title: Vitamin D Status and Gestational Diabetes: Effect of Smoking Status during Pregnancy.
abstract: BACKGROUND
  Vitamin D status, as measured by serum 25-hydroxyvitamin D (25(OH)D), has been shown in some studies to be inversely associated with gestational diabetes risk. Recently, it has been suggested that maternal smoking status may modify this relationship. We explored the association between 25(OH)D concentration and gestational diabetes and determined if there was an interaction between smoking and 25(OH)D.
  
  
  METHODS
  A nested case-control study was conducted in Halifax, Nova Scotia and Quebec City, Quebec. Women were recruited before 20 weeks gestation and 25(OH)D was measured. Cases were women who developed gestational diabetes and controls were frequency matched to cases on study site, gestational age at blood draw, and season and year of blood draw. Logistic regression models estimated adjusted odds ratios (aOR) and 95% confidence intervals (CI). Models were tested for multiplicative and additive interaction, which was estimated by relative excess risk due to interaction (RERI).
  
  
  RESULTS
  The study included 395 gestational diabetes cases and 1925 controls. Women who smoked during pregnancy and had 25(OH)D concentrations <30 nmol/L had an aOR = 3.73 [95% CI 1.95, 7.14] compared to non-smokers with 25(OH)D concentrations ≥50 nmol/L. Additive interaction was detected between smoking status and 25(OH)D [RERI = 2.44, 95% CI 0.03, 4.85].
  
  
  CONCLUSIONS
  Our study supports the inverse association of vitamin D status with gestational diabetes risk, particularly among women who smoke during pregnancy. More research is needed to confirm this finding and, if confirmed, to determine the mechanism by which the combined effect of smoking and low vitamin D status increases the risk of developing gestational diabetes.
authors: Perinatal Epidemiology Research Unit, Departments of Obstetrics & Gynaecology and Pediatrics, Dalhousie University and IWK Health Centre, Halifax, NS, Canada.
authors: Linda
authors: L
authors: Dodds
authors: Perinatal Epidemiology Research Unit, Departments of Obstetrics & Gynaecology and Pediatrics, Dalhousie University and IWK Health Centre, Halifax, NS, Canada.
authors: Christy G
authors: CG
authors: Woolcott
authors: School of Dietetics and Human Nutrition, McGill University, Sainte-Anne-de-Bellevue, QC, Canada.
authors: Hope
authors: H
authors: Weiler
authors: Perinatal Epidemiology Research Unit, Departments of Obstetrics & Gynaecology and Pediatrics, Dalhousie University and IWK Health Centre, Halifax, NS, Canada.
authors: Anne
authors: A
authors: Spencer
authors: Department of Molecular Biology, Medical Biochemistry and Pathology, CHU de Québec Research Centre, Université Laval, Quebec City, QC, Canada.
authors: Jean-Claude
authors: JC
authors: Forest
authors: Department of Obstetrics & Gynaecology, Dalhousie University and IWK Health Centre, Halifax, NS, Canada.
authors: B Anthony
authors: BA
authors: Armson
authors: Department of Molecular Biology, Medical Biochemistry and Pathology, CHU de Québec Research Centre, Université Laval, Quebec City, QC, Canada.
authors: Yves
authors: Y
authors: Giguère
mesh_terms: D000328:Adult; D016640:Diabetes, Gestational / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D007231:Infant, Newborn; D008425:Maternal Behavior; D009674:Nova Scotia / Q000453:epidemiology; D016017:Odds Ratio; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood / Q000209:etiology*; D011261:Pregnancy Trimester, First; D037841:Pregnant People; D011297:Prenatal Exposure Delayed Effects / Q000097:blood / Q000453:epidemiology*; D011792:Quebec / Q000453:epidemiology; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects / Q000097:blood / Q000453:epidemiology*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications* / Q000453:epidemiology; D014815:Vitamins / Q000627:therapeutic use
chemical_list: D014815:Vitamins; D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: 25-hyroxyvitamin D; gestational diabetes; pregnancy; smoking