Prospective audit of vitamin D levels of women presenting for their first antenatal visit at a tertiary centre

Vitamin D in preterm infants: A prospective observational study

AIM

Preterm infants are at increased risk of vitamin D deficiency as a result of both maternal deficiency and inadequate supplementation. The quantity and effectiveness of vitamin D supplementation in preterm infants are unclear. The aim of this study was to evaluate the natural history of vitamin D status in preterm infants and the effectiveness of the hospital's nutritional practices in meeting current supplementation recommendations.

METHODS

A prospective observational study was undertaken in the Neonatal Unit at the Women's and Children's Hospital, Adelaide. Enrolled infants received a standardised nutrition protocol with emphasis on vitamin D supplementation. The main outcome measure was a comparison of the proportion of vitamin D-deficient infants (25(OH)D < 50 nmol/L) at birth versus 36 weeks post-menstrual age/discharge.

RESULTS

Twenty-eight infants born between 30 and 36 weeks gestation were enrolled. The proportion of vitamin D-deficient infants decreased from initial to final measurement (32.1% vs. 7.1%, P = 0.016), whereas mean (standard deviation) 25(OH)D3 increased over the same period (58.4 (18.4) versus 82.9 (29.2) nmol/L, P < 0.001). Mean vitamin D intake was 643.6 (285.3) IU/day.

CONCLUSIONS

Current nutritional practices are effective in meeting recommendations regarding vitamin D intake and result in a lower proportion of deficient infants at 36 weeks post-menstrual age/discharge.

Vitamin D Receptor Gene Ablation in the Conceptus Has Limited Effects on Placental Morphology, Function and Pregnancy Outcome

Vitamin D deficiency has been implicated in the pathogenesis of several pregnancy complications attributed to impaired or abnormal placental function, but there are few clues indicating the mechanistic role of vitamin D in their pathogenesis. To further understand the role of vitamin D receptor (VDR)-mediated activity in placental function, we used heterozygous Vdr ablated C57Bl6 mice to assess fetal growth, morphological parameters and global gene expression in Vdr null placentae. Twelve Vdr^+/- dams were mated at 10–12 weeks of age with Vdr^+/- males. At day 18.5 of the 19.5 day gestation in our colony, females were euthanised and placental and fetal samples were collected, weighed and subsequently genotyped as either Vdr^+/+, Vdr^+/-or Vdr^-/-. Morphological assessment of placentae using immunohistochemistry was performed and RNA was extracted and subject to microarray analysis. This revealed 25 genes that were significantly differentially expressed between Vdr^+/+ and Vdr^-/- placentae. The greatest difference was a 6.47-fold change in expression of Cyp24a1 which was significantly lower in the Vdr^-/- placentae (P<0.01). Other differentially expressed genes in Vdr^-/- placentae included those involved in RNA modification (Snord123), autophagy (Atg4b), cytoskeletal modification (Shroom4), cell signalling (Plscr1, Pex5) and mammalian target of rapamycin (mTOR) signalling (Deptor and Prr5). Interrogation of the upstream sequence of differentially expressed genes identified that many contain putative vitamin D receptor elements (VDREs). Despite the gene expression differences, this did not contribute to any differences in overall placental morphology, nor was function affected as there was no difference in fetal growth as determined by fetal weight near term. Given our dams still expressed a functional VDR gene, our results suggest that cross-talk between the maternal decidua and the placenta, as well as maternal vitamin D status, may be more important in determining pregnancy outcome than conceptus expression of VDR.

Vitamin D in childhood and adolescence: an expert position statement

Vitamin D is a key hormone in the regulation of calcium and phosphorus metabolism and plays a pivotal role in bone health, particularly during pediatric age when nutritional rickets and impaired bone mass acquisition may occur. Great interest has been placed in recent years on vitamin D's extraskeletal actions. However, while recent data suggest a possible role of vitamin D in the pathogenesis of several pathological conditions, including infectious and autoimmune diseases, the actual impact of vitamin D status on the global health of children and adolescents, other than bone, remains a subject of debate. In the meantime, pediatricians still need to evaluate the determinants of vitamin D status and consider vitamin D supplementation in children and adolescents at risk of deficiency. This review is the result of an expert meeting that was held during the congress "Update on vitamin D and bone disease in childhood" convened in Pisa, Italy, in May 2013.

CONCLUSION

The collaboration of the international group of experts produced this "state of the art" review on vitamin D in childhood and adolescence. After dealing with vitamin D status and its determinants, the review outlines the current debate on vitamin D's health benefits, concluding with a practical approach to vitamin D supplementation during childhood and adolescence.

WHAT IS KNOWN

• Vitamin D deficiency is a worldwide health problem. • Vitamin D deficiency affects not only musculoskeletal health but also a potentially wide range of acute and chronic diseases. What is New: • We reviewed the literature focusing on randomized controlled trials of vitamin D supplementation during childhood and adolescence. • This review will help pediatricians to appreciate the clinical relevance of an adequate vitamin D status and it will provide a practical approach to vitamin D supplementation.

Vitamin D concentrations in pregnant women with diabetes attending for antenatal care in Far North Queensland

Serum concentrations of vitamin D were measured in 101 pregnant women with diabetes, both pre-existing and gestational, who attended for antenatal care in Cairns Base Hospital. Eighty-two (81.2%) had sufficient concentrations of vitamin D, 12 (11.9%) had levels indicating insufficiency and 7 (6.9%) were deficient. These findings contrast with those in the general population of pregnant women in the region, among whom 93.1% have been shown to have sufficient levels. The study contributes to the ongoing debate around the need for universal antenatal vitamin D screening in Australia.