thereby increasing their probability of B12 deficiency due to reduced absorption. Pregnancy, lactation and early childhood The U.S. Recommended Dietary Allowance (RDA) for pregnancy is 2.6 µg/day, for lactation 2.8 µg/day. Determination of these values was based on the RDA of 2.4 µg/day for non-pregnant women plus what will be transferred to the fetus during pregnancy and what will be delivered in breast milk. However, looking at the same scientific evidence, the European Food Safety Authority (EFSA) sets adequate intake (AI) at 4.5μg/day for pregnancy and 5.0 μg/day for lactation. Low maternal vitamin B12, defined as serum concentration less than 148 pmol/L, increases the risk of miscarriage, preterm birth and newborn low birth weight. During pregnancy the placenta concentrates B12, so that newborn infants have a higher serum concentration than their mothers. As it is recently absorbed vitamin content that more effectively reaches the placenta, the vitamin consumed by the mother-to-be is more important than that contained in her liver tissue. Women who consume little animal-sourced food, or who are vegetarian or vegan, are at higher risk of becoming vitamin depleted during pregnancy than those who consume more animal products. This depletion can lead to anemia, and also an increased risk that their breastfed infants become vitamin deficient. Low vitamin concentrations in human milk occur in families with low socioeconomic status or low consumption of animal products. Only a few countries, primarily in Africa, have mandatory food fortification programs for either wheat flour or maize flour; India has a voluntary fortification program. What the nursing mother consumes is more important than her liver tissue content, as it is recently absorbed vitamin that more effectively reaches breast milk. Breast milk B12 decreases over months of nursing in both well-nourished and vitamin-deficient mothers. Exclusive or near-exclusive breastfeeding beyond six months is a strong indicator of low serum vitamin status in nursing infants. This is especially true when the vitamin status was poor during the pregnancy and if the early-introduced foods fed to the still breastfeeding infant are vegan. Risk of deficiency persists if the post-weaning diet is low in animal products. Signs of low vitamin levels in infants and young children can include anemia, poor physical growth and neurodevelopmental delays. Children diagnosed with low serum B12 can be treated with intramuscular injections, then transitioned to an oral dietary supplement. Gastric bypass surgery Various methods of gastric bypass or gastric restriction surgery are