Maternal arterial blood gas values during delivery: effect of mode of delivery, maternal characteristics, obstetric interventions and correlation to fetal umbilical cord blood.

INTRODUCTION Obstetricians routinely use biochemical parameters from non-pregnant women to assess the condition of the laboring mother. However, it is well known that pregnancy leads to significant physiological changes in most organ systems. The aim of this study was to determine normal values for maternal arterial blood gases during vaginal deliveries as compared to control values from planned cesarean sections. We also wanted to elucidate the effect of various maternal characteristics, mode of delivery and obstetric interventions on blood gas values. MATERIAL AND METHODS We carried out a randomly selected, prospective-observational cohort study of 250 women undergoing vaginal delivery and 58 women undergoing planned cesarean section at Department of Obstetrics and Gynecology, Skane University Hospital, Malmo, Sweden. RESULTS We found significant differences for gestational age, parity, umbilical venous blood pH, pCO2 and lactate values between the two study groups (P < 0.005). Significantly lower pH, pCO2 , pO2 , and sO2 were found in mothers delivering vaginally. Higher base deficit, hemoglobin, bilirubin, potassium, glucose and lactate were found in vaginal deliveries as compared to planned cesarean sections (P < 0.02). Maternal BMI, smoking and hypertension were not significantly correlated to acid base parameters in women with vaginal deliveries. On the other hand, multiple regression showed significant associations for the use of epidural anesthesia on maternal pH (P < 0.05) and pO2 (P < 0.01); and synthetic oxytocin on pCO2 (P = 0.08), glucose (P < 0.00) and lactate (P < 0.02) levels in maternal arterial blood. Maternal arterial pH, pCO2 and lactate values correlated significantly to values in venous umbilical cord blood (P < 0.000). CONCLUSIONS Maternal arterial blood gas parameters varied significantly according to mode of delivery, the use of epidural anesthesia and synthetic oxytocin.