Gestational Vitamin D3 Supplementation and Sun Exposure Significantly Influence Cord Blood Vitamin D Status and 3-Epi-25-Hydroxyvitamin D3 Levels in Term Newborns

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