Herbal Product Use Common in Pregnancy, May Pose Risks to Fetus

From Medscape Medical News
Fran Lowry

December 30, 2009 — Use of herbal products during the period just before and during pregnancy is common among US women. Because so little is known about the effects of herbals on the developing fetus, however, healthcare providers should counsel their patients to err on the side of caution and avoid their use, according to an analysis published online December 28 in the American Journal of Obstetrics and Gynecology.

"Herbal use surrounding pregnancy raises particular concerns, because many herbals are marketed specifically for symptoms that occur commonly during pregnancy, such as nausea and vomiting," write Cheryl S. Broussard, PhD, from the Centers for Disease Control and Prevention in Atlanta, Georgia, and colleagues. "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."

In this study, the researchers sought to estimate the prevalence and patterns of herbal use among US women immediately before and during pregnancy.

They used data from the National Birth Defects Prevention Study, 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.

Their analysis included 4239 women who delivered infants without major birth defects between 1998 and 2004.

A computer-assisted telephone interview was used to collect data from mothers about exposures in the 3 months before pregnancy and throughout pregnancy to delivery. The women were asked: "Did you use any herbs or folk medicines to treat any medical conditions, to lose weight, or just to keep you healthy?"

The researchers found that 462 mothers (10.9%) reported use of an herbal product 3 months before or during pregnancy. During pregnancy, the overall prevalence was 9.4% and was highest during the first trimester (6.9%). A substantial proportion of women took herbal products during the second (5.1%) and third (5.2%) trimesters.

The use of herbal products increased with age, with a higher prevalence associated with age older than 30 years, and herbal use was also highest among women with more than a high school education and those with a household income of $20,000 or more per year.

The most commonly used herbals early in pregnancy were ginger, probably because it is believed to prevent nausea and vomiting, and ephedra, the authors report. Later in pregnancy, herbal teas and chamomile were most commonly used.

Other commonly used herbals were cranberry extract, raspberry leaf, mint or peppermint, and primrose oil.

Herbal Product Use in First Trimester Raises Safety Concerns

The fact that use of herbal products was greatest during the first trimester of pregnancy raises concerns about fetal safety because this is a critical period of fetal organ development, the authors write.

They note that the US Food and Drug Administration withdrew ephedra from the market in April 2004 because of concerns about cardiovascular effects including increased blood pressure and irregular heart rhythm in adults — effects that could have implications for the fetus.

A limitation of this analysis is that the mothers self-reported their exposure. Another is the variable time to interview, as one fifth of the mothers were interviewed 12 to 24 months after their estimated date of delivery. These might have led to exposure misclassification or lack of specificity in defining the mother's exposure because the interviews relied on women's recall of exposures up to 3 years in the past, the authors note.

Knowledge of the effects of herbals on the developing fetus is "remarkably limited," the authors write. In addition, it is difficult to ascertain the ingredients in herbal products with any degree of reliability because of the nature of the herbal product industry, which may label ingredients inaccurately or change the blend of their ingredients. Finally, despite their widespread use, many pregnant women who use herbals do not tell their physicians.

It is therefore critical that risks and relative safety of herbal products in pregnancy be studied and that more data on the fetal risks associated with these products be accumulated, the authors say.

In the meantime, healthcare providers should ask their patients about their use of herbals "in a routine and nonjudgmental fashion," and they should also counsel their patients 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," the authors conclude.

Dr. Broussard has disclosed no relevant financial relationships.

Am J Obstet Gynecol. Published online December 28, 2009.