Vibroacoustic stimulation (VAS), sometimes referred to as fetal vibroacoustic stimulation or fetal acoustic stimulation test (FAST), is the application of a vibratory sound stimulus to the abdomen of a pregnant woman to induce FHR accelerations. The presence of FHR accelerations reliably predicts the absence of fetal metabolic acidemia. Vibroacoustic stimulation is typically used during a nonstress test (NST).
In 2013, the Cochrane Database of Systematic Reviews concluded that there was insufficient evidence from randomized trials to support its use to assess fetal well-being in labor. A related Cochrane Review, however, concluded that its use in antenatal testing did reduce the incidence of non-reactive cardiotocography and the overall testing time.
^East, C. E.; Smyth, R. M.; Leader, L. R.; Henshall, N. E.; Colditz, P. B.; Lau, R.; Tan, K. H. (2013). "Vibroacoustic stimulation for fetal assessment in labour in the presence of a nonreassuring fetal heart rate trace". In East, Christine E. "Cochrane Database of Systematic Reviews". The Cochrane database of systematic reviews1: CD004664. doi:10.1002/14651858.CD004664.pub3. PMID23440793.edit
^Tan, K. H.; Smyth, R. M.; Wei, X. (2013). "Fetal vibroacoustic stimulation for facilitation of tests of fetal wellbeing". In Tan, Kelvin H. "Cochrane Database of Systematic Reviews". The Cochrane database of systematic reviews12: CD002963. doi:10.1002/14651858.CD002963.pub2. PMID24318543.edit