Nonlinear and sex-specific associations of maternal vitamin D in early- and mid-pregnancy with childhood growth trajectories from birth to 6 years of age: a prospective cohort study in China.

OBJECTIVES

To examine the associations of maternal vitamin D (VitD) concentrations in early- and mid-pregnancy with offspring growth trajectories from birth to 6 years of age, as well as childhood overweight.

METHODS

This study was a prospective observational cohort study including 1,100 mother-child dyads from the Wuxi Birth Cohort. Offspring weight-, height-, and BMI-for-age Z-scores (WAZ, HAZ, and BAZ) were collected from birth to 6 years of age. Growth trajectories were identified using group-based trajectory modeling (GBTM). Restricted cubic spline (RCS) analyses explored the nonlinear associations. Multivariable logistic regression was used to assess associations of maternal VitD tertiles (T1-T3) with growth trajectory groups and overweight risk, with exploratory analyses stratified by child sex.

RESULTS

Lower early pregnancy VitD concentrations (T1 vs. T2) were associated with higher odds of increasing HAZ (aOR, 1.84; 95% CI, 1.16, 2.92) and BAZ (aOR, 1.63; 95% CI, 1.09, 2.43) trajectories. Lower mid-pregnancy VitD concentrations were associated with higher odds of increasing WAZ (aOR, 3.21; 95% CI, 1.41, 7.34) and HAZ (aOR, 1.94; 95% CI, 1.03, 3.66) trajectories. Higher early pregnancy VitD concentrations (T3 vs. T2) were associated with higher odds of increasing BAZ, particularly among boys (aOR, 2.11; 95% CI, 1.16, 3.82). Sex-stratified analyses suggested stronger associations for WAZ- and BAZ-related trajectories in boys and HAZ-related trajectories in girls. RCS analyses showed nonlinear associations, with the lowest odds of adverse trajectories observed at 27.6-72.6 nmol/L in early pregnancy and 28.8-76.2 nmol/L in mid-pregnancy. Overweight at age 6 was nearly ten times more common in children with increasing vs. stable BAZ trajectories.

CONCLUSION

Maternal VitD levels in early- and mid-pregnancy showed nonlinear and sex-specific associations with offspring growth trajectories. Both low and high maternal VitD levels during these gestational periods were associated with higher odds of unstable growth trajectories.