662: Power spectral analysis of trans-abdominal fetal ECG at the beginning of labour as a predictor of adverse pregnancy outcome

Abstract

To evaluate fetal heart rate, obtained by trans-abdominal ECG-RR intervals, by power spectral density (PSD) and compare normal values with findings obtained in acidemic fetuses Non invasive transabdominal fetal ECG with Monica AN24 device was performed in labour in uncomplicated term pregnancies. Thirty-six fetal ECG traces were collected at the beginning of labour from patients that delivered neonates with normal outcome (pH>7.20, BE<5, Apgar at 1 and 5min 10-10). Comparative analysis was performed with two cases with adverse outcome (pH<7.0, BE>12, Apgar at 5 min ≤7). Thirty minutes records were used for each patient. Due to non-uniformly sampled data a Lomb-Scargle periodogram was used to estimate the power spectral density at ultra low (0.00083 – 0.003), very low (0.003 – 0.04), low (0.04 – 0.15 Hz), high (0.15 – 0.4 Hz) and very high frequencies (0.4 – 0.92 Hz). The graph shows the data represented through box plots. The boxes represent the inter-quartile range and the whiskers represent the most extreme data points, which are not considered outliers. The two fetuses with an abnormal hypoxic outcome did not show any difference in power spectral analysis values since their findings fitted within the interquartile range of normal cases. This is the first reported PSD analysis in non-uniformly sampled data by means of Lomb-Scargle periodogram. We were able to define the relative power spectral analysis of ultra low, very low, low, high and very high frequencies of trans-abdominal fetal ECG in early labour in healthy fetuses. Two fetuses that subsequently developed acidemia did not show any difference in power spectral densities in early stages of labour. This finding suggests that possible changes of the autonomous nervous system balance may not present early in labour in cases where intrapartum asphyxia, confirmed at birth, develops progressively during the labour.