Fetal acoustic stimulation for rapid intrapartum assessment of fetal well-being.

Fetal heart rate reactions to the fetal acoustic stimulation test (FAST) were prospectively studied in 140 women in early labor. Overall 45 of 140 patients (32%) had one or more complications of pregnancy. All were in the latent phase of labor with a singleton, vertex-presenting fetus. Gestational age ranged from 37-43 wks. The women were screened with a 15-20 min fetal heart rate recording (FHR admission test) before the acoustic stimulation was applied. Results of the FHR admission test and the FAST in women were compared with fetal outcome; which was considered poor when there was perinatal death, a 5 min Apgar score less than 7, fetal distress requiring cesarean section, thick meconium stained amniotic fluid or admission to the neonatal intensive care unit. FAST had better sensitivity (71.4% vs 42.8%), specificity (99.2% vs 97.7%), positive predictive value (83.3% vs 50.0%) and negative predictive value (98.5% vs 97.0%) for poor fetal outcome than the FHR admission test. Fetal acoustic stimulation test in the early intrapartum period may be used as a noninvasive screening method for rapid intrapartum assessment of fetal wellbeing. It may discriminate the compromised from the noncompromised fetus. This clinical application can be helpful in a busy labor room when rapid assessment of fetal health is required.