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Vitamin B12 and Gestational Diabetes Mellitus: A Systematic Review and Meta-analysis.

BACKGROUND/OBJECTIVES
With increasing focus on vitamin B12 and gestational diabetes mellitus (GDM) recently, their relationship remains controversial. To comprehensively evaluate the relationship between vitamin B12 and GDM, and to provide more information on GDM prevention, this study provides a systematic review and meta-analysis of vitamin B12 and GDM.


METHODS
As of September 22, 2021, 304 articles were searched in PubMed, Web of Science, EMBASE, and Cochrane databases, of which 15 studies met the inclusion criteria. The keywords were vitamin B 12 and Diabetes, Gestational. Data were analyzed using R 4.1.0 software. Relative risks were analyzed using random and fixed-effects models to analyze mean differences (MD) for continuous variables; odds ratios (OR) of exposures and 95% confidence intervals (95% CI). Subgroup analysis was used to identify heterogeneity.


RESULTS
There was no association between maternal vitamin B12 concentration during the first trimester with GDM, however, low vitamin B12 concentration in the second or third trimester of pregnancy was related to an increased risk of GDM. Compared with the non-GDM group, the vitamin B12 concentration in the GDM group was remarkably decreased (MD: -10.79; 95%CI: -21.37, -0.21), and vitamin B12 deficiency increased the risk for GDM (OR: 1.59; 95%CI: 1.10, 2.29). These effects were more significant among Asians. In addition, an increased ratio of high folate to low vitamin B12 in serum also increased the risk of GDM (OR: 1.87; 95% CI: 1.46, 2.41).


CONCLUSIONS
In the second or third trimester of pregnancy, vitamin B12 deficiency was associated with GDM, as well as the ratio of high folate and low vitamin B12 as a risk factor for GDM. It is speculated that more vitamin B12 may need to be provided during pregnancy. To improve maternal and child health and more comprehensively understand the relationship between Vitamin B12 and GDM, more research was needed especially the detection of vitamin B12 during the first trimester.