Treatment of Nausea and Vomiting With Zingiber officinale in Pregnancy: An Umbrella Review of Systematic Reviews With Meta‐Synthesis

ABSTRACT

Affecting approximately 85% of expectant mothers during the first trimester, nausea and vomiting of pregnancy (NVP) are frequently reported symptoms. Despite numerous existing systematic reviews and meta‐analyses (SRMs), findings remain inconsistent. Consequently, this study assesses the quality of these prior SRMs and investigates the efficacy of ginger as a treatment for NVP. A comprehensive search was conducted across PubMed, Scopus, Cochrane, and Web of Science from their inception through December 30, 2024. This review includes peer‐reviewed English‐language SRMs investigating ginger as a therapeutic intervention for pregnancy‐related nausea and vomiting. Methodological rigor was evaluated using the AMSTAR‐2 checklist, while evidence quality was assessed via the GRADE approach. Findings are synthesized narratively through content analysis. The study protocol was prospectively registered in the PROSPERO database. This study analyzed 18 systematic reviews, of which eight (44%) incorporated meta‐analyses. The Rhodes Index of Nausea and Vomiting (RINV) emerged as the primary tool for evaluating outcomes. Regarding study reporting and transparency, seven studies registered their protocols in PROSPERO, while eight adhered to the PRISMA checklist. Overall, the included reviews demonstrated low methodological quality, with a mean score of 11.77. Specifically, 28% (n = 5) were rated as high quality, 28% (n = 5) as moderate, 22% (n = 4) as low, and 22% (n = 4) as critically low. Taking ginger supplements (usually between 450 and 1950 mg daily) significantly decreases the severity and occurrence of nausea and vomiting compared to a placebo. This benefit is more noticeable for nausea than for vomiting, where the results are less consistent. Numerous studies have shown that ginger does not raise the risk of adverse effects, such as spontaneous abortion or side effects like heartburn and drowsiness, when compared to a placebo or vitamin B6. Current evidence clearly shows that ginger is a safe and effective treatment for nausea and vomiting during pregnancy, with effectiveness similar to vitamin B6 and some traditional medications, and it has a good safety profile. Ginger can be recommended as a dependable medicinal herb for women dealing with NVP, though more research is needed to determine the best doses and confirm long‐term safety.

1. Introduction

Nausea and vomiting of pregnancy (NVP), including symptoms of nausea, retching, and/or vomiting, is one of the common complaints during pregnancy that is experienced by 85% of pregnant women in early pregnancy (Maltepe and Koren 2013). Although NVP is mostly called “morning sickness” but, it is reported by 80% of pregnant women throughout the day and not just in the morning (Gadsby et al. 2020). Based on a previous study, one out of two pregnant women faces NVP; it represents the high burden of this disease. The symptoms of NVP usually resolve until 16–20 weeks of pregnancy, and a few cases persist until late pregnancy (Liu et al. 2022).

NVP based on its severity was categorized as mild, moderate, and severe. Hyperemesis gravidarum (HG) is the most severe type of NVP, and it is observed in 0.3%–10.8% of pregnant women (Fejzo et al. 2019). HG was first defined in 1956 by the American Pharmaceutical and Chemical Boards as hospitalized women with refractory vomiting. It includes inability to eat and/or drink normally, electrolyte balance changes, weight loss ≥ 5%, ketosis and ketonuria, neurological disorders, liver damage, retinal hemorrhage, and kidney damage (Jansen et al. 2021).

The underlying pathophysiology of NVP has not been understood; but it was clarified that it is multifactorial. In this context, gene expression has been identified as a risk factor for HG and NVP. Vikanes et al. showed HG can cross generations; for example, a 3‐fold significant increase has been reported in the risk of HG for daughters of mothers with HG, and (Vikanes et al. 2010) also, having a sister with HG increases risk by 17‐fold (Zhang et al. 2011). Endocrine factors including Human chorionic gonadotropin (hCG), estrogen, and progesterone, growth/differentiation factor 15 (GDF15), Helicobacter pylori infection (in HG), upper intestinal motility disorder, placental factors (weight of the placenta, placental hormones, genes expressed in the placenta GDF15, IGFBP7), and psychological disorders are other factors that have been addressed (Liu et al. 2022).

The hCG hormone, secreted by the placental cytotrophoblast cell layer, has been widely accepted as an important factor in the pathogenesis of NVP and HG. hCG up‐regulation in early pregnancy occurs at the same time that symptoms of NVP and HG start (Kaňková et al. 2023). Additionally, in 2021, Zhang et al. identified GDF15 in the area postrema of the brain for nausea‐associated behaviors. GDF15, a member of the Transforming Growth Factor‐β (TGF‐β) superfamily, which is secreted by the placenta, and its higher levels, like hCG in early pregnancy, are associated with stronger NVP and a higher risk of HG (Zhang et al. 2021).

Various mechanisms are involved in the pathophysiology of NVP, most of which are unknown. Different pharmacological approaches, such as H1 receptor antagonist, selective 5‐HT3 receptor antagonist, Pyridoxine (vitamin B6), antihistaminergic medication, and non‐pharmaceutical methods (acupuncture, acupressure, and ginger) are used for NVP treatments (Liu et al. 2022). However, oral antiemetic drugs can impact human physiology of the mother, including plasma volume, intestinal motility, and glomerular filtration; and in relation to the fetus, the drug can cross the placenta. Therefore, it is crucial to use interventions as non‐pharmacological therapy, which have minimal side effects for the mother and fetus in NVP treatment (Sumah et al. 2021).

Ginger is a perennial herb that has a long history of wide spectrum usage, from a home remedy for gastric ailments to a common ingredient in Asian meals. Treatment with ginger is easily available, convenient (Volqvartz et al. 2019). However, findings of studies are conflicting, such as an internet‐based survey of women with HG, which showed that 88% considered it completely ineffective and 51% reported that their symptoms exacerbated, and also, 79% of women were disturbed in their confidence and trust in the health care professional who recommended taking ginger (Dean and O'Hara 2015). Another study indicated that ginger was effective in reducing the severity of general NVP symptoms and nausea but had no significant effect on vomiting compared with a placebo (Hu et al. 2022). Therefore, this study aimed to evaluate the quality of published systematic reviews and meta‐analysis and investigate the therapeutic effect of Ginger on treating NVP in pregnancy.

2. Methods

This umbrella review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines (Page et al. 2021). The study protocol was registered in the PROSPERO database prior to the commencement of the study (ID: CRD42024610894).

2.1. Eligibility Criteria

All systematic reviews and meta‐analyses (SRMs) that investigated ginger as an intervention in comparison with other control groups for the treatment of pregnancy‐associated nausea and vomiting, published in EN and peer review journals, were included in this review. We used the PICOT‐SD framework as follows (Riva et al. 2012): Population: pregnant women; Intervention: all types of ginger; Comparison: all other comparisons, including traditional pharmaceutical products (vitamin B6 and doxylamine), placebo, complementary medicine (wristband and acupuncture), or control; Outcome: decreasing the NVP in pregnancy; Timing: without limitation until December 2024; Study design: all systematic reviews and meta‐analyses that included RCTs. Studies with unavailable full text, other languages than EN, or a lack of data regarding our intervention and outcome of interest were excluded from this review.

2.2. Information Sources and Search Strategy

Four main databases of PubMed, Scopus, Cochrane, and Web of Science were searched from inception to 4 November 2024. Our search was conducted without limitation regarding time or language. Also, we searched the reference list of the included studies, and contacted corresponding authors in the full text that was not available. We used a combination of MeSH and free terms to capture all relevant articles. Our main keywords were ginger, nausea, vomiting, and pregnancy. The initial search was piloted in PubMed, and after finalizing the search strategy, one author searched databases (MA‐Z). The full search strategies for all databases are presented in Supporting Information: File S1.

2.3. Selection Process

After completing the search, the overall records were imported to EndNote software Version 20 and duplicates removed. We piloted the screening with 10 records, and after reaching an agreement of 90% or above, the screening started. Then, two independent reviewers (ZTG, ME) screened the records based on title, abstract, and full text, considering the inclusion and exclusion criteria. Potential discrepancies were solved using consultation with a third reviewer (MA‐Z). We generated the flow diagrams using the Shiny App available at https://www.eshackathon.org/software/PRISMA2020.html (Haddaway et al. 2022).

2.4. Data Collection Process and Data Items

After the screening was completed, data extraction was started. We extracted the following data items from the included studies: first author name, publication year, country, databases, search period, number of the included studies in each systematic review or meta‐analysis, intervention, comparison, outcome assessment tools, quality appraisal checklist name, registration information, funding information, and specific results regarding outcome of interest. We piloted the data extraction checklist with two records, and after reaching an agreement of 90% or above, the data extraction started. Two independent reviewers extracted the data (ZTG, ME). A third reviewer rechecked the information and resolved the potential discrepancies (MA‐Z).

2.5. Quality Appraisal and Grading

The overall quality of the included SRMs was determined using the A Measurement Tool to Assess Systematic Reviews (AMSTAR‐2) checklist to yield a score ranging from 1 to 16 (Shea et al. 2017). Also, the quality of evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) framework, categorized as high, moderate, critically low, or low quality (Granholm et al. 2019). We piloted the appraisal checklist with two records, and after reaching an agreement of 90% or above, the quality appraisal started. Two independent reviewers appraised the included SRMs (ZTG and ME). A third reviewer rechecked the information and solved the potential discrepancies (MA‐Z).

2.6. Synthesis Methods

In cases of systematic reviews without meta‐analysis, we employed a narrative approach to synthesize the results. We used content analysis using Mapify: AI Mind Map Summarizer (https://mapify.so/app) for categorizing the results. Also, we report the results using tables, figures, and charts.

3. Results

3.1. Study Selection

A total of 133 records were retrieved from the databases. After duplicates were removed, 112 records were screened by title, abstract, and full‐text based on eligibility criteria, of which 18 studies were included in the final review (Hu et al. 2022; AlHajri et al. 2017; Anh et al. 2020; Borrelli et al. 2005; Dante et al. 2013; Ding et al. 2013; Gaur et al. 2022; Jayawardena et al. 2023; Khorasani et al. 2020; Matthews et al. 2015; McParlin et al. 2016; Nassif et al. 2022; O'Donnell et al. 2016; Ozgoli and Saei Ghare Naz 2018; Sridharan and Sivaramakrishnan 2018; Tan et al. 2023; Thomson et al. 2014; Viljoen et al. 2014). Two studies were excluded after full‐text screening. The reasons for exclusion were as follows: Non‐English study (one record), other type of review (one record) (Betz et al. 2005; Chrubasik et al. 2005). The PRISMA flow diagram for the complete study selection process is presented in Figure 1.

FIGURE 1.

PRISMA flow diagram for search and selection process.

3.2. Study Characteristics

Studies were published between 2005 and 2023, of which most were published in 2022. In eight cases (0.44%), meta‐analysis was also performed. The number of RCTs included in these SRMs was between 4 and 19. The largest number of the included SRMs was related to the countries of Iran, Italy, the UK, and China, each of which had two studies. The most common comparison groups among the included studies were Vit B6 and placebo. The most used tools for quality appraisal in the included studies were RoB‐2 (11 studies) and Jadad's checklist (five studies). The most important tool used to evaluate the outcome of the study was the Rhodes index of nausea and vomiting (RINV). Seven studies had registered their protocol in the PROSPERO database before starting the study. Eight studies followed the PRISMA checklist for study reporting. Also, five studies have stated that they used funds to conduct their study. More details about the characteristics of the included systematic reviews are presented in Table 1.

TABLE 1.

Summary characteristics of the included studies.

Author, year	Country a	Databases	Search	Included studies/Ginger	Participants	Intervention	Comparison	Meta‐analysis	Outcome assessment tool	Quality appraisal checklist	Registration	PRISMA	GRADE	Funding
AlHajri et al. 2017 (Khorasani et al. 2020)	UAE	3 PubMed Scholar Science direct	2007–2017	5 RCTs	505	Ginger	Vit B6 Placebo Acupressure	No	RINV VAS Likert	Jadad Score	No	Yes	No	No
Borrelli et al. 2005 (McParlin et al. 2016)	Italy	3 Medline EMBASE Cochrane	Up to June 2004	6 RCTs	600	Ginger	Placebo Vit B6	No	RINV VAS Likert	Jadad Score	No	No	No	NR
Dante et al. 2013 (Nassif et al. 2022)	Italy	4 Medline AMED Cochrane PDR	1990 to December 2010	10 RCTs	1098	Ginger	Vit B6 Placebo Dimenhydrinate	No	RINV VAS	Jadad Score	No	No	No	NR
Ding et al. 2013 (O'Donnell et al. 2016)	Australia	4 CINAHL Cochrane Medline TRIP	2000–2009	4 RCTs	504	Ginger syrup Ginger capsule Ginger extract	Placebo	No	RINV	CASP	No	No	No	NR
Gaur et al. 2022 (Ozgoli and Saei Ghare Naz 2018)	India	3 PubMed EMBASE Scopus	Up to 2021	7 RCTs	763	Ginger capsule Ginger powder	Vit B6	Yes	RINV	RoB‐2	Yes	Yes	No	NR
Anh et al. 2020 (Matthews et al. 2015)	Korea	6 PubMed EMBASE Cochrane ClinicalTrials.gov KISS NDSL	Up to July 2019	10 RCTs	1927	Ginger capsule Ginger powder Ginger extract	Placebo	No	RINV	RoB‐2	No	Yes	No	Yes
Hu et al. 2022 (Anh et al. 2020)	China	2 WoS, PubMed	Up to April 2019	13 RCTs	1174	Ginger capsule ginger powder capsules	Placebo Vit B6 Acupressure metoclopramide	Yes	RINV VAS Likert	RoB‐2	No	No	No	Yes
Jayawardena et al. 2023 (Sridharan and Sivaramakrishnan 2018)	Sri Lanka Australia	3 PubMed WoS Scopus	Up to May 2021	18 RCTs	3893	Vit B6	Ginger Placebo Acupressure	Yes	RINV PUQE	NR	No	Yes	No	No
Khorasani et al. 2020 (Tan et al. 2023)	Iran	3 PubMed Cochrane Scopus	Up to January 2019	17 RCTs	1064	Ginger capsule Ginger syrup Ginger biscuits Ginger powder	Vit B6 Placebo Lactose Normal saline	No	RINV VAS	Jadad Score	No	No	No	NR
Matthews et al. 2015 (Thomson et al. 2014)	Ireland	Cochrane Medline EMBASE CINAHL EBSCO	Up to January 2015	14 RCTs	1608	Ginger syrup Ginger capsule Ginger powder Ginger extract	Placebo Vit B6	Yes	RINV VAS PUQE	RoB‐2	Yes	No	Yes	Yes
McParlin et al. 2016 (Viljoen et al. 2014)	UK	10 Medline EMBASE CINAHL Cochrane PsychINFO CAB abstract Scopus NHS EED HEED CNKI	Up to June 2016	17 RCTs	8930	Ginger	Vit B6 Placebo	No	RINV VAS	RoB‐2	Yes	No	Yes	Yes
Nassif et al. 2022 (Betz et al. 2005)	Brazil	13 Medline PubMed EMBASE CINAHL Cochrane WoS Scopus ICTRP LILACS CUMED IBECS ReBEC CNKI	1988–2020	9 RCTs	908	Ginger capsule Ginger syrup	Placebo Vit B6	No	RINV VAS PUQE	RoB‐2	Yes	Yes	No	No
O'Donnell et al. 2016 (Chrubasik et al. 2005)	UK	10 Medline EMBASE CINAHL Cochrane PsychINFO CAB abstract Scopus NHS EED HEED CNKI	Up to September 2014	16 RCTs	1339	Ginger	Vit B6 Placebo	No	RINV VAS	RoB‐2	Yes	No	Yes	Yes
Ozgoli and Saei Ghare Naz 2018 (38)	Iran	3 PubMed Scopus Scholar	2000–2015	10 RCTs	2224	Ginger capsule Ginger syrup Ginger biscuits Ginger powder	Placebo	No	RINV VAS MPUQE	Jadad Score	No	No	No	No
Sridharan and Sivaramakrishnan 2018 (39)	Fiji	PubMed Cochrane Google Scholar	1980–2017	19 RCTs	2615	Ginger biscuits Ginger syrup Ginger capsule	Placebo Vit B6	Yes	NR	RoB‐2	Yes	Yes	Yes	No
Tan et al. 2023 (40)	China	8 PubMed EMBASE Cochrane WoS CNKI Wanfang SinoMed VIP	Up to October 2022	14 RCTs	1445	Ginger	Placebo Conventional medicine	Yes	RINV VAS	RoB‐2	Yes	Yes	Yes	NR
Thomson et al. 2014 (41)	Canada	5 PubMed EMBASE CINAHL Cochrane OVID	NR	6 RCTs	508	Ginger capsule Ginger syrup Ginger powder	Placebo Vit B6	Yes	RINV VAS	RoB‐2	No	Yes	No	No
Viljoen et al. 2014 (42)	South Africa	12 Medline EBSCO CINAHL CAB abstract Cochrane WoS Science Direct ISAP ProQuest Scopus SABINET Clinicaltrial.gov	Up to July 2013	12 RCTs	1278	Ginger capsule Ginger powder Ginger extract Dried root Fresh root	Placebo Active ingredient	Yes	RINV VAS Likert MOS short	RoB‐2	Yes	No	No	NR

Abbreviations: HEED: Health Economic Evaluation Database; MPUQE: Pregnancy‐Unique Quantification of Emesis and Nausea; NHS EED: National Health Service Economic Evaluation Database; NR: not reported; PUQE: Pregnancy‐Unique Quantification of Emesis; RINV: Rhodes index of nausea and vomiting; ROB‐2: Cochrane Risk of Bias Assessment Tool; VAS: Visual Analogue Scale.

^a Country for corresponding author.

3.3. Quality Appraisal and Grading

The overall score of the included studies was 11.77, which was graded as an overall low quality. However, five of the studies were graded as high quality (28%), five were of moderate quality (28%), four were of low quality (22%), and four were of critically low quality (22%), respectively. The first question, which was related to the research question, inclusion criteria, and its compliance with PICO reporting, received the highest score among the studies, with a score of 18, and question 15, which was about how to examine and report publication bias, received the lowest score among the studies, with a score of seven. More details about the quality appraisal of the included systematic reviews are presented in Table 2 and Figure 2.

TABLE 2.

Quality appraisal of the included studies.

Author, year	Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8	Q9	Q10	Q11	Q12	Q13	Q14	Q15	Q16	Overall	GRADE
AlHajri et al. 2017 (Khorasani et al. 2020)	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	N	N	N	N	N	Y	11	Low
Borrelli et al. 2005 (McParlin et al. 2016)	Y	PY	Y	Y	Y	Y	Y	Y	Y	N	N	N	N	N	N	N	8.5	Low
Dante et al. 2013 (Nassif et al. 2022)	Y	PY	Y	Y	N	N	PY	Y	Y	N	N	N	N	N	N	Y	7	Critically Low
Ding et al. 2013 (O'Donnell et al. 2016)	Y	N	Y	Y	N	N	Y	Y	Y	N	N	N	N	N	N	N	6	Critically Low
Gaur et al. 2022 (Ozgoli and Saei Ghare Naz 2018)	Y	Y	Y	Y	Y	Y	Y	Y	Y	N	Y	Y	Y	Y	Y	Y	15	High
Anh et al. 2020 (Matthews et al. 2015)	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	N	N	Y	N	N	Y	12	Moderate
Hu et al. 2022 (Anh et al. 2020)	Y	Y	Y	PY	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	15.5	High
Jayawardena et al. 2023 (Sridharan and Sivaramakrishnan 2018)	Y	Y	Y	Y	Y	Y	Y	Y	N	Y	Y	Y	N	N	N	Y	12	Critically Low
Khorasani et al. 2020 (Tan et al. 2023)	Y	PY	N	PY	Y	Y	Y	Y	N	N	N	N	N	N	N	Y	7	Critically Low
Matthews et al. 2015 (Thomson et al. 2014)	Y	Y	Y	PY	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	N	14.5	High
McParlin et al. 2016 (Viljoen et al. 2014)	Y	Y	Y	PY	Y	N	Y	Y	Y	N	Y	Y	Y	N	Y	Y	12.5	Moderate
Nassif et al. 2022 (Betz et al. 2005)	Y	PY	Y	PY	Y	Y	Y	Y	PY	N	Y	Y	Y	Y	Y	N	12.5	Moderate
O'Donnell et al. 2016 (Chrubasik et al. 2005)	Y	Y	Y	Y	Y	Y	Y	Y	PY	N	Y	Y	Y	N	Y	Y	13.5	Moderate
Ozgoli and Saei Ghare Naz 2018 (38)	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	N	N	Y	N	N	Y	12	Moderate
Sridharan and Sivaramakrishnan 2018 (39)	Y	PY	Y	PY	Y	Y	Y	PY	PY	Y	Y	Y	Y	N	Y	Y	13	High
Tan et al. 2023 (40)	Y	Y	Y	PY	Y	Y	Y	Y	PY	N	Y	Y	Y	Y	Y	Y	14	High
Thomson et al. 2014 (41)	Y	Y	Y	Y	Y	Y	PY	Y	Y	N	Y	Y	Y	Y	N	N	12.5	Low
Viljoen et al. 2014 (42)	Y	PY	Y	Y	Y	Y	Y	PY	PY	Y	Y	Y	N	Y	Y	Y	13.5	Low
Overall	18	14	17	14.5	16	15	17	17	13.5	8	11	11	11	7	9	13	11.77	Low

Note: Y: Yes (1); N: No (0); PY: Partially Yes (0.5). Green, yes; Red, no; Yellow, partially yes.

FIGURE 2.

The level of the included studies based on the GRADE.

3.4. Results of Synthesis

Of the final articles, 10 did not conduct meta‐analysis, and only 8 did. Due to high heterogeneity in the studies, meta‐analysis was not possible in this study, and the results were categorized and reported using content analysis. The overall analysis of the individual SRM is reported in Figures 3 and 4.

FIGURE 3.

Specific results regarding the effectiveness of ginger for the treatment of NVP in the included studies.

FIGURE 4.

A mind map for the overall aspect of ginger for preventing NVP.

The collective evidence from systematic reviews and meta‐analyses consistently indicates that ginger is an effective and generally safe option for alleviating nausea symptoms in pregnancy. Also, the key findings of the content analysis of the included SRMs are presented below.

3.4.1. Efficacy for NVP

Ginger supplementation (typically 450–1950 mg per day) significantly reduces the intensity and frequency of nausea and vomiting compared to placebo. This effect is most pronounced for nausea rather than vomiting episodes, where the benefit is less consistent.

3.4.2. Comparison to Other Treatments

Ginger is at least as effective as vitamin B6 (pyridoxine), a standard first‐line therapy for NVP, with several studies showing no significant difference between the two, and some suggesting ginger may be more effective in certain cases. Compared to antihistamines and metoclopramide, ginger shows similar efficacy with fewer side effects. An overall comparison of ginger with other options is included in Table 3.

TABLE 3.

Ginger versus other interventions for NVP.

Intervention	Effectiveness for nausea	Effectiveness for vomiting	Safety profile
Ginger	Significant benefit	Modest/uncertain benefit	Good, mild side effects
Vitamin B6	Significant benefit	Significant benefit	Good
Placebo	Minimal benefit	Minimal benefit	Good
Antihistamines	Significant benefit	Significant benefit	Some side effects
Metoclopramide	Significant benefit	Significant benefit	More side effects

3.4.3. Safety Profile

Across multiple studies, ginger did not increase the risk of adverse events, including spontaneous abortion or side effects like heartburn and drowsiness, when compared to placebo or vitamin B6. However, the maximum safe dosage and long‐term safety require further research.

3.4.4. Clinical Recommendations

Ginger is widely regarded as a safe, medicinal herb alternative for women seeking relief from NVP, especially for those wishing to avoid medications during pregnancy. It is the only herbal remedy with sufficient clinical evidence to support its use in this context.

3.4.5. Quality and Limitations of Evidence

The quality of existing SRMs on NVP treatments, including ginger and other CAM therapies, is generally low or very low due to small sample sizes, clinical heterogeneity, poor outcome reporting, and risk of bias. There is a need for more rigorously designed, large‐scale, multicenter RCTs to confirm the efficacy and safety of ginger and other CAM therapies for NVP. Current guidelines and reviews often lack comprehensive evidence quality assessments, making clinical decision‐making challenging.

4. Discussion

Based on our results, ginger supplementation (typically 450–1950 mg per day) significantly reduces the intensity and frequency of nausea and vomiting compared to placebo. This effect is most pronounced for nausea rather than vomiting episodes, where the benefit is less consistent. Ginger is at least as effective as vitamin B6 (pyridoxine), a standard first‐line therapy for NVP, with several studies showing no significant difference between the two and some suggesting ginger may be more effective in certain cases. Compared to antihistamines and metoclopramide, ginger shows similar efficacy with fewer side effects. Also, ginger did not increase the risk of adverse events, including spontaneous abortion or side effects like heartburn and drowsiness, when compared to placebo or vitamin B6.

5. Mechanism of Action

Several mechanisms have been proposed with regards to the antiemetic effect produced by ginger, including the carminative effect which breaks up the intestinal gas. This mechanism was supported by the results of a randomized, double‐blind trial which demonstrated the ability of ginger to accelerate gastric emptying and stimulate antral contractions. Some asserted that the antiemetic effect results from the inhibition of serotonin receptors in the gastrointestinal system and the central nervous system ‘vomiting center’, as well as the inhibition of vasopressin which causes a reduction in tachygastric activity (AlHajri et al. 2017).

The antiemetic effect of ginger has been attributed to nonvolatile pungent active ingredients of 6‐gingerol and 6‐shogaol; galanoctone and galano‐lactogen have antiserotonin‐3 (5HT3) effects. The mechanism of action of ginger and its active ingredients on the digestive system has been proven through changes in its movements, including in the study that extract of ginger or gingerol fed orally to mice increased gastrointestinal transport. In general, ginger has central anti‐emetic, anti‐serotonin, anticholinergic properties and anti‐hydroxytryptamine activity (Borrelli et al. 2005; Jayawardena et al. 2023; Khorasani et al. 2020; Ozgoli and Saei Ghare Naz 2018).

6. Effectiveness

In the analysis of all systematic reviews, it is determined that ginger has a significant effect on reducing NVP compared to placebo. On the other hand, ginger has a similar effect compared to metoclopramide and antihistamines, which are effective treatments for NVP. Among the various herbal remedies, ginger is one of the most effective medicinal herbs, which has even been recommended in some articles for hyperemesis gravidarum (Dante et al. 2013).

Given that the first line of treatment for NVP is currently vitamin B6, the most important comparison of ginger is with this chemical drug. A quantitative review of all articles revealed that 11% of the articles indicated the superiority of vitamin B6 and 16% indicated the superiority of ginger over vitamin B6. Therefore, ginger has similar effects to vitamin B6, with relative superiority over it. Although one article noted a decrease in the effectiveness of ginger in the long term and a decrease in the effect on vomiting during pregnancy (Khorasani et al. 2020; Viljoen et al. 2014), this very small number does not affect the overall conclusion that ginger has a relative advantage over vitamin B6. On the other hand, there are also articles that doubt the effectiveness of vitamin B6 on NVP and do not consider it definitive (Borrelli et al. 2005).

One of the reasons for the discrepancy in different articles comparing ginger and vitamin B6 is related to the different doses of ginger (250 mg to 5 g per day) and different pharmaceutical forms (capsule, syrup, extract, powder, biscuits, fresh root, dried root) used.

7. Maternal and Fetal Complications

The studies suggest also that the use of ginger in women with NVP is safe (Ozgoli and Saei Ghare Naz 2018; Sridharan and Sivaramakrishnan 2018; Tan et al. 2023; Thomson et al. 2014; Viljoen et al. 2014). No infant congenital malformations, abnormal pregnancies, or delivery outcomes were recorded as a result of the ginger intervention in the investigations. Ginger also had no effect on gestational age at birth, birth weight, Apgar scores, and frequency of abnormalities. There was also no difference in the rates of postpartum hemorrhage. Of course, pregnant women should be careful about overdose when consuming this herb (Anh et al. 2020; Dante et al. 2013; Ding et al. 2013; Gaur et al. 2022; Matthews et al. 2015). Only one article mentions that in terms of miscarriages, the ginger group reported two events and the vitamin B6 group reported one event (O'Donnell et al. 2016).

8. Non‐Pregnancy Complications

The non‐pregnancy side effects of ginger are very rare and have been reported in a limited number of articles. Some trials reported participants suffered dizziness, stomachache and heartburn after consuming ginger. Stomachache and heartburn may be avoided by administering ginger with small frequent meals (Hu et al. 2022; Gaur et al. 2022). Moreover, ginger can cause hypotension and the possibility of cardiac arrhythmias; hence, cardiac patients should be warned. Furthermore, it is known to cause gastrointestinal irritation and is contraindicated in patients with or who have a history of gallstones as it stimulates secreting bile (AlHajri et al. 2017).

9. Interactions

Most articles do not report any interaction with ginger, and only one article states that this herb might interact with anticoagulants and anti‐platelets as ginger itself has an anticoagulant effect (AlHajri et al. 2017; Dante et al. 2013).

In summarizing the side effects, we concluded that antihistamines and metoclopramide have a good effect on NVP; their side effects, especially the high side effects of metoclopramide, have reduced their use. Among chemical drugs, vitamin B6 has been considered because of its fewer side effects. Ginger has been reported in most studies to have no side effects or to have few side effects, which is the same as vitamin B6.

10. Conclusion

The analyzed data strongly support the potential of ginger as an effective and safe treatment for nausea and vomiting in pregnancy. Ginger's efficacy is comparable to vitamin B6 and other antiemetics, and it is a favorable option within CAM therapies, which overall show promise but suffer from low‐quality evidence. Future research with improved methodological rigor and larger samples is essential to validate these findings and inform clinical guidelines.

Author Contributions

Zoya Tahergorabi: conceptualization, methodology, data curation, validation, investigation, writing – original draft, writing – review and editing. Mahdi Eslami: conceptualization, methodology, investigation, writing – original draft, writing – review and editing, validation, data curation. Morteza Arab‐Zozani: conceptualization, methodology, software, data curation, supervision, project administration, formal analysis, writing – review and editing, writing – original draft, validation, investigation, visualization, resources.

Funding

The authors have nothing to report.

Ethics Statement

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

File S1: Search strategy for all databases.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.