Fetal Heart-Rate Variability: Validation of a New Continuous, Noninvasive Computerized Analysis.

OBJECTIVE: We developed a computerized heart-rate variability index related to the fetal parasympathetic activity: the Fetal Stress Index (FSI). The objective was to determine whether the FSI is related to the visual analysis of the fetal heart rate (FHR). METHODS: Thirty tracings recorded at a labor ward were classified according to the NICHD categories: (I) normal FHR tracing, (II) intermediate risk of acidosis, and (III) high risk. FSI was calculated as minimum, maximum, and mean, and was evaluated before the onset of the FHR pattern, during the 10 min following, and between 10 and 20 min after that. RESULTS: The FSI for categories II and III was similar to that of category I before the onset of the FHR pattern. FSI min was lower just after the onset of the abnormal FHR in category III, compared with that of category I (33 vs. 43, p < 0.001). Between 10 and 20 min after the onset of the abnormal FHR, we observed a significant reduction in FSI min in categories II and III (44 vs. 39 vs. 29.7, p < 0.0001). CONCLUSION: Although further studies are necessary for the sake of clinical validation, FSI could constitute an interesting method for the evaluation of fetal well-being.