CRD summary: The authors concluded that ginger may be a safe and effective option for the treatment of nausea and vomiting in pregnancy, but further research is required to confirm these findings. The authors' cautious conclusions seem reasonable, although the evidence base was small, and the stated need for further research appears justified.

CRD commentary: The review question was clear in terms of the intervention, population and study designs. The literature search was not limited by language and some attempt was made to locate unpublished material, thereby reducing the potential for publication and language biases. The methodological procedures undertaken to select studies, assess quality and extract the data were likely to have minimised reviewer error or bias. The results data were not reported for individual studies, which meant that it was not possible to confirm the reported results. The authors highlighted a number of limitations in their discussion, including the short duration of treatment and generalisability to pregnant women worldwide. The authors' cautious conclusions seem reasonable, but the evidence base was small. The stated need for further research appears justified.