Maternal vitamin D intake and BMI during pregnancy in relation to child’s growth and weight status from birth to 8 years: a large national cohort study

Objectives To examine the associations between maternal vitamin D intake and childhood growth and risk of overweight up to 8 years. We further examined the effect modification by maternal prepregnancy body mass index (BMI). Design Prospective population-based pregnancy cohort study. Setting The Norwegian Mother, Father and Child Cohort Study. Participants In total, 58 724 mothers and 66 840 singleton children, with information on maternal vitamin D intake during the pregnancy and minimum one postnatal anthropometric measurement. Outcome measures Predicted weight and height growth trajectories and velocities from 1 month to 8 years, rapid growth during infancy and toddlerhood, and risk of overweight in preschool and school age. Results Overall, maternal vitamin D intake was associated with lower weight trajectory, lower odds of rapid weight growth and higher odds of childhood overweight. In children of mothers with prepregnancy normal weight, maternal vitamin D intake was negatively associated with weight trajectory and lower OR of a rapid weight growth during the first year, compared with reference (<5 µg/day). Children of mothers with normal weight, with maternal vitamin D intakes of 10–15 and >15 µg/day, also had 0.86 (95% CI 0.77 to 0.97) and 0.88 (95% CI 0.79 to 0.99) lower odds for overweight at 3 years, compared with reference. In contrast, in children of mothers with prepregnancy overweight (BMI ≥25 kg/m2), vitamin D intake was positively associated with weight trajectory. Children of mothers with overweight, with maternal vitamin D intake of 5–9.9 µg/day, also had (1.09 (95% CI 1.01 to 1.18) and 1.12 (95% CI 1.02 to 1.23)) higher odds for overweight at 5 years and 8 years, compared with reference. Conclusions Maternal vitamin D intake affects postnatal growth and is inversely associated with childhood overweight in children of mothers with normal weight. Associations between maternal vitamin D intake and child growth and risk of overweight varied by prepregnancy BMI.


Supplementary table 2. Cut-offs of overweight in children
.00064.x b All children with a body mass index equal to, or above, the cut-off are denoted as overweight c Based on child´s body mass index calculated from the predicted anthropometric data.
BMJ Publishing Group Limited (BMJ) disclaims all liability and responsibility arising from any reliance Supplemental material placed on this supplemental material which has been supplied by the author(s) BMJ Open doi: 10.1136/bmjopen-2021-048980 :e048980.

Supplementary table 3.
Associations between maternal vitamin D intake from foods alone, and from supplements alone, and predicted weight growth trajectories from 1 month to 2 years of age.

Weight (in g)
All mothers (n=1216) Effect estimates derived by multilevel mixed effects linear regression model, adjusted for maternal education, parity, maternal milk and yoghurt intake, maternal fiber intake, child´s gender and birth weight. The model with all mothers was also adjusted for maternal pre-pregnancy BMI. The siblings in the lower maternal vitamin D category was used as reference in separate analyses of overall (n=1211), mothers with normal weight (n=845) and with overweight (n=320). a Mothers with pre-pregnancy BMI 18.5-24.9 kg/m 2 b Mothers with pre-pregnancy BMI ≥25 kg/m 2 BMJ Publishing Group Limited (BMJ) disclaims all liability and responsibility arising from any reliance

Supplementary table 8. Associations between total maternal vitamin D intake and predicted weight growth velocities and height growth
velocities from 1 month to 2 years of age.