1,25-Dihydroxyvitamin D Deficiency Is Associated With Preterm Birth in African American and Caucasian Women

Vitamin (vit) D deficiency and preterm birth (PTB) are more prevalent among African American (AA) women compared to caucasian (Cau) women. Because vit D is important in regulating cell-mediated immune responses, vit D insufficiency or deficiency during pregnancy may enhance inflammation in pregnant women and increase the risk of PTB. In this study, circulatory levels of 25-hydroxy (OH) and 1,25-dihydroxy (OH)₂ vit D were measured using chemiluminescence and radioimmunoassay techniques, respectively, in AA (n = 108) and Cau (n = 84) women who delivered at term and preterm. The results from this study suggest that the serum levels of the 25-(OH) vit D concentrations tend to decrease (P = .06) in the Cau women who delivered at preterm compared to those delivering at term. However, the 25-(OH) vit D levels in Cau and AA between term and preterm deliveries were not significantly different. The serum levels of 1,25-(OH)₂ vit D were found to be significantly lower in AA women compared to Cau women (P < .02) at term, and in the Cau (P < .01) and AA (P < .04) women delivering at preterm compared to those delivering at term. One-way analysis of variance demonstrated that 1,25-(OH)₂ vit D levels were significantly lower in participants delivering at preterm (<34 weeks and between 34 and 37 weeks) compared to those delivering at term (>37 weeks).These results suggest that low levels of serum 1,25-(OH)₂ vit D are associated with PTB, and vit D can potentially be used as a novel diagnostic marker in the detection of PTB.