Serum calcium normal range in 1000 term newborns.

Introduction: Serum calcium rapidly declines at birth because of the sudden interruption of the maternal-fetal calcium influx. Several factors are known to influence serum calcium in the first days of life, including circulating concentrations of maternal vitamin D. Objective was to establish the normal range variations of neonatal serum calcium according to the French current vitamin D supplementation during pregnancy, i.e. 100,000 IU of cholecalciferol during the third trimester.

Methods: We included in our prospective cohort study 1002 mother-newborn dyads from, with recruitments from April 2012 to July 2014 in France, in two recruiting centers located in Paris neighborhoods.

Results: Total serum calcium at 3 days of life in neonates varied from 2.06 to 2.73 mmol/L [2.5 and 97.5 percentiles], with a mean of 2.45 mmol/L. Serum calcium was similar between babies born from vitamin D supplemented mothers and those born from the non-supplemented ones. Univariate and multivariable analyses demonstrated the importance of maternal and cord blood 25(OH)D concentrations for newborn serum calcium maintenance.

Conclusion: We established that the expected serum calcium in neonates ranges between 2.06 and 2.73 mmol/L which is significantly wider than the adult range. This finding should help physicians in the diagnosis of hypo- or hypercalcemia. In addition, our study supports the importance of vitamin D supplementation and 25(OH)D status for neonatal serum calcium maintenance.