Alterations in Maternal–Fetal Heart Rate Coupling Strength and Directions in Abnormal Fetuses

Figures

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  Figure 1. A Sample of fetal and maternal ECGs.

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  Figure 2. Processed fetal and maternal heart rates (fBBI and mBBI).

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  Figure 3. NSTPDC indices (NF: Normalization factor) (A), A_fBBI 1: N indicates the causal coupling strength originating from fBBI (fetus) toward mBBI (mother) (B) A_mBBI→fBBI indicates the causal coupling strength originating from mBBI (mother) toward fBBI (fetus) (C) vs. gestational age. The numbers indicate the ID of the abnormal cases. The coupling from fetus to mother for the normal group (B) showed a significant correlation with age (r = −0.3, p = 0.013). Solid line represents linear fit for the normal group and dashed lines indicate 95% confidence interval.

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  Figure 4. 2D NSTPDC plots for: (A) fetal auto-coupling (fBBI→fBBI), (B) maternal-fetal coupling (mBBI→fBBI), (C) fetal-maternal coupling (fBBI→mBBI), and (D) maternal auto-coupling (mBBI→mBBI) for a normal fetus with age: 30 weeks. The window length is 160 samples.

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  Figure 5. 2D NSTPDC plots for: (A) fetal auto-coupling (fBBI→fBBI), (B) maternal-fetal coupling (mBBI→fBBI), (C) fetal-maternal coupling (fBBI→mBBI), and (D) maternal auto-coupling (mBBI→mBBI) for a fetus with tachycardia (ID: 13 from Table 2). The window length is 160 samples.

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  Figure 6. 2D NSTPDC plots for: (A) fetal auto-coupling (fBBI→fBBI), (B) maternal-fetal coupling (mBBI→fBBI), (C) fetal-maternal coupling (fBBI→mBBI), and (D) maternal auto-coupling (mBBI→mBBI) for a fetus with SSS (ID: 7, Table 2). The window length is 160 samples.

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  Figure 7. Correlation between coupling parameters (A_fBB →mBB and A_mBB →fBB) and RMSSD (A,B) and Renyi entropy (C,D) for normal and abnormal groups (solid line represents linear fit for normal, dashed line represents linear fit for abnormal group).