Maternal Vitamin D Insufficiency Early in Pregnancy Is Associated with Increased Risk of Preterm Birth in Ethnic Minority Women in Canada

J Nutr. 2017 Jun;147(6):1145-1151. doi: 10.3945/jn.116.241216. Epub 2017 Apr 19.


Background: Maternal vitamin D insufficiency (plasma 25-hydroxyvitamin D [25(OH)D] <75 nmol/L) may play a role in ethnic disparities in rates of preterm and spontaneous preterm births.Objective: We explored the relation between maternal plasma 25(OH)D concentration in the first trimester (8-14 wk of gestation) and the risk of preterm and spontaneous preterm births (<37 wk of gestation) by ethnicity.Methods: We designed a case-control study that included 120 cases of preterm birth (<37 wk of gestation) and 360 term controls (≥37 wk of gestation) of singleton pregnancies from the 3D cohort, a multicenter study in 2456 pregnant women in Quebec, Canada. Plasma 25(OH)D was measured by LC-mass spectrometry. We compared the distribution of vitamin D status between cases and controls for 8 ethnic minority subgroups. We explored the association between maternal plasma 25(OH)D concentration and preterm and spontaneous preterm births with the use of splines in logistic regression by ethnicity.Results: The distributions of maternal vitamin D status (<50, 50-75, and >75 nmol/L) were different in preterm and spontaneous preterm birth cases compared with controls but only in women of ethnic minority (P-trend = 0.003 and 0.024, respectively). Among ethnic subgroups, sub-Saharan Africans (P-trend = 0.030) and Arab-West Asians (P-trend = 0.045) showed an inverse relation between maternal vitamin D status and the risk of preterm birth. Maternal plasma 25(OH)D concentrations of 30 nmol/L were associated with 4.05 times the risk of preterm birth in the total ethnic minority population (95% CI: 1.16, 14.12; P = 0.028) relative to participants with a concentration of 75 nmol/L. In contrast, there was no such association among nonethnic women (OR: 0.94; 95% CI: 0.48, 1.82; P = 0.85). There was no association when we considered only spontaneous preterm births in the total ethnic minority population (OR: 1.75; 95% CI: 0.39, 7.79; P = 0.46).Conclusion: Vitamin D insufficiency is associated with an increased risk of preterm birth in ethnic minority women in Canada.

Keywords: ethnicity; pregnancy; preterm birth; spontaneous preterm birth; vitamin D.

Publication types

  • Multicenter Study

MeSH terms

  • Adult
  • Africa South of the Sahara
  • Arabs*
  • Asia, Western
  • Asian People*
  • Black People*
  • Case-Control Studies
  • Female
  • Gestational Age
  • Humans
  • Logistic Models
  • Minority Groups*
  • Odds Ratio
  • Pregnancy
  • Pregnancy Complications / blood
  • Pregnancy Complications / ethnology
  • Pregnancy Complications / etiology
  • Pregnancy Outcome*
  • Premature Birth / etiology*
  • Quebec
  • Vitamin D / analogs & derivatives
  • Vitamin D / blood
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / complications*
  • Vitamin D Deficiency / ethnology


  • Vitamin D
  • 25-hydroxyvitamin D

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