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Randomised controlled trial
Ginger reduces severity of nausea in early pregnancy compared with vitamin B6, and the two treatments are similarly effective for reducing number of vomiting episodes
  1. Caroline Smith
  1. Correspondence to Caroline Smith
    Centre for Complementary Medicine Research, University of Western Sydney, Locked Bag 1797, Penrith South DC, NSW 1797, Australia; caroline.smith{at}uws.edu.au

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Nausea and vomiting are experienced by up to 85% of women during early pregnancy.1 Antiemetics are available for the management of these symptoms, but many do not bring satisfactory relief to all women,2 and there are concerns about potential teratogenic effects during the critical early stage of pregnancy. Consequently, many women look to other treatments to help manage their symptoms. Ginger has long been used to treat health complaints such as nausea. It is on the US Food and Drug Administration's3 list of safe herbal preparations and is listed in German and European monographs as being indicated for nausea. The effectiveness of ginger in treating nausea in pregnancy has been evaluated in a number of randomised controlled trials (RCTs) and summarised in a systematic review.4 In this review the authors concluded that ginger may be an effective treatment for the management of nausea but that further studies are needed.4

Ensiyeh and colleagues contribute to the small body of evidence comparing the effectiveness of ginger with that of vitamin B6. In this study 70 pregnant women with nausea were randomised to receive 1 g/day of ginger or 40 mg/day of vitamin B6. Treatment was administered over 4 days, with nausea outcomes collected 1 week later and pregnancy outcomes collected at delivery. The authors reported a reduction in nausea from baseline for women taking ginger compared with vitamin B6 (p<0.024). There was no difference in vomiting or in pregnancy outcomes between groups.

Insufficient reporting may have led to methodological biases in this study. The appropriateness of vitamin B6 as a control or comparator is questioned in the literature because there is insufficient evidence of its effectiveness. In this study the rationale for the vitamin B6 dose chosen was not reported, and 40 mg/day may have been suboptimal. Selection bias cannot be excluded. No details were given about the method of concealment of the randomisation schedule. Although the authors reported no differences between groups at randomisation there appears to have been an imbalance in parity, with a higher proportion of nulliparous women allocated to the ginger group. It would have been appropriate to adjust for parity in the analysis of the primary and secondary end points. No details were reported on blinding. Subjects were not masked as to whether they were being given vitamin B6 or ginger, and it is unclear whether the data analyst and other personnel involved with the study, including administration of the intervention and collection of secondary outcome data, were blinded to group allocation. Compliance was checked but not reported.

Gagnier and colleagues have made recommendations for reporting RCTs of herbal interventions to help assess their validity.5 Gaps in this study in the reporting of the results for ginger in terms of characterisation and quality testing prevent a complete assessment. Overall, it is unclear whether ginger was associated with a reduction in nausea or whether the results were influenced by bias and suboptimal doses. The strengths of the study relate to women not taking additional medication, and symptoms were measured three times a day.

Although the results regarding the effectiveness and safety of ginger from this study are positive, conclusions cannot be made regarding clinical practice. Overall, the evidence from a systematic review and the results from this study are suggestive of a benefit; however, further research should focus on observational studies characterising ginger, and placebo-controlled trials with improved reporting are required.

Many women have access to ginger over the counter and will choose to self-administer with or without advice from their health practitioner. If women seek advice on the use of ginger, health professionals may need to consider the evidence, potential drug–ginger interactions and the beliefs of the individual. Consultations with herbalists specialising in pregnancy should also be considered.

References

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Footnotes

  • Competing interests None.

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