Vitamin D in Pregnancy and Lactation: A New Paradigm

Abstract

While much has been written about the importance of vitamin D during the lifespan, its greatest impact appears to be during pregnancy and lactation, affecting not only the mother but her growing fetus and, later, growing infant. Controversy surrounds the daily requirement for vitamin D and what constitutes sufficiency during these critical periods. A growing body of literature supports the importance of vitamin D supplementation during pregnancy to achieve a total circulating 25(OH)D concentration of at least 40 ng/mL, the point at which the conversion of 25(OH)D to 1,25(OH)2D is optimized. This level is associated with a lower risk of comorbidities of pregnancy and better outcomes. During lactation, a maternal daily dose of 6000 IU vitamin D/d is effective and safe at elevating milk vitamin D delivery to the recipient infant in such a manner that those infants do not require an additional vitamin D supplement. These infants also achieve a comparable total circulating 25(OH)D concentration compared to infants supplemented with 400 IU/day. Further, past data suggesting that vitamin D is a teratogenic compound are not well supported in the extant literature. To the contrary, significant amounts of vitamin D are required during pregnancy to protect the mother and fetus and impart genomic imprinting on the fetus to ensure long-term health. With enhanced knowledge about vitamin D's role as a preprohormone, it is clear that recommendations for supplementation should mirror what is clinically relevant and evidence-based.