Background and aims Previous studies in newborns have found a positive association between adiposity and maternal and cord blood 25-hydroxy-vitamin D status (vit-D). It has been hypothesised that vit-D play a role in adipocyte metabolism and that this can be linked to obesity. Cord blood vit-D is closely associated with maternal vit-D concentration and is further affected by maternal obesity. The aim with our study was to examine the association between newborn cord blood vit-D and body composition where analyses were stratified by maternal pre-pregnancy obesity since this is a strong determinant of newborn body composition.

Methods Pre-pregnancy obese and normal weight mothers were included. Cord blood was collected at birth and newborn body composition was assessed using dual-energy X-ray absorptiometry within 48 h of birth. Sufficient cord blood and scans were obtained in 173(55%) mother-newborn dyads. Multiple linear regressions with vit-D was as a dependent variable were performed.

Results We included 41 pre-pregnancy normal weight-newborn dyads and 132 pre-pregnancy obese–newborn dyads. There was no difference in mean cord blood vit-D between offspring of normal weight and obese mothers (59.6 vs. 62.4 nmol/l (p = 0.64)). Vit-D was significantly associated with normal weight offspring body composition, positively with lean mass (p = 0.031) and inversely with fat% (p = 0.037) but was not associated with obese offspring body composition. See Table 1.

Conclusion We found an association between vit-D and newborn body composition in normal weight offspring. This implies that the effect of vit-D on newborn body composition may be determined by maternal weight.