Beyond Folate: The Emerging Role of Maternal Vitamin B12 in Neural Tube Development

Background/Objectives: Folic acid (FA) supplementation can effectively reduce the occurrence of neural tube defects (NTDs). Vitamin B12 is involved in folate metabolism; however, studies have not reached a definitive conclusion on the association between vitamin B12 and NTDs independent of folate levels. A systematic review and meta-analysis were performed to summarize existing research and investigate the effect of vitamin B12 on NTDs. Methods: Studies were systematically searched in PubMed, Web of Science, Embase, and Cochrane, published before 1 March 2024. Standardized mean difference (SMD) with 95% confidence interval (CI) was employed to assess the association between maternal vitamin B12 in blood and NTDs. Results: A total of 38 studies were included, with a total of 2316 NTDs and 4298 controls, covering 14 countries worldwide. Compared with the non-NTD group, the NTD group exhibited a lower vitamin B12 level [SMD = -0.23, 95% CI (-0.32, -0.14), p < 0.001, I² = 58.3%] with a statistically significant difference. Additionally, there was a significant association between maternal vitamin B12 concentration and NTDs when there was no significant difference in folate between the NTD and control groups [SMD: -0.19, 95% CI (-0.28, -0.10)]. Conclusions: Vitamin B12 supplement is also essential for the prevention of NTDs besides folic acid. Monitoring vitamin B12 concentration among pregnant women and considering appropriate supplementation with a combination of vitamin B12 and folic acid could be explored.