregnancy); therefore, the overall prevalence of herbal use anytime during pregnancy was 9.4%.
During pregnancy, the prevalence was highest (6.9%) during the first trimester, but a substantial proportion of women took herbals during the latter trimesters as well (5.1% and 5.2% during the second and third trimesters, respectively); 275 (6.5%) mothers were exposed during more than 1 of the 4 periods, and 87 (2.1%) mothers were exposed in all 4 periods.
Timing of pregnancy recognition was available for all but 2 participants included in the analysis. Of these 4237 pregnancies, 52% were recognized by the mother during the first month, 37% during the second month, and 12% during the third month or beyond. Herbal use was significantly higher after pregnancy recognition (7.6% vs 6.1%; P = .003).
Among reported products, the most common herbals (each taken by <3% of mothers) were herbal teas, ephedra and ephedra-containing products (which also tended to include ginger, ginseng, or both), chamomile, echinacea, and ginger (Table 2). The other common products (reported by <0.5% of mothers) were cranberry extract, raspberry leaf, mint or peppermint, and primrose oil. A total of 33 of 119 herbal tea users also took another type of herbal product. Excluding the 86 women who used herbal teas only, the prevalence of all other herbal products used 3 months before or during pregnancy was 8.9%.
TABLE 2Top reported herbals used in the 3 months before and during pregnancy among control mothers, 1998–2004
Distribution of use of these most common products differed somewhat by trimester. As shown in Table 2, ginger was used predominantly during the first trimester, likely because of its claim to prevent nausea and vomiting during pregnancy. Ephedra was used both before pregnancy and during the first trimester of pregnancy (but not later in pregnancy); in contrast, herbal teas and chamomile were used throughout all 4 periods of pregnancy.
Although there appeared to be no substantial differences in the use of herbal teas, echinacea, or ginger by year of EDD (Figure), the prevalence of ephedra use declined substantially from 2002–2004, and chamomile use was reported more commonly by women with EDDs in the years 1998–2000.
Reported reasons for herbal use often were nonspecific, because they generally were attributed to the topic section of the questionnaire in which the herbal was reported. The most common reasons given for use, corresponding to topic areas in the interview, were as remedies or vitamins, and for respiratory conditions, morning sickness, and urinary tract infections. Of note, a considerable proportion (approximately 40% of the multiple-component products or 9% of all products) of the herbals had intended uses that included weight loss or body enhancement.
If we assume that our control mothers were representative of the 4.2 million births each year in the United States,
our findings project that 9.4%, or an estimated 395,000 such births, will involve antenatal exposure to at least 1 herbal product. Furthermore, the fact that use of herbal products was greatest during the first trimester raises concerns about fetal safety, because this is a critical period of fetal organ development.
(which could have implications for fetal risk); our survey documented that use declined subsequent to that withdrawal, but even with that decline, we estimated that there were 21,000–71,400 ephedra-exposed births per year over the course of the study period.
Slone Survey data restricted to women of childbearing age (18–44 years) found an approximate 10% prevalence of herbal use during the period 1998–2000 and about 15% use during the period 2001–2002.
This study was subject to several limitations. The self-reported exposure assessment, combined with the variable time to interview, might have led to exposure misclassification or a lack of specificity in defining the mother's herbal exposure, particularly because the herbal interview question was open ended. Because one-fifth of control mothers were interviewed 12–24 months after the EDD, these interviews relied on women's recall of exposures up to 3 years in the past.
There has thus far been no consensus on how best to ascertain herbal use in population surveys. In the NBDPS,
and it is reasonable to extrapolate this observation to herbals.
Visual aids have been particularly helpful, specifically for identification of herbals. Because no pictures or examples of herbals were provided in our study, it is possible that herbal use might have been overreported or underreported.
Furthermore, unlike prescription and over-the-counter medications, the ingredients in herbal products cannot reliably be predicted from the user's description of the product or even brand name because, due to the nature of the herbal product industry, proprietary blends can change, and labeled ingredients might be inaccurate.
Our estimates are conservative in that we excluded from our definition of herbals those multivitamin products that might contain a single herbal component.
A previous analysis comparing demographic and health factors of NBDPS control infants with those from natality data of target populations found the control participants to be generally representative of their base populations, particularly in terms of maternal and paternal age, previous live births, maternal smoking, and maternal diabetes.
This study also showed that the extent to which these controls were representative of the general population might be affected by the selection method, which differed by study center (hospital-based or birth certificate-based control selection).
In conclusion, we found that use of herbal products during the period just before and during pregnancy was relatively common among US women. Because of remarkably limited knowledge regarding the effects of herbals on the developing fetus, it is critical that we focus attention on the study of the risks and relative safety of herbal products in pregnancy. As more data accumulate, the NBDPS will attempt to evaluate the fetal risks and safety of herbal products taken by pregnant women, including the effects of specific herbal products on selected birth defects and interactions between herbals and over-the-counter and prescription medications.
In the meantime, health care providers should recognize that, despite the widespread use of herbal products by women of childbearing age, many herbal users do not disclose their use to a medical professional.
Providers should therefore attempt, in a routine and nonjudgmental fashion, to query patients about their use of herbals, and to counsel them that the fact that a substance is natural does not necessarily mean that it is safe for the fetus.
Providers also should inform patients that it would be prudent to err on the side of caution regarding use of these products during and surrounding pregnancy, because little is known about their potential risks.
Coding of drug information in the NBDPS used the Slone Drug Dictionary, under license from the Slone Epidemiology Center at Boston University, Boston, MA. We wish to thank the study participants, interviewers, and collaborators at all of the Centers for Birth Defects Research and Prevention: University of Arkansas for Medical Sciences, Little Rock, AK (Charlotte Hobbs, MD; U50/CCU613236); California March of Dimes, Oakland, CA (Gary Shaw, DrPH; U50/CCU913241); University of Iowa, Iowa City, IA (Paul Romitti, PhD; U50/CCU713238); Massachusetts Department of Public Health, Boston, MA (Marlene Anderka, PhD; U50/CCU113247); New York State Department of Health, Albany, NY (Charlotte Druschel, MD; U50/CCU223184); University of North Carolina School of Public Health, Chapel Hill, NC (Andrew Olshan, PhD; Robert Meyer, PhD; U50/CCU422096); Texas Department of State Health Services, Austin, TX (Mark Canfield, PhD; Peter Langlois, PhD; U50/CCU613232); Utah Department of Health, Salt Lake City, UT (Marcia Feldkamp, PhD, PA, MSPH; U50/CCU822097).
Factors associated with herb and dietary supplement use by young adults in the United States.
This study was supported in part by cooperative agreements under Program Announcement 02081 from the Centers for Disease Control and Prevention to the centers participating in the National Birth Defects Prevention Study, listed in the Acknowledgments section of the full-length article at www.AJOG.org.
The findings are conclusions in this article are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
Cite this article as: Broussard CS, Louik C, Honein MA, et al. Herbal use before and during pregnancy. Am J Obstet Gynecol 2010;202:443.e1-6.