Vitamin B-12 and Perinatal Health

Abstract

Vitamin B-12 deficiency (<148 pmol/L) is associated with adverse maternal and neonatal outcomes, including developmental anomalies, spontaneous abortions, preeclampsia, and low birth weight (<2500 g). The importance of adequate vitamin B-12 status periconceptionally and during pregnancy cannot be overemphasized, given its fundamental role in neural myelination, brain development, and growth. Infants born to vitamin B-12-deficient women may be at increased risk of neural tube closure defects, and maternal vitamin B-12 insufficiency (<200 pmol/L) can impair infant growth, psychomotor function, and brain development, which may be irreversible. However, the underlying causal mechanisms are unknown. This review was conducted to examine the evidence that links maternal vitamin B-12 status and perinatal outcomes. Despite the high prevalence of vitamin B-12 deficiency and associated risk of pregnancy complications, few prospective studies and, to our knowledge, only 1 randomized trial have examined the effects of vitamin B-12 supplementation during pregnancy. The role of vitamin B-12 in the etiology of adverse perinatal outcomes needs to be elucidated to inform public health interventions.

Keywords: child health; cobalamin; one-carbon metabolism; pregnancy; vitamin B-12.

FIGURE 1

Vitamin B-12 in 1-carbon metabolism. Vitamin B-12 deficiency prevents remethylation of homocysteine to methionine; results in an accumulation of 5-methyl-THF, or “folate trap,” decreasing the THF pool for synthesis of 10-formyl-THF; and impairs subsequent purine and thymidylate synthesis. MTHFD1, methylenetetrahydrofolate dehydrogenase 1; MTHFR, methylenetetrahydrofolate reductase; MTR, methionine synthase; tHcy, total homocysteine; THF, tetrahydrofolate.

FIGURE 2

Search strategy. A diagrammatic representation of the retrieval strategy used for identifying and selecting studies for inclusion in the final analysis.