Instability and frequency-domain variability of heart rates in fetuses with or without growth restriction affected by...

This study investigated how the instability and frequency-domain variability in heart rates differ between fetuses affected only by severe preeclampsia and fetuses affected by both severe preeclampsia and growth restriction. From their antepartum fetal heart rates and those of control fetuses, the very short-term intermittency (C1alpha) and the spectral powers were calculated to evaluate the instability and frequency-domain variability, respectively. The fetuses affected only by severe preeclampsia showed abnormally high C1alpha and low- and high-frequency power. The fetuses affected by severe preeclampsia and growth restriction showed even higher C1alpha than that of the fetuses affected by severe preeclampsia and abnormally reduced low-frequency power. Conclusively, when compared to the heart rates of fetuses affected only by severe preeclampsia, the heart rates of fetuses affected by severe preeclampsia and growth restriction showed a greater abnormal instability and an abnormally reduced variability at low-frequency range.