Reversed seasonal variation in maternal vitamin D levels in southern Louisiana.

Vitamin D is critical in bone and mineral homeostasis, particularly in the prevention of rickets in children. Levels of vitamin D in cord blood were measured in a population from New Orleans as an index of maternal vitamin D status at the time of delivery. Cord blood samples from infants born during the summer and winter showed lower 25-hydroxyvitamin D levels compared with those from infants born during fall and spring, indicating an unusual pattern of seasonality where vitamin D levels were among the lowest in the season with the greatest sunlight. It is important to establish screening and supplementation guidelines based on observed regional trends and risk factors, in addition to considerations based on global recommendations.