An estimate of fetal autonomic state by time-frequency analysis of fetal heart rate variability

Abstract

In this study we present a noninvasive method that enables the investigation of the fetal heart rate (FHR) fluctuations. The objective was to design a quantitative measurement to assess the fetal autonomic nervous system and to investigate its development as a function of the gestational age. Our Medical Physics group has developed a complex algorithm for online beat-to-beat detection of the fetal ECG (FECG), extracted from the maternal abdominal ECG signal. We used our previously acquired FECG data, which includes noninvasive recordings of 200 maternal abdominal ECG signals. From these, we chose 35 cases of healthy pregnancies that we divided into three groups according to gestational age: Group 1, 23 +/- 2 wk; Group 2, 32 +/- 1 wk; and Group 3, 39 +/- 1 wk. The FHR variability was analyzed by a time-frequency decomposition based on a continuous wavelet transform. We showed that, independent of the gestational age, most of the FHR power is concentrated in the very-low-frequency range (0.02-0.08 Hz) and in the low-frequency range (0.08-0.2 Hz). In addition, there is power in the high-frequency range that correlates with the frequency range of fetal respiratory motion (0.4-1.7 Hz). In the intermediate-frequency range (0.2-0.4 Hz), the power is significantly smaller. The changes in the average power spectrum in relation to gestation time were carefully and quantitatively examined. The results imply that there is a neural organization during the last trimester of the pregnancy, and the sympathovagal balance is reduced with the gestational age.

Assessment of Fetal Autonomic Nervous System Activity by Fetal Magnetocardiography

“…24 Recently, for fetal heart rate variability, different frequency ranges were proposed from one group. 25 However, there is no apparent standard defi nition for the fetal heart rate variability yet. In the present study, FMCG signals were generally too weak to enable a precise analysis of fetal ANS activity to be performed prior to 28 weeks of pregnancy.…”

Novel Possibilities for the Diagnosis of Fetal Distress in Pre-eclamptic Women

“…1,2,5 Mutual activation of vagal and sympathetic branches of autonomic function may provoke fetal aspiration. Fetal intestinal hypermotility and meconium passage based on increased catecholamines level accompanied by respiratory activity could induce intrauterine aspiration.…”

“…Fetal heart rate variability (HRV) is a convenient tool for the fetal biophysical activity and neurodevelopmental investigations. 4,5 But routine HRV parameters obtained with CTG are not absolutely specific for any fetal status within periods of its motile activity and quiet or active sleep. Fetal motile activity is associated with an increased total power (TP) spectrum of HRV and, therefore, with augmented low frequency (LF) and very low frequency (VLF) domain regions values.…”

“…Very low frequency is traditionally associated with thermal regulation, the function of the hypothalamic-pituitary-adrenal axis and renin-angiotensin system activity. 5 The periods of fetal respiratory movements are accompanied with high frequency (HF) domain region predominance. This peculiarity demonstrates the vagal nature of cardiac and respiratory synchronization.…”

“…It may complicate the interpretation and increase the level of unfounded cesarean deliveries. [3][4][5][6] Additional investigation of the fetal ECG morphological parameters could contribute to better diagnostics of its functional status. It has been revealed that increased T/QRS ratio due to elevated T-wave was a marker of the fetal distress.…”