Computerized cardiotocography: correlation between STV > 4 ms and response of fetal cardiac frequency to vibroacoustic stimulation test

Introduction: In classic cardiotocography, a fetus is considered active when there are two transitory accelerations (TA) or elevation of 20 bpm in cardiac frequency after vibroacoustic stimulation test. In computerized cardiotocography there must an instant variability, also named short‐term variation (STV), higher than 4 ms. Objective: Comparison between STV > 4 ms and fetal response to acoustic stimulus. Patients and methods: Twenty‐four normal pregnant were analyzed between 30 and 36 weeks by computerized cardiotocography (SYS 8002). If STV > 4 ms, but TA is absent after 10 min, a vibroacoustic stimulation test was done for 3 s. The fetus was considered reactive when heart rate increased by 20 bpm for 3 min. The fetus was considered hyper‐reactive when heart rate increased less than 20 bpm or duration of response less than 3 min. Results: Among 24 fetuses, 20 (87%) were considered reactive after vibroacoustic stimulation test (elevation of 20 bpm for 3 min or more). Only four fetuses (13%) were hyperactive. Conclusion: When STV > 4 ms fetuses are reactive in 87% cases and hyperactive in 13%. The STV can be used as isolated parameter for assessment of fetal well‐being.