Vitamin D status and intake in early school-aged children is tracking from pregnancy—the Swedish GraviD-Child study

Abstract Background The foetus depends on maternal vitamin D status during pregnancy, and the strong correlation between maternal and newborn vitamin D status is well established. However, the long-term tracking of vitamin D status and intake from pregnancy and to childhood remains largely unexplored. We aimed to evaluate vitamin D status and its determinants in early school-aged children, and to explore the tracking of vitamin D status and intake from pregnancy to childhood. Methods The Swedish GraviD-Child study includes data of vitamin D status and intake from the mothers first trimester of pregnancy to their children at age 8 years. Concentrations of 25-hydroxyvitamin D (25OHD) were analysed in the first and third trimesters and in children at age 8 years. Vitamin D intake from vitamin D-rich foods was reported in the third trimester, and in children at the ages 5 and 8 years. Candidate determinants of 25OHD concentrations in the children at age 8 years were collected through questionnaires and clinical assessments and analysed using multivariable linear regression. Associations between season-corrected 25OHD concentrations and vitamin D intake during pregnancy and childhood were investigated by Spearman correlations. Results Among the 145 children included in the analysis, the mean (SD) 25OHD concentration at age 8 was 67.8 (15.6) nmol/L, with the majority (91.7%) having levels ≥ 50 nmol/L. The only statistically significant determinant of 25OHD concentrations at age 8 were season of blood sampling, with sampling during May to October being associated with higher 25OHD concentrations (p < 0.001). Positive correlations were observed between season-corrected 25OHD concentrations in mothers first trimester and in children at age 8 (rho = 0.2, p = 0.022). Reported vitamin D intake in the third trimester was positively correlated with intake in children at ages 5 (rho = 0.21, p = 0.017) and 8 years (rho = 0.19, p = 0.04), with intake at age 5 also positively correlated with intake at age 8 (rho = 0.41, p < 0.001). Conclusion Among early school-aged children in Sweden with generally adequate vitamin D status, season is an important determinant. In addition, vitamin D status and intake seems to track from pregnancy to childhood. Trial registration (NCT05228925|| https://www.clinicaltrials.gov/ || Registration Date 2021–11-18).