The purpose of this study is to investigate the relationship of creatine kinase (CK) and its isoenzyme levels in the newborn to the mode of delivery, time interval from birth (divided in four 6-hour time periods), parity and sex of the neonates. During the 1st postpartum day, serum levels of CK and its isoenzymes (CK-MM, CK-MB, CK-BB) were determined from 115 healthy full-term neonates born consecutively either by spontaneous vaginal delivery (VD, n = 85) or by elective cesarean section (CS, n = 30). The multiple regression analysis was applied. Total CK levels were positively correlated with VD (p < 0.0003). This was mainly attributed to a rise in the CK-MM activity which presented a similar pattern to CK. CK-MB activity was also positively correlated with VD. In contrast, CK-BB was negatively correlated to the postpartum time period. Neonatal sex and parity did not influence CK and its isoenzyme levels significantly. In conclusion, VD contributes significantly to an increase in CK levels during the 1st day of extrauterine life.