title: Cord blood vitamin D and the risk of acute lower respiratory infection in Indigenous infants in the Northern Territory.
abstract: OBJECTIVE
  To assess vitamin D status in Indigenous mothers and infants in the Northern Territory, and to determine whether cord blood vitamin D levels are correlated with the risk of infant hospitalisation for acute lower respiratory infection (ALRI).
  
  
  METHODS
  Within a nested cohort of 109 Indigenous mother-infant pairs recruited between 2006 and 2011, we used liquid chromatography-mass spectrometry to measure vitamin D (25(OH)D3) levels in maternal blood during pregnancy (n = 33; median gestation, 32 weeks [range, 28-36 weeks]) and at birth (n = 106; median gestation, 39 weeks [range, 34-41 weeks]), in cord blood (n = 84; median gestation, 39 weeks [range, 36-41 weeks]), and in infant blood at age 7 months (n = 37; median age, 7.1 months [range, 6.6-8.1 months]).
  
  
  METHODS
  ALRI hospitalisations during the first 12 months of infancy, identified using International Classification of Diseases coding (J09-J22, A37-A37.9).
  
  
  RESULTS
  Compared with mean 25(OH)D3 levels in maternal blood during pregnancy (104 nmol/L), mean levels were 23% lower in maternal blood at birth (80 nmol/L) and 48% lower in cord blood samples (54 nmol/L). The mean cord blood 25(OH)D3 concentration in seven infants subsequently hospitalised for an ALRI was 37 nmol/L (95% CI, 25-48 nmol/L), lower than the 56 nmol/L (95% CI, 51-61 nmol/L) in the 77 infants who were not hospitalised with an ALRI (P = 0.025).
  
  
  CONCLUSIONS
  Cord blood 25(OH)D3 concentrations were about half those in maternal blood during the third trimester of pregnancy (about 7 weeks earlier). Most cord blood levels (80%) were classified as vitamin D insufficient (< 75 nmol/L) by existing guidelines, and were lower among infants who were subsequently hospitalised with an ALRI.
authors.affiliation: Menzies School of Health Research, Darwin, NT michael.binks@menzies.edu.au.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Binks
authors.affiliation: Menzies School of Health Research, Darwin, NT.
authors.forename: Heidi C
authors.initials: HC
authors.lastname: Smith-Vaughan
authors.affiliation: Menzies School of Health Research, Darwin, NT.
authors.forename: Robyn
authors.initials: R
authors.lastname: Marsh
authors.affiliation: Menzies School of Health Research, Darwin, NT.
authors.forename: Anne B
authors.initials: AB
authors.lastname: Chang
authors.affiliation: Menzies School of Health Research, Brisbane, QLD.
authors.forename: Ross M
authors.initials: RM
authors.lastname: Andrews
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D001315:Australia; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D009035:Mothers; D011247:Pregnancy; D012141:Respiratory Tract Infections / Q000097:blood* / Q000453:epidemiology*; D012307:Risk Factors; D014807:Vitamin D / Q000097:blood*; D014815:Vitamins / Q000097:blood*; D055815:Young Adult; D000095283:Australian Aboriginal and Torres Strait Islander Peoples
chemical_list: D014815:Vitamins; D014807:Vitamin D