Utilization of Fetal Heart Rate Acceleration Following Vibroacoustic Stimulation in Labor to Predict Fetal Acidemia and Base Deficit Levels

Abstract

The absence of a fetal response to vibroacoustic stimulation (VAS) performed during labor may be an indicator of fetal acidemia. A lack of fetal heart rate (FHR) acceleration following VAS has been correlated with fetal scalp blood pH < 7.20. A measurement of pH alone cannot distinguish respiratory from metabolic acidosis. This study correlates the FHR response to VAS during labor with fetal scalp blood pH and base deficit levels. The mean pH and base deficit levels of patients not demonstrating FHR response were 7.24 and 5.90 mEq/L, respectively. A lack of FHR response after VAS was moderately sensitive to detect pH < 7.20 but more sensitive to detect pH < 7.10. A lack of FHR acceleration was moderately sensitive to detect base deficit > 7 mEq/L but was more sensitive to detect levels >10 mEq/L. All patients with pH < 7.20 and demonstrating FHR response after VAS had base deficit < 10 mEq/L. Forty-four percent of patients with pH < 7.20 and no FHR response after VAS had base deficit > 10 mEq/L. This study suggests that VAS during labor can predict fetal acidemia and differentiate between respiratory and metabolic acidosis.

Key Words:

• Vibroacoustic stimulation
• Labor
• Fetal acidemia