The effect of maternal oxygen administration during the second stage of labor on umbilical cord blood gas values: A randomized controlled prospective trial

OBJECTIVE: Our aim was to determine whether supplemental oxygen during the second stage of normal labor affects cord blood gas and cooximetry values. STUDY DESIGN: Patients at term pregnancy were prospectively randomized to the control or treatment group at the onset of the second stage of labor. The treatment group received 10 L/min oxygen by face mask, which result in a mean fractional inspired oxygen concentration of 0.81. RESULTS: There were 86 patients randomized into the study. In the oxygen group there were significantly more cord arterial pH values < 7.20 (9/41 vs. 2/44, p< 0.05). The control group was compared with two subgroups of patients receiving oxygen: those receiving oxygen therapy for ≤ 10 minutes and those receiving oxygen for>10 minutes. Analysis of variance demonstrated significant differences (7.285 ± 0.058, 7.312 ± 0.056, 7.237 ± 0.064; F test 8.3, p = 0.0005). Among several independent vriables, regression analysis demonstrated that only duration of oxygen therapy had a significant inverse relation to cord arterialpH (F test = 15.6, p = 0.0002). CONCLUSIONS: Prolonged oxygen treatment during the second stage of normal labor resulted in a deterioration of cord blood gas values at birth.