Preliminary Evaluation of Fetal Congenital Heart Defects Changes on Fetal-Maternal Heart Rate Coupling Strength

Monitoring fetal heart rate in an important aspect in evaluating fetal well being. Maternal-fetal interaction has shown evolution during fetal maturation. In this work, we studied maternal-fetal heart rate synchronization in early and late gestation fetuses. We also evaluated variations in the synchronization due to congenital heart defect (CHD). Maternal-fetal heart rate synchronization for 22 early gestation (Age < 32 weeks), $late gestation (Age >32 weeks) and 7 CHD fetuses (5 of them with gestational age < 32 weeks). The synchronization ratio between the mother and the fetus was more localized at certain fetus heart rate in the early gestation group while it was spreading over more fetal heart rate for the late group. For example, for maternal primary cycle of 3 beat- to-beat (m=3), the synchronization ratio of 5 fetus beats (n=5) contributed 60±30% of the whole coupling ratios for the early group while it contributed 30°30% for the late group (p< 0.01). On the other hand, the coupling ratio of m:n=3:7 contributed 4±17% of the early group and 13±24% for the late group (p< 0.05). The standard deviation of the phase coherence index $(\lambda_{-\mathrm{S}\mathrm{D}})$ for both the late and the CHD groups were significantly higher than the early group at different values. For example, $\lambda -\mathrm{S}\mathrm{D} was 0.006\pm 0.004$ for the early group while it was 0.009±0.008 for the late group (p< 0.01) and 0.01± 0.002 for the CHD group (p< 0.01) for m=3. The variation between the early and late normal groups might indicate a healthy development of the autonomic nervous system while the higher variation in the CHD group could be a good marker for impairment of the cardiac autonomic activity. Further coupling analysis with more abnormal cases is needed to verify these findings.