Seasonal Variation of 25-Hydroxyvitamin D among non-Hispanic Black and White Pregnant Women from Three US Pregnancy Cohorts

Authors

  • Miguel Angel Luque-Fernandez,

    Corresponding author
    1. Department of Epidemiology, Harvard School of Public Health, Boston, MA
    • Correspondence:

      Miguel Angel Luque-Fernandez, Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA.

      E-mail: mluquefe@hsph.harvard.edu

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  • Bizu Gelaye,

    1. Department of Epidemiology, Harvard School of Public Health, Boston, MA
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  • Tyler VanderWeele,

    1. Department of Epidemiology, Harvard School of Public Health, Boston, MA
    2. Department of Epidemiology and Biostatistics, Harvard School of Public Health, Boston, MA
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  • Cynthia Ferre,

    1. Maternal and Infant Health Branch, Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA
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  • Anna Maria Siega-Riz,

    1. Department of Epidemiology, Gillings School of Global Public Health, the Carolina Population Center, University of North Carolina at Chapel Hill, Chapel Hill, NC
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  • Claudia Holzman,

    1. Department of Epidemiology and Biostatistics, College of Human Medicine, Michigan State University, East Lansing, MI
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  • Daniel A. Enquobahrie,

    1. Department of Epidemiology, University of Washington, School of Public Health, Seattle, WA
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  • Nancy Dole,

    1. Department of Epidemiology, Gillings School of Global Public Health, the Carolina Population Center, University of North Carolina at Chapel Hill, Chapel Hill, NC
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  • Michelle A. Williams

    1. Department of Epidemiology, Harvard School of Public Health, Boston, MA
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Abstract

Background

Vitamin D deficiency during pregnancy has been associated with increased risk of complications and adverse perinatal outcomes. We evaluated seasonal variation of 25-hydroxyvitamin D [25(OH)D] among pregnant women, focusing on patterns and determinants of variation.

Methods

Data came from three cohort studies in the US that included 2583 non-Hispanic Black and White women having prenatal 25(OH)D concentrations determined. Fourier time series and generalised linear models were used to estimate the magnitude of 25(OH)D seasonality. We modelled seasonal variability using a stationary cosinor model to estimate the phase shift, peak–trough difference, and annual mean of 25(OH)D.

Results

We observed a peak for 25(OH)D in summer, a nadir in winter, and a phase of 8 months, which resulted from fluctuations in 25(OH)D3 rather than 25(OH)D2. After adjustment for covariates, the annual mean concentrations and estimated peak–trough difference of 25(OH)D among Black women were 19.8 ng/mL [95% confidence interval (CI) 18.9, 20.5] and 5.8 ng/mL [95% CI 4.7, 6.7], and for non-Hispanic White women were 33.0 ng/mL [95% CI 32.6, 33.4] and 7.4 ng/mL [95% CI 6.0, 8.9].

Conclusions

Non-Hispanic Black women had lower average 25(OH)D concentrations throughout the year and smaller seasonal variation levels than non-Hispanic White women. This study's confirmation of 25(OH)D seasonality over a calendar year has the potential to enhance public health interventions targeted to improve maternal and perinatal outcomes.

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