title: Estimated maternal ultraviolet B exposure levels in pregnancy influence skeletal development of the child.
abstract: BACKGROUND
  Relationships between vitamin D exposure of the mother in pregnancy and skeletal development of the child are poorly understood.
  
  
  OBJECTIVE
  Our objectives were to establish whether background UVB levels in the third trimester of pregnancy are related to bone mineral content (BMC) of the child, and to examine whether these relationships are explained by effects on height, fat, or lean mass.
  
  
  METHODS
  This was a prospective cohort study.
  
  
  METHODS
  The Avon Longitudinal Study of Parents and Children, a population-based birth cohort, was studied.
  
  
  METHODS
  A total of 6995 boys and girls with a mean age of 9.9 yr was studied.
  
  
  METHODS
  Prespecified analyses of relationships between background UVB levels in the third trimester of pregnancy, and total body less head BMC, bone area (BA), bone mineral density, and area-adjusted BMC as measured by dual-energy x-ray absorptiometry scans at 9.9 yr were performed.
  
  
  RESULTS
  Maternal UVB exposure was positively related to BMC (g) [9.6 (5.3, 13.8)], BA (cm(2)) [8.1 (4.3, 11.9)], and bone mineral density (g/cm(-2)) [0.003 (0.001, 0.004)], but not area-adjusted BMC (g) [0.69 (-0.22, 1.56)], suggesting an effect on bone size. Both height-dependent (cm) [0.18 (0.03, 0.32)] and height-independent (cm(2)) [4.1, (2.0, 6.2)] effects contributed to this association between UVB and BA. Although maternal UVB exposure was also related to lean mass (g) [163 (89, 237)], a positive association between UVB and BA persisted after adjusting for both height and lean mass [2.8 (1.0, 4.6)].
  
  
  CONCLUSIONS
  Maternal UVB exposure is related to bone size at age 9.9 yr independently of height and lean mass, suggesting that vitamin D status in pregnancy exerts direct effects on periosteal bone formation in subsequent childhood.
authors.affiliation: Academic Rheumatology, Department of Clinical Science at North Bristol, University of Bristol, Bristol BS2 8HW, United Kingdom. Jon.Tobias@bristol.ac.uk.
authors.forename: Adrian
authors.initials: A
authors.lastname: Sayers
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Tobias
mesh_terms: D015519:Bone Density / Q000528:radiation effects; D001846:Bone Development / Q000528:radiation effects*; D002648:Child; D015331:Cohort Studies; D005260:Female; D005333:Fetus / Q000528:radiation effects*; D006801:Humans; D016014:Linear Models; D008297:Male; D011247:Pregnancy; D011446:Prospective Studies; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000008:administration & dosage
chemical_list: D014807:Vitamin D