During the past 30 years, physicians have increasingly adopted fetal assessment methods based on either resting fetal heart rate (FHR) tracings, that is, the nonstress test (NST), or FHR responses to stimulation from vibroacoustic simulation (VAS) transducers or induced uterine contractions (contraction stress test [CST] or oxytocin challenge test). These tests are popular owing to the common use of electronic fetal monitoring systems and the extensive educational efforts that have promoted their use in ambulatory settings. A substantial published clinical database regarding the utility of these schemes has been assembled from numerous clinical reports and enables prudent clinical application in the contemporary medical environment.<sup>16 Devoe L.D., Castillo R.A., Sherline D.M. The nonstress test as a diagnostic test: A critical reappraisal Am J Obstet Gynecol 1985 ;  152 : 1047

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Fetal heart rate testing has considerable benefits and notable shortcomings that must be appreciated to provide optimal perinatal care. This article summarizes the physiologic basis for testing, test methodology, test indication and interpretation, and test application. It concludes with an objective assessment of test efficacy and a speculative view of future developments.