Monitoring Fetal Heart Rate during Pregnancy: Contributions from Advanced Signal Processing and Wearable Technology
Table 2
Methods, extracted parameters, sequence lengths, and hypotheses for using the relevant parameter.
Method
Parameters
Sequence length
Hypothesis
Frequency domain analysis: periodogram and autoregressive model Measurement of spectral components in defined frequency bands
% of spectral power (msec2) in frequency bands: Low frequency 0.03–0.15 Hz Movement (activity) frequency 0.15–0.5 Hz High frequency 0.5–1 Hz LF/(MF + HF)
3 min 360 values
Quantification of the activity of the autonomic nervous system
Time domain analysis: morphological HR modification and variability
STV (msec) II
1 min 120 values
Variability in the short period
FHR avg (msec) LTI (msec)
3 min 360 values
Variability in the long period
Approximate entropy
ApEn(, ) = 1, 2; = 0.1, 0.15, 0.2
3 min values
Recurrent patterns
Sample entropy
SampEn(, ) = 1, 2; = 0.1, 0.15, 0.2
3 min values
Recurrent patterns Basis for investigating repetitive patterns at different time scales
Lempel Ziv complexity (LZC)
LZC binary or ternary coding LZC (2 or 3, = 0, 0.005, 0, 01, 0.2)
Whole recording
Rate of new patterns arising with signal evolution in time
