title: Changes in plasma concentrations of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D during pregnancy: a Brazilian cohort.
abstract: OBJECTIVE
  To characterize the physiological changes in 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] throughout pregnancy.
  
  
  METHODS
  Prospective cohort of 229 apparently healthy pregnant women followed at 5th-13th, 20th-26th, and 30th-36th gestational weeks. 25(OH)D and 1,25(OH)2D concentrations were measured by LC-MS/MS. Statistical analyses included longitudinal linear mixed-effects models adjusted for parity, season, education, self-reported skin color, and pre-pregnancy BMI. Vitamin D status was defined based on 25(OH)D concentrations according to the Endocrine Society Practice Guideline and Institute of Medicine (IOM) for adults.
  
  
  RESULTS
  The prevalence of 25(OH)D <75 nmol/L was 70.4, 41.0, and 33.9%; the prevalence of 25(OH)D <50 nmol/L was 16.1, 11.2, and 10.2%; and the prevalence of 25(OH)D <30 nmol/L was 2, 0, and 0.6%, at the first, second, and third trimesters, respectively. Unadjusted analysis showed an increase in 25(OH)D (β = 0.869; 95% CI 0.723-1.014; P < 0.001) and 1,25(OH)2D (β = 3.878; 95% CI 3.136-4.620; P < 0.001) throughout pregnancy. Multiple adjusted analyses showed that women who started the study in winter (P < 0.001), spring (P < 0.001), or autumn (P = 0.028) presented a longitudinal increase in 25(OH)D concentrations, while women that started during summer did not. Increase of 1,25(OH)2D concentrations over time in women with insufficient vitamin D (50-75 nmol/L) at baseline was higher compared to women with sufficient vitamin D (≥75 nmol/L) (P = 0.006).
  
  
  CONCLUSIONS
  The prevalence of vitamin D inadequacy varied significantly according to the adopted criteria. There was a seasonal variation of 25(OH)D during pregnancy. The women with insufficient vitamin D status present greater longitudinal increases in the concentrations of 1,25(OH)2D in comparison to women with sufficiency.
authors.affiliation: Nutritional Epidemiology Observatory, Josué de Castro Nutrition Institute, Rio de Janeiro Federal University, Avenida Carlos Chagas Filho, 373, CCS, Bloco J, 2° andar, Cidade Universitária-Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil.
authors.forename: Amanda C Cunha
authors.initials: ACC
authors.lastname: Figueiredo
authors.affiliation: Nutritional Epidemiology Observatory, Josué de Castro Nutrition Institute, Rio de Janeiro Federal University, Avenida Carlos Chagas Filho, 373, CCS, Bloco J, 2° andar, Cidade Universitária-Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil.
authors.forename: Paula Guedes
authors.initials: PG
authors.lastname: Cocate
authors.affiliation: Division of Nutrition, Food and Public Health, Department of Life Science, University of Westminster, London, UK.
authors.forename: Amanda R Amorim
authors.initials: ARA
authors.lastname: Adegboye
authors.affiliation: Nutritional Epidemiology Observatory, Josué de Castro Nutrition Institute, Rio de Janeiro Federal University, Avenida Carlos Chagas Filho, 373, CCS, Bloco J, 2° andar, Cidade Universitária-Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil.|Department of Social Nutrition, Emília de Jesus Ferreira Nutrition School, Fluminense Federal University, Niteroi, Brazil.
authors.forename: Ana Beatriz
authors.initials: AB
authors.lastname: Franco-Sena
authors.affiliation: Nutritional Epidemiology Observatory, Josué de Castro Nutrition Institute, Rio de Janeiro Federal University, Avenida Carlos Chagas Filho, 373, CCS, Bloco J, 2° andar, Cidade Universitária-Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil.|Graduate Program in Nutrition, Josué de Castro Nutrition Institute, Rio de Janeiro Federal University, Rio de Janeiro, Brazil.
authors.forename: Dayana R
authors.initials: DR
authors.lastname: Farias
authors.affiliation: Nutritional Epidemiology Observatory, Josué de Castro Nutrition Institute, Rio de Janeiro Federal University, Avenida Carlos Chagas Filho, 373, CCS, Bloco J, 2° andar, Cidade Universitária-Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil.|Graduate Program in Nutrition, Josué de Castro Nutrition Institute, Rio de Janeiro Federal University, Rio de Janeiro, Brazil.
authors.forename: Maria Beatriz Trindade
authors.initials: MBT
authors.lastname: de Castro
authors.affiliation: USDA, ARS, Western Human Nutrition Research Center, University of California, Davis, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Brito
authors.affiliation: USDA, ARS, Western Human Nutrition Research Center, University of California, Davis, USA.
authors.forename: Lindsay H
authors.initials: LH
authors.lastname: Allen
authors.affiliation: School of Medicine, Boston University , Boston, USA.
authors.forename: Rana R
authors.initials: RR
authors.lastname: Mokhtar
authors.affiliation: School of Medicine, Boston University , Boston, USA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Holick
authors.affiliation: Nutritional Epidemiology Observatory, Josué de Castro Nutrition Institute, Rio de Janeiro Federal University, Avenida Carlos Chagas Filho, 373, CCS, Bloco J, 2° andar, Cidade Universitária-Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil. gilberto.kac@gmail.com.|Graduate Program in Nutrition, Josué de Castro Nutrition Institute, Rio de Janeiro Federal University, Rio de Janeiro, Brazil. gilberto.kac@gmail.com.
authors.forename: Gilberto
authors.identifier: http://orcid.org/0000-0001-8603-9077
authors.initials: G
authors.lastname: Kac
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood*; D000328:Adult; D001938:Brazil / Q000453:epidemiology; D002112:Calcifediol / Q000097:blood*; D002117:Calcitriol / Q000097:blood*; D015331:Cohort Studies; D004032:Diet / Q000009:adverse effects; D019587:Dietary Supplements; D004872:Ergocalciferols / Q000097:blood*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D039382:Maternal Nutritional Physiological Phenomena; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood* / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D015995:Prevalence; D011446:Prospective Studies; D012621:Seasons; D057566:Self Report; D014807:Vitamin D / Q000008:administration & dosage / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000097:blood* / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D055815:Young Adult
chemical_list: D004872:Ergocalciferols; D014807:Vitamin D; D015652:25-Hydroxyvitamin D 2; C003564:1,25-dihydroxyergocalciferol; D002117:Calcitriol; D002112:Calcifediol
keywords: Cohort; Micronutrients; Pregnancy; Seasons; Tropical country; Vitamin D