Conclusions
B12 insufficiency, deficiency/depletion
LATE PREGNANCY, VITAMIN B6 DEFICIENCY
Significant proportions of preconception women living in high-income countries have marginal or low status of folate, riboflavin, vitamin B12, and vitamin D, and many develop markers of vitamin B6 deficiency in late pregnancy. In the absence of the intervention supplement, maternal plasma concentrations show differing longitudinal patterns between vitamins from preconception to early and late pregnancy, inconsistent with plasma volume expansion wholly accounting for lower gestational concentrations, and markers of functional B6 and B12 insufficiency increase during pregnancy. Preconception and pregnancy supplementation in amounts available in over-the-counter supplements substantially reduced the prevalence of deficiency/depletion markers before and during pregnancy, and a higher maternal plasma vitamin B12 was maintained during the recommended lactational period. In the setting of increasing advocacy for more diets that are likely to be less nutrient dense, the findings suggest a need to reappraise dietary recommendations for preconception and pregnancy and to consider further the role of multiple micronutrient supplements in women living in higher-income countries.