Fetal cerebral oxygenation measured by near-infrared spectroscopy shortly before birth and acid-base status at birth

Abstract

Objective: To test the hypothesis that the mean cerebral oxygen saturation measured by near-infrared spectroscopy shortly before delivery correlates with fetal acid-base status in umbilical cord blood.

Methods: A specially designed optical probe was inserted through the dilated cervix and placed against the fetal head during labor in 41 women. Changes in cerebral oxyhemoglobin and deoxyhemoglobin concentrations were measured continuously, and the mean cerebral oxygen saturation was determined over a 10-minute period within 30 minutes of delivery. Umbilical arterial and venous blood acid-base status was assessed immediately after birth and then correlated to the values for mean cerebral saturation.

Results: Values for mean cerebral oxygen saturation could be determined in 33 fetuses. Umbilical cord artery and vein pH (r = 0.82 and r = 0.79, respectively) showed significant positive correlations (P < .001), whereas base deficit (r = -0.73 and r = -0.71) and carbon dioxide pressure (r = -0.68 and r = -0.63) showed significant negative correlations (P < .001) with mean cerebral oxygen saturation measured within 30 minutes before birth. There was also a significant positive correlation between umbilical vein oxygen pressure and mean cerebral oxygen saturation (r = 0.51, P < .01).

Conclusion: Fetal umbilical blood gas and acid-base status at birth showed significant correlations with mean cerebral oxygen saturation measured shortly before delivery. Low values for saturation were related to both respiratory and metabolic acidemia.