Changes in Umbilical Cord Blood Acid-Base Status after Delivery in Dependence on Time Intervall - A Continuing Forensic Problem

Background: The time window for measuring blood gases in the umbilical cord after birth is often discussed controversial with regard to birth damage claims. Methods: 53 umbilical cords from spontaneous deliveries at term were double clamped at room temperature directly after birth and paired arterial and venous samples were taken at 0,5, 10, 20, 40, 60 and 120 min. Arterial and venous blood gases [pH, pO(2), pCO(2), base-excess (BE)] were measured. Statistical analyses were performed with the t test and Wilcoxon test. Results: We measured data from (arterial/venous) pH 7.27 +/- 0.06 or, respectively, 7.34 +/- 0.06; BE 3.36 +/- 3.42 or, respectively, 3.64 +/- 2.58, pCO(2) 48.6 +/- 7.6 or, respectively, 38.6 +/- 6.4 mmHg (p < 0.001). The arterial and venous pH dropped significantly by 0.02 (p < 0.001) at 5 min. The arterial cord base excess dropped significantly to 2 mmol/L (p < 0.001) at 5 min. The venous cord base excess dropped slowly at 40 min. Arterial and venous pO(2) readings did not drop significantly, but the mean value showed variations. Arterial and venous pCO(2) values increased significantly within 40 or, respectively, 60 min. Actual literature reports differ dramatically in the increase or decrease of blood gas parameters. Discussion: Storage of the umbilical cord with room temperature results in changes in blood gas results within a short time of period. To avoid controversial discussion in civil court proceedings the blood gas probes from the umbilical cord should be analysed immediately after birth or stored in heparinised cooled syringes.