Mobile Phone Application Versus Handheld Device for Fetal Vibroacoustic Stimulation

This is a randomized controlled single blinded crossover study to compare fetal vibroacoustic stimulation with a handheld device to a mobile phone application designed for this study. The handheld device, the Corometrics model 146, was previously marketed and sold for fetal stimulation and is modeled after devices used as artificial larynxes. The mobile phone application uses an iPhone\'s built in vibration with acoustic stimulation from the speaker at 2,000 Hz frequency at a sound level of 74 decibels when measured at 1 meter distance. The investigators\' hypothesis is that the mobile phone application will elicit a fetal response (defined as one or more fetal heart rate accelerations in 15 minutes) at a similar rate to that of the handheld device. Fetal vibroacoustic stimulation is commonly used during antenatal tests of fetal well being such as a non-stress test. Fetal vibroacoustic stimulation works by arousing the fetus to a state of wakefulness during which reassuring fetal movements and associated fetal heart rate accelerations occur. During a non-stress test, two or more fetal heart rate accelerations in 20 minutes constitutes a reassuring test. Fetal vibroacoustic stimulation has been shown to decrease the false positive rate of non-stress testing without increasing the false negative rate. This study will compare the frequency that one or more fetal heart rate accelerations occur in the 15 minutes after vibroacoustic stimulation with the Corometrics-146 fetal acoustic stimulator compared to after vibroacoustic stimulation with a mobile phone application designed for the study.