Maturation of fetal cardiac autonomic control as expressed by Fetal Heart Rate variability

The objective of this study was to establish quantitative parameters for estimating the fetal autonomic nervous system (ANS) maturation, derived from the fetal heart rate (FHR) variability. A fetal ECG was non-invasively obtained by extraction from the maternal abdominal ECG signal, which allowed for beat-to-beat detection of the fetal heart beats. 35 healthy pregnancies were examined and divided into three groups according to gestational age. FHR variability was analyzed by a time-frequency decomposition based on a continuous wavelet transform (CWT). The results imply that the fetus undergoes a neural organization during the last trimester of pregnancy and that the sympatho-vagal balance is gradually reduced with the gestational age.