The Different Abnormalities of Autonomic Nervous Modulation and Instability of Fetal Heart Rate According to Different Etiologies of Intrauterine Growth Restriction

Background and Objectives:The purpose of this study was to examine whether the different etiologies of intrauterine growth restriction (IUGR) produce different autonomic nervous modulation and instability of the fetal heart rate (FHR) regulation. Subjects and Methods:We investigated the frequency-domain variability and instability in the FHR from 150 uneventful pregnancies (control group), 47 pregnancies with idiopathic IUGR (iIUGR group) and 48 with IUGR associated with severe pre-eclampsia of the mother (PEIUGR group). The FHR was analyzed for the power spectrum and very short-term intermittency (C1α), which are used to quantify the instability in FHR. Results:Compared to the control group, the iIUGR group showed significantly increased lowand high-frequency powers (LFP and HFP, respectively). In contrast, the PEIUGR group showed significantly decreased LFP and LFP/HFP ratio, but significantly increased C1α compared to the control and iIUGR groups. Conclusion:The IUGR of an idiopathic cause produces abnormally increased the autonomic modulation of the FHR. In contrast, the IUGR due to pre-eclampsia abnormally decreased the autonomic modulation in the low-frequency range, but increased the instability of the fetal heart rate regulation. (Korean Circulation J 2005; 35:547-552)