Study designs of evaluations included in the review
For the evaluation of efficacy, only double-blind, randomised controlled trials (RCTs) were eligible for inclusion. For the evaluation of safety, RCTs, uncontrolled trials, case reports and observational studies were eligible for inclusion.
Specific interventions included in the review
Studies evaluating the oral administration of a monopreparation of ginger were eligible for inclusion. In the efficacy studies, dosages ranged from 500 to 1,500 mg per day and the duration of treatment ranged from 3 days to 3 weeks. The comparators included placebo and vitamin B6.
Participants included in the review
Studies of women suffering from pregnancy-related nausea and vomiting, such as morning sickness and hyperemesis gravidarum, were eligible for inclusion. Studies with healthy volunteers, and individuals suffering from motion sickness, post-operative nausea and vomiting, inflammation, and drug-induced nausea and vomiting was excluded. The period of gestation in the efficacy studies ranged from less than 12 weeks to less than 20 weeks.
Outcomes assessed in the review
Several different outcomes were assessed: the severity of and relief of nausea and vomiting, the duration and number of occurrences of nausea and vomiting, change in health status, and the occurrence of side-effects. The included efficacy studies assessed nausea and vomiting using 4- or 10-point scales, visual analogue scales, the Likert scale and the Rhodes Index.
How were decisions on the relevance of primary studies made?
All reviewers independently selected papers for inclusion in the review; any disagreements were resolved through discussion.