Questioning the adequacy of standardized vitamin D supplementation protocol in very low birth weight infants: a prospective cohort study

Abstract

Abstract Objectives Preterm infants are at increased risk for vitamin D deficiency (VDD). We aimed to assess the adequacy of standardized vitamin D supplementation protocol in very low birth weight (VLBW) infants. Additionally, vitamin D status of mother/infant couples and the associations between vitamin D status at birth and morbidities of the infants were investigated. Methods In this single-center, prospective cohort study blood samples were collected from 55 mothers just before delivery and from their infants at birth and on the 30th day of life (DOL) for 25 hydroxy vitamin D (25OHD) measurements. Vitamin D was initiated in dose of 160 IU/kg by parenteral nutrition on the first DOL and oral vitamin D supplementation (400 IU/day) was administered when enteral feedings reached 50% of total intake or on the 15th DOL. Results The median 25OHD levels of the infants were 16.12 (9.14–20.50) in cord blood and 36.32 (31.10–44.44) in venous blood on the 30th DOL (p<0.01). In 98% of the VLBW infants 25OHD reached sufficient levels on the 30th DOL. None of the mothers had sufficient vitamin D levels (25OHD >30 ng/mL). Maternal 25OHD levels were correlated with the 25OHD levels of the infants in cord blood (r=0.665, p<0.001). There was a significant difference in mean cord 25OHD levels between winter (13.65 ± 5.69 ng/mL) and summer seasons (19.58 ± 11.67 ng/mL) (p=0.021). No association was found between neonatal morbidity and vitamin D status. Conclusions The results clearly show that by utilizing the current supplementation protocol, the majority of VLBW infants with deficient/insufficient serum 25OHD levels reached sufficient levels on the 30th DOL. Furthermore, vitamin D levels in mother/infant couples were found to be highly correlated.