ObjectiveTo systematically review the association between folic acid supplementation before and/or during pregnancy and the risk for gestational diabetes mellitus (GDM). MethodsThe PubMed, EMbase, The Cochrane Library, SinoMed and CNKI databases were searched to collect studies on folic acid supplementation and GDM from inception to November 2021. Two reviewers independently screened the literature, extracted data, and assessed the risk of bias of the included studies. Meta-analysis was then performed using RevMan 5.4 software. ResultsA total of 19 studies involving 53 128 cases were included. The results of meta-analysis showed that there was no significant association between folic acid supplementation and the risk for GDM (RR=0.98, 95%CI 0.85 to 1.13, P=0.74). Subgroup analysis revealed that folic acid supplementation was associated with a decreased risk for GDM in Europe and the United States (RR=0.81, 95%CI 0.71 to 0.92, P<0.001), in areas that fortified grain cereal products with folic acid (RR=0.81, 95%CI 0.69 to 0.94, P=0.005). ConclusionThere is no significant association between folic acid supplementation and the risk for GDM. However, supplementation may decrease the risk for GDM among women in Europe and the United States. Due to the limited quantity and quality of the included studies, more high-quality studies are needed to verify the above conclusion.