Longitudinal Assessment of Fetal Heart Rate Variability During Pregnancy

Inadequate development of the fetal autonomic nervous system (ANS) during gestation can lead to health problems not only in the perinatal period but well into adulthood. Assessing fetal heart rate variability (fHRV) may allow for tracking fetal autonomic development and identification of abnormalities. A HRV methodology which is well-suited to this purpose is phase rectified signal averaging (PRSA). While PRSA has been used in assessing autonomic dysfunction related to complications such as fetal growth restriction, knowledge on how PRSA features change with gestational age is limited. In this paper, we use PRSA to analyze a dataset comprising of repeated abdominal ECG measurements acquired throughout healthy pregnancy (29 participants, 184 recordings) to capture how PRSA features evolve over the second half of gestation. Results show that all features change significantly (p < 0.01), typically increasing from 22 to around 31 weeks (likely due to quicker signaling between nerve cells, corresponding to the rapidly maturing parasympathetic nervous system) and then stabilizing or slightly decreasing thereafter owing to better control of the heart rate by the mature fetal ANS. We conclude that PRSA features change with progressing gestation and may be a useful tool for tracking the maturation of the fetal ANS.