Reduced maternal–fetal cardiac coupling in moderate preterm labor: a high-resolution symbolic dynamics analysis

Abstract This research explores maternal–fetal heart rhythm coupling (MFHRC) in full-term and moderate preterm labor using high-resolution joint symbolic dynamics (HRJSD) to identify distinct heart rate patterns indicative of physiological system couplings during active labor stages. This study evidences that preterm labor exhibits unique MFHRC patterns compared to full-term labor, potentially reflecting physiological responses and system complexities differences. The analysis involved 25 maternal–fetal RR time series from women in active full-term labor and 18 from those in moderate preterm labor. HRJSD was utilized to dissect the degree of coupling by examining specific maternal–fetal heart rhythm patterns and calculating global Shannon entropy for both groups. We observed that specific dominant heart rate patterns are preserved in both term and moderate preterm labor, suggesting an intrinsic aspect of cardiovascular coupling irrespective of the labor's condition. Additionally, we found variations in non-dominant patterns between term and preterm labor, which may reflect subtle differences in cardiac responses, hinting at possible adaptive fetal strategies in response to preterm labor conditions. An important finding of our research is the overall decrease in MFHRC in preterm labor, as indicated by higher Shannon entropy values. This decrease suggests a reduced synchronization of maternal–fetal heart rate rhythm during labor in preterm conditions. These insights highlight the importance of MFHRC analysis in understanding the distinct physiological interactions between mother and fetus during labor. The study's findings may pave the way for further research on prenatal health and developing interventions that may guide outcomes in preterm labor.