Relationship between changes in fetal oxygen saturation during second stage of labor and neonatal outcome in cases of abnormal fetal heart rate

Summary

Arterial oxygen saturation of the fetus during second stage of labor, measured with a fetal pulse oximeter (SpO₂), was compared to neonatal condition assessed by umbilical vein pH and Apgar score. An index was designed in order to quantify the changes in SpO₂ during the second stage of labor. This index was also compared to neonatal outcome.

Fifty-five patients with abnormal fetal heart rate pattern during labor had a continuous monitoring of fetal oxygen saturation using the Nellcor N-400 pulse oximeter and the Nellcor FS-10 sensor. Sixteen patients had a cesarean delivery and were excluded from analysis.

SpO₂ measurement during the last 10 min of labor was significantly correlated to umbilical vein pH and to 1 min Apgar score (p = 0.022 and p = 0.025, respectively). A much higher correlation was found between the index of desaturation and neonatal umbilical vein pH and with 1 min Apgar score (p = 0.002 and P < 0.001, respectively).

If these results are confirmed in a larger series of patients, analysis of the changes in fetal arterial oxygen saturation during labor (index of desaturation) could be a good indicator of the condition of the newborn.