Abstract
Objective
Obtaining adequate vitamin D during pregnancy is important for the health of mother and child. Low circulating 25-hydroxyvitamin D (25OHD) concentrations, a measure of vitamin D status, have been reported in pregnant women in several countries; yet, there are few studies of pregnant Canadian women. We measured 25OHD concentrations in a multi-ethnic group of pregnant women living in Vancouver (49°N) and explored the determinants of 25OHD.
Methods
336 pregnant women (16-47 y) between 20 and 35 weeks gestation provided a blood sample and completed questionnaires.
Results
Mean 25OHD was 67 (95% CI 64-69) nmol/L. Only 1% of women had a 25OHD concentration indicative of severe deficiency (<25 nmol/L). However, 24% and 65% of women were vitamin D insufficient based on cut-offs of 50 and 75 nmol/L, respectively. In multivariate analysis, mean 25OHD concentrations were 12 nmol/L higher in the summer compared to in winter. Women of European (White) ethnicity had a 9-13 nmol/L higher mean 25OHD concentration than women from other ethnic groups. Almost 80% of women took vitamin D-containing supplements containing ≥400 IU/d. However, 24% and 65% of these women had 25OHD <50 and <75 nmol/L, respectively.
Conclusion
Vitamin D insufficiency was not uncommon in this group of pregnant women. Season and ethnicity were determinants of 25OHD but the magnitude of their effect was not large. Most women took vitamin D-containing supplements but this did not provide much protection against insufficiency. Consideration should be given to increasing the amount of vitamin D in prenatal supplements.
Résumé
Objectif
Des apports suffisants en vitamine D durant la grossesse sont importants pour la santé de la mère et de l’enfant. Dans plusieurs pays, on rapporte de faibles concentrations en 25-hydroxy-vitamine D (25OHD), une mesure du statut en vitamine D, dans le sang des femmes enceintes, mais il y a eu peu d’études sur le sujet auprès des Canadiennes enceintes. Nous avons mesuré les concentrations en 25OHD au sein d’un groupe multiethnique de femmes enceintes vivant à Vancouver (49 °N) et exploré les déterminants de la concentration en 25OHD.
Méthode
En tout, 336 femmes enceintes (de 16 à 47 ans) entre la 20e et la 35e semaine de gestation ont fourni un échantillon de sang et rempli des questionnaires.
Résultats
La concentration moyenne en 25OHD était de 67 nmol/L (IC de 95 % = 64-69). Seulement 1 % des femmes avaient une concentration en 25OHD indiquant un grave déficit (<25 nmol/L). Cependant, 24 % et 65 % des femmes, respectivement, étaient carencées en vitamine D selon que l’on place le point de coupure à 50 ou à 75 nmol/L. Dans une analyse multivariée, les concentrations moyennes en 25OHD étaient de 12 nmol/L de plus l’été que l’hiver. Les femmes d’origine ethnique européenne (blanche) avaient une concentration moyenne en 25OHD de 9 à 13 nmol/L de plus que les femmes d’autres groupes ethniques. Près de 80 % des femmes prenaient des suppléments contenant ≥400 UI/jour de vitamine D. Cependant, 24 % et 65 % de ces femmes, respectivement, avaient des concentrations en 25OHD de <50 et de <75 nmol/L.
Conclusion
Les carences en vitamine D n’étaient pas rares dans ce groupe de femmes enceintes. La saison et l’ethnicité étaient des déterminants des concentrations en 25OHD, mais l’ampleur de leur effet n’était pas importante. La plupart des femmes prenaient des suppléments contenant de la vitamine D, mais cela ne les protégeait pas beaucoup contre les carences. Il faudrait songer à accroître la quantité de vitamine D dans les suppléments nutritifs prénatals.
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Li, W., Green, T.J., Innis, S.M. et al. Suboptimal Vitamin D Levels in Pregnant Women Despite Supplement Use. Can J Public Health 102, 308–312 (2011). https://doi.org/10.1007/BF03404056
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DOI: https://doi.org/10.1007/BF03404056