Vitamin D and corticotropin-releasing hormone in term and preterm birth: potential contributions to preterm labor and birth outcome.

BACKGROUND: Poor maternal vitamin D status and elevated circulating corticotropin-releasing hormone (CRH) are associated with preterm birth. It is not known if these risk factors are independent or interrelated. Both are associated with inflammation.

METHODS: We measured maternal circulating 25-hydroxyvitamin D (25-OH-D) and CRH from 97 samples collected from 15 early-preterm, 31 late-preterm, 21 early-term, and 30 term births. The potential involvement of vitamin D in the regulation of inflammation was evaluated by Q-PCR in human uterine smooth muscle (UTSM) cell line.

RESULTS: Maternal 25-OH-D was lowest in early-preterm births (22.9 ± 4.2 ng/ml versus 34.4 ± 1.4 ng/ml; p = .029). Circulating CRH was high in early-preterm births (397 ± 30 pg/ml). Late-preterm (304 ± 13 pg/ml) and early-term births (347 ± 17 pg/ml) were not different from term births (367 ± 19 pg/ml), after accounting for gestational age. Maternal circulating 25-OH-D and CRH were not associated in term births. In preterm births, 25-OH-D below 30 ng/ml was associated with higher CRH. Vitamin D treatment of UTSM significantly reduced mRNA for leptin and IL-6 receptors. Deletion of vitamin D receptor from UTSM promoted the expression of the cox2 inflammatory marker.

CONCLUSION: Early-preterm birth showed a syndrome of high maternal CRH and low vitamin D status.