Background: Vitamin D deficiency in children clinically manifests as rickets causing growth impairment and bowing of the long bones, potentially increasing the ratio between crown-rump length and length (CRL:L) or sitting height and height (SH:H).
Objective and hypotheses: We investigated whether CRL:L in 19-months-olds and SH:H in 36-months-olds were lower with higher cord 25hydroxyvitamin D (25OHD).
Method: Participants were included from the population-based prospective mother-child cohort, Odense Child Cohort, with inclusion of healthy singletons with available 25OHD and CRL:L or SH:H measures. Multiple linear regression was stratified by sex a priori and adjusted for pre-pregnancy body mass index, smoking during pregnancy, maternal ethnicity, season of blood sampling and child age. Postnatal adjustment included vitamin D supplementation and duration of exclusive breastfeeding.
Results: We included 520 participants (239 girls, 281 boys) at 19 months; and 989 children at 36 months (468 girls, 521 boys). Median (IQR) cord 25OHD was 48 (34.062.4) nmol/l. With every 10 nmol/l increase in cord 25OHD in boys, CRL:L increased 0.0008 (P=0.03) and SH:H increased 0.0004 (trend, P=0.07). Boys with cord 25OHD in Q4 had a 0.005 higher CRL:L (P=0.02) and a 0.003 higher SH:H (P=0.002) than boys in Q1. Post hoc regressions showed that sub-ischial leg length decreased 0.1 cm with each 10 nmol/l increase in 25OHD (P=0.002, 19 months and P=0.01, 36 months). Adjustment for duration of exclusive breastfeeding eliminated the association between 25OHD and CRL:L while a trend remained in SH:H (0.0000, P=0.07). No such associations were found in girls.
Conclusion: While cord 25OHD associated with longitudinal growth in boys, adjustment for breastfeeding eliminated this association at 19 months. Sex-specific patterns deserve further investigation.
10 Sep 2016 - 12 Sep 2016