Relationship between mode of delivery and neonatal calcium homeostasis.

Serum levels of calcium (Ca), calcitonin (CT) and parathyroid hormone (PTH) were determined in cord blood of 229 newborns. In 136 newborns the tests were repeated 24 h later. The probands were divided into four groups according to mode of delivery: (1) spontaneous; (2) elective caesarean section without labour; (3) elective caesarean section in labour; (4) emergency caesarean section with fetal distress. Newborns in group 2 had significantly lower Ca and CT levels and significantly higher PTH concentrations in cord blood than the other three groups. In all groups Ca and PTH concentrations were negatively correlated. At 24 h, mean Ca levels had decreased and mean CT and PTH concentrations had increased in all four groups. Newborns in group 2 still had lower Ca levels but higher CT and PTH concentrations. At that time there were negative correlations between Ca and CT levels in groups 1 and 2 and between Ca and PTH concentrations in group 1. These data demonstrate that without labour, cord blood Ca and CT levels are lower and PTH concentrations are higher. The low 24 h calcium in newborns delivered without labour is explained by the lower Ca levels at birth and a tremendous increase of CT. The PTH secretion in full-term newborns is very substantial and negatively correlated with Ca levels.