Fetal acoustic stimulation in early labor and pathologic fetal acidemia: A preliminary report

Objective: To determine if a nonreactive response to fetal acoustic stimulation in early labor can predict a significantly higher risk of umbilical arterial pH <7.10 or <7.00. Methods: Fetal acoustic stimulation was applied to the fetuses of term parturients (gestational age ≥37 weeks) with cervical dilation of ≤5 cm. The responses to stimulation were correlated with cesarean delivery for fetal distress and umbilical arterial pH. Student's t-test, Chi-square, and Fisher exact test were used; P < 0.05 was considered significant. Relative risks (RR) and 95% confidence intervals (CI) were calculated. Results: The study population contained 271 subjects, of which 90% (244) had a reactive response following acoustic stimulation and 10% (27) a nonreactive response. The maternal demographics, time interval from stimulation to delivery (8.3 ± 8.7 vs. 8.3 ± 8.4 h; P = 1.00) were similar in the two groups. Compared to those with a reactive response, patients with a nonreactive response had a significantly greater risk for: 1) cesarean delivery for fetal distress (2.0% vs. 11.1%; P = 0.03, RR 4.1, 95% CI 1.5, 60.5), 2) umbilical arterial pH <7.10 (2.0% vs. 14.8%; P = 0.007, RR 5.0, 95% CI 2.2, 11.6), and 3) umbilical arterial _pH <7.00 (0.8% vs. 7%; P = 0.05, RR 5.0, 95% CI 1.8, 15.2). Conclusion: A nonreactive response to fetal acoustic stimulation in early labor is associated with a significantly increased risk for cesarean delivery for fetal distress and neonatal acidosis. This finding extends the potential value of acoustic stimulation as an intrapartum admission screening test.