Prospective comparison of the startle test (recoil) and non-stress test.

Objective : Our purpose was to compare fetal heart rate reaction to external physical stimulation with the non-stress test (NST). Methods : This was a prospective study evaluating documentation of fetal heart accelerations by two methods. The standard NST was performed prior to the ultrasound evaluation. The NST results were not available to the ultrasonographer. M-mode ultrasound was used to establish a stable fetal heart rate. The ultrasound transducer was used to stimulate fetal movement by indentations of the uterus over the fetal small parts. A second fetal heart rate was determined within 15 s after stimulation. Results : A total of 122 patients had 159 studies performed. The fetal heart rate range due to fetal startle (recoil) was m 22 to 14 (median of 3) in the 45 fetuses with non-reactive NSTs and 1 to 38 (median of 15) in the 114 fetuses with a reactive NST ( p < 0.001). A receiver operating curve comparing the fetal response to the startle and the NST revealed an area under the curve of 0.9...