Vitamin B6 in nausea and vomiting of pregnancy: metabolism, mechanisms, and clinical implications—a narrative review

Nausea and vomiting of pregnancy (NVP), including its severe form, hyperemesis gravidarum (HG), is a common condition during early pregnancy, with complex and incompletely understood pathophysiological mechanisms. In recent years, attention has increased toward the potential role of vitamin B6 in the management of NVP. This narrative review aims to summarize and integrate current evidence on vitamin B6 metabolism, pregnancy-related physiological changes, potential mechanisms of action, clinical efficacy, safety, and relevant international guideline recommendations in NVP. Current evidence generally supports vitamin B6 as a first-line foundational treatment for mild-to-moderate NVP, particularly when combined with doxylamine, demonstrating favorable clinical utility. Emerging evidence suggests that vitamin B6 may contribute to the development and regulation of NVP through multiple pathways, including neurotransmitter metabolism, neuroendocrine regulation, and mechanisms of the gut-brain axis. However, direct clinical evidence supporting these mechanistic links remains limited. Future studies integrating biomarkers, neuroendocrine pathways, and high-quality clinical investigations are warranted to further clarify the mechanistic role and clinical value of vitamin B6 in NVP.