Maternal vitamin D status affects bone growth in early childhood—a prospective cohort study

Design: prospective observational cohort. Participants: 87 children followed from birth to 14 months; originally 124 families recruited; two groups defined by maternal S-25-OHD during pregnancy (Low D vs High D) using a median split at 42.6 nmol/L. Mothers were healthy, non-smoking, aged 20–40, Caucasian; singleton full-term pregnancies. Bone outcomes measured by peripheral quantitative computed tomography (pQCT) of the left tibia at 14 months; serum 25-OHD and bone turnover markers; dietary intake recorded with a 3-day food record; all infants received vitamin D supplementation; ethics approval obtained.

Postnatal vitamin D supplementation improved vitamin D status but did not fully offset prenatal vitamin D effects on bone development. At 14 months, serum 25-OHD was similar between Low D and High D groups (63 vs 66 nmol/L, p=0.58). Total vitamin D intake was similar (~12.3 μg/day). In Low D, tibial BMC at birth was lower but gain by 14 months was greater, yielding similar BMC between groups; High D had higher tibial CSA at baseline that persisted at 14 months (p=0.068). BMD and ΔBMD were similar. Approximately 20% of infants had S-25-OHD <50 nmol/L at 14 months despite adequate intake; higher vitamin D intake may be advisable. Conclusion: Ensuring adequate vitamin D during pregnancy is important, as fetal vitamin D status partly shapes bone growth across infancy; postnatal supplementation partially mitigates effects but cannot fully reverse them.

70% follow-up at 14 months; 78% success rate for pQCT measurements; limited sample size and statistical power; observational design with potential confounding and selection bias; measurements limited to total bone parameters at a single tibial site; not all relevant factors (e.g., IGF-1) were assessed; small number of Vitamin D3 users; limited generalizability.