Calcium and lactate in the fetal-to-neonatal transition

Objective To explore the relationship between calcium and lactate in arterial cord blood of healthy term neonates in response to the stress of labor. Methods This was a prospective cohort study of consecutive, vaginal, term births in a community medical center (April 2029 to February 2020). Calcium and lactate were measured in cord blood gas analysis immediately after delivery. Results In the arterial cord blood of 480 neonates, calcium levels were 1.5 (1.4; 1.5) mmol/L and lactate levels were 3.8 (2.9; 4.9) mmol/L. Calcium and lactate showed a statistically significant positive correlation (Pearson's correlation, r = 0.15, p = .001). Calcium levels had a significant positive correlation with PaCO2 and a significant negative correlation with pH, PaO2, HCO3-, and ABE levels. Multivariable analysis models confirmed that calcium levels were associated with HCO3-, gestational age, and birth weight, all accounting for 7% of the variability. Conclusion In healthy term vaginally delivered neonates, it was found that calcium and lactate were strongly correlated, together pointing to a neonatal response to the stress of labor and delivery. Cord blood calcium regulation may have an ancillary role in defining neonatal adaptation to extrauterine life.