Gut and Gastric Dysbiosis in Hyperemesis Gravidarum: A Scoping Review of Microbiome-Targeted Evidence and Translational Pathways.

Background: Hyperemesis gravidarum (HG) is defined by severe nausea and/or vomiting beginning in early pregnancy, impaired ability to eat or drink normally, and a marked restriction of daily activities. Although gastrointestinal dysbiosis has been proposed in HG, its role remains uncertain within the emerging growth differentiation factor 15 (GDF15)-centered model of susceptibility. Methods: Guided by PRISMA-ScR, this scoping review searched PubMed/MEDLINE, Scopus, Web of Science, publisher websites, and reference lists for contemporary evidence published between 1 January 2021 and 2 May 2026. Pre-2021 foundational publications were excluded from the charted evidence map and included-study count and were cited only as methodological or biological background. Results: Thirty-six sources of evidence were synthesized across five thematic domains. Direct human studies identified associations between HG and altered microbial diversity or composition, as well as gastric Conclusion: Current evidence supports dysbiosis as an associated modifier, consequence, or endotype marker rather than an established independent cause of HG. Priority studies should use Windsor-compatible definitions, early longitudinal sampling, harmonized sequencing and metabolomic methods, concurrent assessment of GDF15 and nutritional status, and biologically stratified trials of confirmed H. pylori infection or reproducible functional dysbiosis.