TABLE 3.

Results summary of the included meta-analyses.

Author year	Method (fixed or random)	Effect estimate vs. placebo	Effect estimate vs. conventional treatments	Summary of results
Tan et al. [20], 2023	Random-effects model	NVP effective rate: RR: 1.68; (1.09, 2.57); P = 0.0018; I2 = 76.4% Nausea score: WMD: –1.21 (–2.34, –0.08); P = 0.036; I2 = 66.0% Vomiting score: WMD: 0.05 (–0.23, 0.32); P = 0.743; I2 = 0%	NVP score: WMD: := –0.52 (–0.79, –0.24); P ≤ 0.001; I2 = 0% (included metoclopramide) Vomiting score: SMD: 0.30 (–0.12, 0.73); P = 0.160; I2 = 51.1%	Ginger had a higher effective rate and improved nausea symptoms compared with placebo, but vomiting was not statistically significant. Ginger was more effective than vitamin B6 or metoclopramide on NVP score across 2 trials but had no effect on vomiting compared with vitamin B6.
Gaur et al. [26], 2022	Random-effects model	n/a	NVP overall: SMD: 0.36 (–0.21, 0.60); P = 0.02; I2 = 17% Nausea score: SMD: –0.15 (–0.28, 0.05); P = 0.87; I2 = 50.0% Vomiting score: SMD: –0.05 (–0.11, 0.21); P = 0.57; I2 = 0%	Both vitamin B6 and ginger treatment improved NVP symptoms overall across treatment duration in 2 studies; however, vitamin B6 may be more effective because of a greater reduction in NVP scores overall in the MA. There was no difference in nausea or vomiting scores between vitamin B6 and ginger.
Hu et al. [27], 2020	Random-effects and fixed-effects models	Fixed-effects NVP improvement ratio: OR: 7.475 (4.133, 13.520); P < 0.001; I2 = 30.1% Fixed-effects nausea score: SMD: 0.821 (0.585, 1.056); P < 0.001; I2 = 38.9% Random-effects vomiting score: SMD: 0.549 (0.585, –0.268); P = 0.188; I2 = 91.4%	Random-effects NVP: pooled OR: 1.239 (0.495, 3.102); P = 0.647; I2 = 57.3% Random-effects nausea score: SMD: 0.199 (–0.102, 0.500); P = 0.196; I2 = 65.7% Random-effects vomiting score: SMD: 0.331 (–0.145, 0.808); P = 0.173; I2 = 85.9%	Ginger was more effective for NVP symptoms overall and severity of nausea compared with placebo, but no effect was found for vomiting score. Compared with vitamin B6, no results significantly favored ginger or vitamin B6.
Sridharan et al. [28], 2018	Random-effects model	Nausea scores: direct comparison WMD: –4.2 (–6.5, –1.9); P ≤ 0.05; mixed treatment comparison WMD: –4.7 (–6.0, –3.4); P ≤ 0.05 Vomiting control: pooled OR: 34.9 (3.9, 316.20); P ≤ 0.05	Nausea scores: direct comparison WMD: –0.1 (–0.3, 0.1); P > 0.05; mixed treatment comparison WMD = –0.1 (–0.3, 0.1); P > 0.05	Ginger has therapeutic benefits in the treatment of NVP including decreasing nausea scores and improving vomiting control. However, this was a network MA, and results may change with head-to-head clinical trials. Minimal inconsistency was reported between direct and mixed comparisons.
Matthews et al. [29], 2015	Random-effects and fixed-effects models	n/a	Fixed-effects NVP score day 3: SMD: 0.0 (–0.25, 0.25); P = 0.99; I2 = 0% Random-effects no symptom improvement: average RR: 0.84 (0.47, 1.52); P = 0.57; I2 = 51.85%	Evidence for ginger over placebo was limited and no MA was conducted; however, individual studies show benefit of ginger over placebo. No difference was shown between vitamin B6 and ginger NVP symptom scores on treatment day 3 or for the number of patients reporting no improvement in symptoms.
Viljoen et al. [30], 2014	Random-effects and fixed-effects models	Fixed-effects nausea scores: MD: 1.20 (0.56, 1.84); P = 0.0002; I2 = 0% Random-effects vomiting scores: MD: 0.72 (–0.03, 1.46); P = 0.06; I2 = 71%	Random-effects nausea scores: MD: 0.34 (–1.52, 2.20); P = 0.72; I2 = 91% Random-effects vomiting scores: MD: –0.07 (–0.48, 0.35); P = 0.76; I2 = 44%	Ginger significantly improved nausea scores compared with placebo and was not significant for reducing vomiting. Ginger did not reduce nausea or vomiting symptoms compared with vitamin B6.
Thomson et al. [31], 2014	Random-effects model	NVP overall: pooled OR: 4.89 (1.88, 12.73); Q-statistic = 33.72	n/a	Ginger treatment was more effective than comparators on reducing NVP symptoms overall. However, a vitamin B6 comparison study was included in the placebo comparison which may have diluted the effect of ginger compared with placebo.

Abbreviations: MA, meta-analysis; MD, mean difference; NVP, nausea and vomiting of pregnancy; OR, odds ratio; RR, risk ratio; SMD, standardized mean difference; WMD, weighted mean difference.