DEVELOPMENTAL CHANGES OF LINEAR AND NONLINEAR FETAL HEART RATE DYNAMICS

초록

Objectives: We studied the developmental changes of linear and nonlinear fetal heart rate dynamics. Study Methods: In 580 normal singleton pregnancies(20 weeks or more), we analyzed fetal heart rate of 40 minutes' duration. Linear (Low-[LFP], high-frequency power[HFP] and their ratio) and nonlinear (short-and long-term fractal scaling exponent and approximate entropy[ApEn-T]) analysis were calculated. We also calculate approximate entropy from 1000 point of fetal heart rate during period excluding fetal movement(ApEn-R). Results: LFP and LFP/HFP ratio increased significantly with gestational age(p=0.0001), but HFP did not(p>0.05). The short-term fractal scaling exponent gradually increased with gestational age (p<0.0001). However, long-term fractal scaling exponent did not (p=0.451). ApEn-T steadily decreased after the 29-30 weeks of gestation until term gestation(p<0.05). The ApEn-R showed a tendency to increase with gestational age (p=0.0001). Conclusions: The developmental change of fetal heart rates dynamics differs according to the presence or absence of fetal movement. During total period including fetal movement, the results showed an increase in amplitude of low-frequency periodic oscillation, in short-term temporal correlation with gestational age and decreasing complexity after 29-30 weeks. These findings may be related to the maturation of acceleration pattern with fetal movement, in accordance with autonomic nervous development near term gestation. During the period without fetal movement, the change is characterized by increasing complexity, which means increased variability with advancement of gestational age.