Delayed umbilical cord clamping at birth has effects on arterial and venous blood gases and lactate concentrations

Objective To estimate the influence of delayed umbilical cord clamping at birth on arterial and venous umbilical cord blood gases, bicarbonate (HCO3-), base excess (BE) and lactate in vigorous newborns. Setting University hospital. Design Prospective observational. Sample Vaginally delivered term newborns. Material and methods Umbilical cord arterial and venous blood was sampled repeatedly every 45 seconds (T-0 = time zero; T-45 = 45 seconds, T-90 = 90 seconds) until the cord pulsations spontaneously ceased in 66 vigorous singletons with cephalic vaginal delivery at 36-42 weeks. Longitudinal comparisons were performed with the Wilcoxon signed-ranks matched pairs test. Mixed effect models were used to describe the shape of the regression curves. Main outcome measures Longitudinal changes of umbilical cord blood gases and lactate. Results In arterial cord blood, there were significant decreases of pH (7.24-7.21), HCO3- (18.9-18.1 mmol/l) and BE (-4.85 to -6.14 mmol/l), and significant increases of PaCO2 (7.64-8.07 kPa), PO2 (2.30-2.74 kPa) and lactate (5.3-5.9 mmol/l) from T-0 to T-90, with the most pronounced changes at T-0-T-45. Similar changes occurred in venous blood pH (7.32-7.31), HCO3- (19.54-19.33 mmol/l), BE (-4.93 to-5.19 mmol/l), PaCO2 (5.69-5.81 kPa) and lactate (5.0-5.3 mmol/l), although the changes were smaller and most pronounced at T-45-T-90. No significant changes were observed in venous PO2. Conclusion Persistent cord pulsations and delayed cord clamping at birth result in significantly different measured values of cord blood acid-base parameters.