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

Objective To determine a reference interval for maternal arterial blood values during vaginal delivery and to elucidate the effect of common maternal characteristics and obstetric interventions on maternal acid base values during vaginal and planned cesarean section (CS). Design Prospective, observational study of randomly selected women undergoing vaginal deliveries and planned CS at Skane University Hospital, Malmo, Sweden. Results Two hundred and fifty women undergoing vaginal delivery (VD) and fifty-eight women undergoing planned CS were recruited. We found significant differences for gestational age, parity, artery pH, pCO 2 , pO 2 , sO 2 and cord venous pH, pCO 2 and lactate between the two study groups ( P < 0.005). For women undergoing vaginal delivery, we found significant changes in base deficit, hemoglobin, bilirubin, potassium, glucose and lactate values as compared to women with planned CS ( P < 0.02). Maternal characteristics did not significantly affect acid base parameters however, multiple regression showed significant associations for the use of epidural anesthesia on maternal pH ( P < 0.05) and pO 2 ( P < 0.01); and synthetic oxytocin on pCO 2 ( P = 0.08), glucose ( P < 0.00) and lactate ( P < 0.02) in maternal blood. Maternal arterial pH, pCO 2 and lactate correlated significantly to values in venous umbilical cord blood ( P < 0.000). Conclusions Reference values for maternal arterial blood gases in vaginal deliveries for term pregnancies were outlined and we found that most arterial blood gas parameters varied significantly according to mode of delivery. The use of different obstetrical interventions like epidural anesthesia or synthetic oxytocin, resulted in significant changes in blood gas values.