High Pregnancy, Cord Blood and Infant Vitamin D Concentrations May Predict Slower Infant Growth.

Context: The relationship of maternal and infant 25-hydroxyvitamin D concentration [25(OH)D] with infant growth is unclear.

Objective: Our objective was to explore whether 25(OH)D in pregnancy, umbilical cord blood (UCB) or in infancy are associated with infant growth.

Design: This study involved 798 healthy infants and their mothers in Finland. We assessed 25(OH)D during pregnancy, from UCB at birth and from the infant at the age of 12 months.

Main Outcome Measures: Infant length, weight, length-adjusted weight, head circumference at 6 and 12 months and mid-upper-arm circumference at 12 months.

Results: Of the mothers and infants 96% and 99% were vitamin D sufficient [25(OH)D ≥50 nmol/L]. Mothers with pregnancy 25(OH)D >125 nmol/L had the shortest, lightest (in weight) and thinnest (in length-adjusted weight) infants at 6 months (P for all <0.05). For each 10 nmol/L higher UCB 25(OH)D, the infants were 0.03 standard deviation score (SDS) shorter at 6 months (95% confidence interval -0.05, -0.01), adjusted for birth size, infant 25(OH)D and parental height. Higher UCB 25(OH)D associated with smaller head circumference at 6 and 12 months (P for all <0.05) but attenuated after adjustments. Mothers with pregnancy 25(OH)D >125 nmol/L had the thinnest infants at 12 months (P=0.021). For each 10 nmol/L higher infant 25(OH)D, the infants were 0.03 SDS lighter (-0.05, -0.01) and 0.03 SDS thinner (-0.05, 0.00) at 12 months.

Conclusions: Our results suggest that high pregnancy, cord blood and infant vitamin D concentration may have disadvantageous effects on infant growth.