Ginger in many forms is taken by pregnant women, with the hopes of alleviating the nausea and vomiting of pregnancy. These forms range from ginger tea, cookies, crystals, and sugars to inhaled powder and capsules containing ginger, as well as fresh ginger.
In a recently published metaanalysis of studies on ginger's use as an antiemetic during pregnancy, the authors concluded that the herbal supplement may be safe and effective for managing the nausea and vomiting of pregnancy (NVP). They noted, however, that more observational studies and larger randomized trials were needed before a definitive statement on safety could be made (Obstet. Gynecol. 2005;105:849–56).
The metaanalysis included six double-blind, randomized controlled trials of almost 700 women and an observational study that my colleagues and I conducted on 187 women taking ginger. This is the first metaanalysis of studies on the use of ginger as an antiemetic during pregnancy. In the six randomized controlled trials, 500–1,500 mg daily of ginger were used for 3 days to 3 weeks in women who were at less than 20 weeks' gestation (Am. J. Obstet. Gynecol. 2003;189:1374–7).
In four trials, ginger was more effective than placebo in controlling symptoms of NVP, and in the two remaining trials, ginger was as effective as vitamin B6 although I would add that vitamin B6—when used alone—is effective mostly for mild cases of NVP.
No serious adverse effects or pregnancy-related problems were detected in the five studies that looked at safety. The outcomes evaluated in the randomized trials included prepartum hemorrhage, preeclampsia, preterm birth, congential abnormalities, major malformations, perinatal and neonatal death, birth weights, and gestational age.
In the prospective observational study, we looked primarily at fetal safety, comparing outcomes in 187 pregnant women who took ginger in the first trimester with another 187 women who during the first trimester took drugs known to be nonteratogenic. With one exception, we found no significant differences in adverse pregnancy outcomes between the two groups.
The exception was that there were significantly more infants with birth weights of less than 2,500 g in the comparison group (6.4%, vs 1.6% in the ginger group), even though there were eight pairs of twins in the ginger group. There were two major malformations in the comparison group, and three in the ginger group (a ventricular septal defect, right lung abnormality, and kidney abnormality). At age 2, the daughter of a mother who took 1,000 mg of ginger per day from weeks 11–20 of gestation, as well as doxylamine/vitamin B6 in the first trimester, was diagnosed with idiopathic central precocious puberty. This may be a random finding.
In a subgroup of 66 women, we evaluated the effectiveness of ginger by asking them to rank from 0 to 10 how well ginger controlled NVP, with 0 as no effect and 10 as a maximal effect. The mean score was 3.3, not a very strong effect. Moreover, when we considered the form of ginger used, only capsules containing ginger were associated with an effect significantly greater than zero.
Thus, our observational study put effectiveness against placebo into context: While it is helpful to show in randomized controlled trials that ginger has a better antiemetic effect than placebo, the effect is very mild. Needless to say, many pregnant women are much more comfortable taking a natural product than a medication because of the perception that natural products are safer. But they should be aware that these products are not necessarily as effective as medicinal products, which in the United States and Canada, include ondansetron and metoclopramide.
At Motherisk, we advise women who call about ginger that it is probably safe and may help ease mild NVP, but it is unlikely to help with moderate to severe NVP.
A precautionary note: Women should also be aware that since there are many formulations of ginger, the amount of ginger in a given form is almost never certain. This is because natural products are not regulated with the same scrutiny as drugs. At this point, more studies comparing ginger with placebo probably are not needed. What would make sense now is to compare the safety and effectiveness of ginger and drugs, such as ondansetron and doxylamine and vitamin B6, medicinal products that have been proved to be safe and effective for nausea and vomiting in pregnant women.