Correlation between calcium and phosphorus in cord blood and birth size in term infants.

Background: Calcium supplementation during pregnancy was suggested to affect fetal growth. We aimed to investigate the association between calcium and phosphorus in cord blood and birth size parameters in term infants.
Methods: The study included 70 pregnant women and their neonates. Birth weight, birth length and head circumference of the neonates were measured. Cord blood samples were obtained at delivery. Maternal and cord blood calcium, phosphorus and parathyroid hormone were measured. The association between variables was evaluated with Pearson correlation coefficient.
Results: Cord blood calcium levels were significantly positively correlated with birth weight, birth length and head circumference (r=0.308 P=0.009, r=0.324 P=0.006, r=0.296 P=0.013 respectively). Cord phosphorus was significantly positively correlated with birth length (r=0.358 P=0.002). In subjects with higher phosphorus levels cord calcium were more strongly correlated with birth weight, birth length and head circumference than in the overall group (r=0.487 P=0.003, r=0.515 P=0.002, r=0.396 P=0.018 respectively).
Conclusions: Cord blood calcium and phosphorus levels are associated with birth size parameters. There may be interactions between calcium and phosphorus to affect fetal growth.