title: The persistence of maternal vitamin D deficiency and insufficiency during pregnancy and lactation irrespective of season and supplementation.
abstract: BACKGROUND
  Pregnancy and lactation comprise a critical window spanning all seasons during which maternal vitamin D status potentially may influence the long-term health of the newborn. Women typically receive calcium/vitamin D supplementation through antenatal vitamins, but there has been limited serial evaluation of maternal vitamin D status across this critical window.
  
  
  METHODS
  In this prospective observational cohort study, 467 women in Toronto, Canada, underwent measurement of serum 25-hydroxy vitamin D (25-OH-D) at mean 29·7 ± 2·9 weeks' gestation, 3 months postpartum and 12 months postpartum, enabling serial assessment across 3 seasons. At each assessment, vitamin D status was classified as deficiency (25-OH-D<50 nmol/l), insufficiency (25-OH-D≥50 nmol/l and <75 nmol/l) or sufficiency (25-OH-D≥75 nmol/l).
  
  
  RESULTS
  The prevalence rates of vitamin D deficiency and insufficiency were 31·5% and 35·1% in pregnancy, 33·4% and 35·3% at 3 months, and 35·6% and 33·8% at 12 months postpartum, respectively. These high rates remained stable over time (P = 0·49) despite declining usage of antenatal calcium/vitamin D supplementation from pregnancy to 3 months to 12 months postpartum (P < 0·001). Indeed, on mixed model analyses, vitamin D deficiency and insufficiency in pregnancy were independently associated with decrements in average 25-OH-D over time of 49·6 nmol/l and 26·4 nmol/l, respectively (both P < 0·001). In contrast, season of baseline assessment and use of calcium/vitamin D supplements were independently associated with changes in 25-OH-D in the range of 3-5 nmol/l (both P < 0·008).
  
  
  CONCLUSIONS
  The persistence of vitamin D deficiency/insufficiency during pregnancy and lactation, irrespective of season and supplementation, supports the emerging concept that current vitamin D supplementation in antenatal care is likely inadequate.
authors.affiliation: Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto, ON, Canada.|Division of Endocrinology, University of Toronto, Toronto, ON, Canada.
authors.forename: Caroline K
authors.initials: CK
authors.lastname: Kramer
authors.affiliation: Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Chang
authors.initials: C
authors.lastname: Ye
authors.affiliation: Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Balakumar
authors.initials: B
authors.lastname: Swaminathan
authors.affiliation: Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto, ON, Canada.|Division of Endocrinology, University of Toronto, Toronto, ON, Canada.|Department of Nutritional Sciences, University of Toronto, Toronto, ON, Canada.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Hanley
authors.affiliation: Division of Endocrinology, University of Toronto, Toronto, ON, Canada.|Keenan Research Centre for Biomedical Science of St. Michael's Hospital, Toronto, ON, Canada.|Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
authors.forename: Philip W
authors.initials: PW
authors.lastname: Connelly
authors.affiliation: Division of Obstetrics and Gynecology, University of Toronto, Toronto, ON, Canada.
authors.forename: Mathew
authors.initials: M
authors.lastname: Sermer
authors.affiliation: Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto, ON, Canada.|Division of Endocrinology, University of Toronto, Toronto, ON, Canada.|Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Bernard
authors.initials: B
authors.lastname: Zinman
authors.affiliation: Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto, ON, Canada.|Division of Endocrinology, University of Toronto, Toronto, ON, Canada.|Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: Ravi
authors.initials: R
authors.lastname: Retnakaran
mesh_terms: D019587:Dietary Supplements; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007774:Lactation / Q000502:physiology*; D016014:Linear Models; D009864:Ontario / Q000453:epidemiology; D049590:Postpartum Period / Q000502:physiology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000188:drug therapy / Q000453:epidemiology / Q000503:physiopathology*; D015995:Prevalence; D011446:Prospective Studies; D012621:Seasons; D013997:Time Factors; D014807:Vitamin D / Q000008:administration & dosage* / Q000378:metabolism; D014808:Vitamin D Deficiency / Q000188:drug therapy / Q000453:epidemiology / Q000503:physiopathology*; D014815:Vitamins / Q000008:administration & dosage / Q000378:metabolism
chemical_list: D014815:Vitamins; D014807:Vitamin D