Longitudinal measures of maternal vitamin D and neonatal body composition

Vitamin D status has been associated with fetal growth and offspring's bone mass in some observational studies. We characterize the trajectory of total maternal serum 25-hydroxyvitamin D [25(OH)D] concentration by race and examine whether vitamin D status is associated with neonatal anthropometry and body composition as assessed by dual energy X-ray absorptiometry (DXA).

Three longitudinal pregnancy samples from the Memphis site of the Calcium for Preeclampsia Prevention trial (1992-1995) were used. Racial differences in total 25(OH)D trajectories (n = 343 women) were tested using an interaction term between blood draw gestational week and race in linear mixed-effects models. Linear regression and linear mixed-effects models estimated the adjusted associations between total 25(OH)D concentration with neonatal anthropometry and body composition (n = 252 with DXA) including interactions with infant sex and serum calcium.

Total 25(OH)D concentration increased with gestational age, but its trajectory over pregnancy did not differ between African-American and Caucasian women. Deficient maternal vitamin D (25(OH)D concentration <20 ng/ml) was associated with lower neonatal total bone mineral density (β -0.009 g/cm²; 95% CI -0.016, -0.002). Among male newborns, deficiency was also associated with lower lean mass (-217 g; -391, -43) and birthweight (-308 g; -540, -76). Deficient maternal vitamin D was also associated with lower ponderal index (β -2.3 kg/m³; 95% CI -4.0, -0.5) among those in the lowest calcium tertile.

Vitamin D deficiency during pregnancy is associated with lower bone density and smaller size at birth in certain subgroups suggesting its importance in fetal development.