Fetal oxygen saturation and fractional extraction at birth and the relationship to measures of acidosis

Measures of umbilical cord oxygen levels at birth are only weakly predictive of acidosis in the newborn. Inadequate oxygenation can cause the blood to become dangerously acidic. Researchers measured oxygenation in 18,250 newborns, and found that umbilical vein oxygen saturation averaged 63%, umbilical artery saturation averaged 24%, and fractional oxygen extraction averaged 62%. Babies with the umbilical cord wrapped around the neck, delivered by cesarean section after labor, or delivered postterm had higher oxygen extraction values, indicating greater fetal compromise.