Gestational vitamin D3 supplementation and sun exposure significantly influence cord blood vitamin D status and 3-epi-25-hydroxyvitamin D3 levels in term newborns

Abstract

Background and aims: High prevalence of hypovitaminosis D is worldwide reported among pregnant women and newborns. We assessed cord blood 25-hydroxyvitamin D₃ [25(OH)D₃] and 3-epi-25-hydroxyvitamin D₃ (C₃-epimer) levels in relation to assumed maternal risk factors for hypovitaminosis D.

Methods: We enrolled 246 term newborns during summer. 175/246 mothers were supplemented with a daily variable dosage (200-1,000 IU) of vitamin D₃ during pregnancy. Cord blood 25(OH)D₃ and C₃-epimer concentrations were analyzed by high performance liquid chromatography tandem mass spectrometry.

Results: Median cord blood 25(OH)D₃ levels were 23.4 ng/mL (16.9-28.8). The prevalences of vitamin D sufficiency (≥ 30.0 ng/mL), insufficiency (20.0-29.9 ng/mL), and deficiency (< 20.0 ng/mL) were 19.9%, 45.9%, and 34.2%, respectively. Non-Caucasian ethnicity, housewife life, weight excess, negligible sun exposure and absent gestational vitamin D supplementation were associated with both reduced cord blood 25(OH)D₃ and C₃-epimer levels. C₃-epimer/25(OH)D₃ ratio was 15.1% (13.6%-18.4%) and it was not related to any of the assumed risk factors for hypovitaminosis D.

Conclusions: Cord blood vitamin D deficiency was common, particularly in newborns from mother not receiving vitamin D supplementation and with poor sun exposure. C₃-epimer levels were high in cord blood, causing possible misclassification of vitamin D status if they were not distinguished from 25(OH)D₃ concentrations.

Keywords: 3-epi-25-hydroxyvitamin D3; Cord blood; Sun exposure; Supplementation; Vitamin D.