Influence of maternal oxygen administration on the term fetus before labor

Thirty-two healthy pregnant women at term who were to undergo cesarean section following epidural anesthesia were randomly assigned to receive preoperatively, by face mask, room air or oxygen for more than 10 minutes. Patients were kept at a left lateral tilt position of 15° and were unaware which gas was administered. Oxygenation significantly increased (p < 0.05) maternal Po₂ to 283 mm Hg (SD 67). The cord vein Po₂ of the group receiving oxygen was 34 mm Hg (SD 6), significantly higher (p < 0.01) than the value of 26 mm Hg (SD 7) in the group receiving room air. The cord artery Po₂ of the oxygen group was also significantly higher (p < 0.05) at 20 mm Hg (SD 6) versus 15 mm Hg (SD 6). No other cord gas values were significantly different. There was no significant difference in the cord vein-artery Po₂ differential. There was no significant difference in the infants' hematocrits determined at 4 hours of age in the two groups. All infants were in excellent condition (1-minute Apgar score ≥8).