Cross-over trial of fetal heart rate response to halogen light and vibroacoustic stimulation

The purpose of this study was to compare the effect of halogen light and vibroacoustic stimulation on fetal heart rate (FHR) responsiveness and on nonstress test (NST) results.

Sixty consecutively-chosen patients between 33 and 39 weeks of gestation underwent an NST on at least three weekly occasions. Each received halogen light (Vector Compact Sport Spot, Ft Lauderdale, FL, USA), vibroacoustic (SolaTone Artificial Larynx, Temecula, CA, USA), and no stimulation in a randomized order. The transabdominal light or vibroacoustic stimulation lasted for 10 seconds. If no initial FHR acceleration occurred, then the stimulus was repeated 10 minutes later up to a maximum of three times. The investigators who interpreted the FHR patterns were blinded as to the type of stimulus used.

Reactive results were present in 171 tests (vibroacoustic: 98.3%; light: 96.6%; none: 93.3%). Compared with no stimulation, the mean difference in time from the onset of recorded "stimulation" to the first FHR acceleration was shorter (p < 0.01) with either light (2.7 minutes, 95% confidence interval (CI) 0.9-4.5 minutes) or vibroacoustic stimulation (2.6 minutes, 95% CI 0.8-4.4 minutes). The mean time difference until a reactive result was also shorter (p < 0.05) with either light (2.7 minutes, 95% CI 0.1-4.9 minutes) or vibroacoustic stimulation (2.4 minutes, 95% CI 0.1-4.7 minutes) than with no stimulation. The need for repeated stimulation during each test was infrequent (light: 5.0%; vibroacoustic: 3.3%). No adverse effect from external stimulation was noted on the FHR tracing.

Halogen light stimulation is an acceptable alternative to vibroacoustic stimulation in provoking a more rapid fetal heart rate response and in shortening the time before a reactive nonstress test result.