RESUMEN
The value of antepartum fetal heart rate testing has been debated in the last few years. According to several research works, the fetal sleeping periods lead to falsely nonreactive tests. These increase the risk and costs of obstetric care. A randomized prospective clinical trial was undertaken in high risk pregnancies to compare the standard nonstress test with the fetal vibroacoustic stimulation. Acoustic stimulation during 5 seconds with a 75 Hz frequency and 74 dB intensity device was applied to the patients in the study group. Nonreactive results were obtained in 11% of the control group and 3.4% in the study group (z = 2.07, p = 0.00116). A reduction of 5 minutes in the length of the test was observed in the study group. Fetal acoustic stimulation should be considered an alternative to improve the efficacy of nonstress testing, by reducing falsely nonreactive tests results and the time it takes to perform them.