Vitamin B₁₂ and Neural-Tube defects

Molloy, A. M. et al. Maternal vitamin B12 status and risk of neural tube defects in a population with high neural tube defect prevalence and no folic acid fortification. Pediatrics 123, 917–923 (2009).

Low maternal vitamin B₁₂ status is an independent risk factor for having a child with a neural-tube defect, according to a study published in Pediatrics.

Adequate intake of folic acid can prevent the majority of neural-tube defects. Fortification of grain with folic acid in countries including the US has reduced the prevalence of these defects; however, further folic-acid fortification is unlikely, as concerns about possible adverse effects exist. To further reduce prevalence of neural-tube defects, additional, modifiable maternal risk factors for these defects must be identified. Molloy and colleagues focused on vitamin B₁₂, because of its close metabolic association with folate and evidence of a link between low maternal levels of the vitamin and pregnancies affected by neural-tube defects.

In three separate, nested, case–control studies, the investigators analyzed concentrations of vitamin B₁₂ in blood samples taken from pregnant women at an average 15 weeks of gestation who had a child with neural-tube defects at either that pregnancy or a previous one. Crucially, the samples used (from the 1980s) predated widespread folic-acid fortification.

In all three groups (after adjustment for folate) women with vitamin B₁₂ concentrations in the lowest quartile had a twofold to threefold increased risk of having a child with a neural-tube defects compared with those in the highest quartile. The majority of risk was associated with vitamin B₁₂ concentrations of <184 pmol/l.

The researchers conclude that folate and vitamin B₁₂ jointly influence a woman's risk of having a child with neural-tube defects and that women can reduce this risk by ensuring that they have adequate vitamin B₁₂ levels before they become pregnant.