New computerized fetal heart rate analysis for surveillance of intrauterine growth restriction

Objective: Decreased fetal heart rate variability is associated with higher perinatal morbidity and mortality in intrauterine growth restriction (IUGR). This study used a new method [phase-rectified signal averaging (PRSA)] to calculate acceleration- and deceleration-related fluctuations of the fetal heart rate. Method: Cardiotocograms from 74 growth-restricted and 161 normal fetuses were included. Both groups were matched for gestational age. The transformed PRSA signal was quantified by the acceleration-related parameter-averaged acceleration capacity (AAC) and compared to the standard short-term variation (STV). Mann-Whitney test and receiver operator characteristic (ROC) curves were used for statistical analysis. Results: For AAC, the median values of the IUGR group and control group were 1.97 bpm [interquartile range (IQR): 1.66-2.23] and 2.49 bpm (IQR: 2.24-2.72), respectively. For STV, these values were 5.44 ms (IQR: 4.49-7.38) and 7.79 ms (IQR: 6.35-9.66), respectively. The area under the ROC curve was 81.4% for AAC and 70.5% for STV. Conclusion: The results of AAC are in both groups comparable to STV. Longitudinal studies are needed to investigate the association of AAC with the clinical outcome of the newborn.