Comparison of fetal heart rate variability by symbolic dynamics at the third trimester of pregnancy and low-risk parturition

Cristian Iván Montalvo-Jaramillo; Adriana Cristina Pliego-Carrillo; Miguel Ángel Peña-Castillo; Juan Carlos Echeverría; Enrique Becerril-Villanueva; Lenin Pavón; Rodrigo Ayala-Yáñez; Ramón González-Camarena; Karsten Berg; Niels Wessel; Gustavo Pacheco-López; José Javier Reyes-Lagos

doi:10.1016/j.heliyon.2020.e03485

Comparison of fetal heart rate variability by symbolic dynamics at the third trimester of pregnancy and low-risk parturition

Heliyon. 2020 Mar 12;6(3):e03485. doi: 10.1016/j.heliyon.2020.e03485. eCollection 2020 Mar.

Affiliations

¹ Autonomous University of the State of Mexico (UAEMex), Faculty of Medicine, Toluca, 50180, Mexico.
² Metropolitan Autonomous University (UAM), Campus Iztapalapa, Basic Sciences and Engineering Division, Mexico City, 09340, Mexico.
³ Laboratory of Psychoimmunology, National Institute of Psychiatry, "Ramón de la Fuente", Mexico City, 14370, Mexico.
⁴ Maternal and Childhood Research Center (CIMIGen), Mexico City, 09890, Mexico.
⁵ Metropolitan Autonomous University (UAM), Campus Iztapalapa, Biological and Health Sciences Division, Mexico City, 09340, Mexico.
⁶ Cardiovascular Physics, Department of Physics, Humboldt-Universität zu Berlin, Berlin, 10115, Germany.
⁷ Metropolitan Autonomous University (UAM), Campus Lerma, Biological and Health Sciences Division, Lerma, 52005, Mexico.
⁸ Swiss Federal Institute of Technology (ETH) Zurich, Department of Health Sciences and Technology, Zurich, 8092, Switzerland.

Abstract

Fetal heart rate variability (fHRV) is an essential source of information to monitor fetal well-being during pregnancy. This study aimed to apply a nonlinear approach, known as symbolic dynamics (SD), for comparing human fHRV in the third trimester of pregnancy during active fetal state (TT) and active labor at term (P). We performed a longitudinal, prospective, descriptive, and comparative study composed of 42 longitudinal recordings of 5-minutes of fetal heartbeat interval series. Recordings were collected from 21 low-risk, healthy, pregnant women attending the Maternal and Child Research Center (CIMIGen), Mexico City. We calculated relevant linear parameters of fHRV between TT and P stages, such as the percentage of differences between adjacent RR intervals >5 ms (PRR5, related to vagal modulations) and other SD parameters such as the percentage of no variations between three successive symbols (%0V, reflects sympathetic modulations) and the probability of low variability with a threshold of 4 ms (POLVAR4, associated with a low variability). We identified statistical differences for PRR5 between TT and P (37.13% [28.47-47.60%] vs. 28.84% [19.36-36.76%], p = 0.03), respectively. Also, for 0V% (65.66% [59.01-71.80%] vs. 71.14% [65.94-75.87%], p = 0.03) and for POLVAR4 values (0.06 [0.04-0.11] vs. 0.15 [0.09-0.24], p = 0.002), respectively. Our results indicate that during parturition, the short-term fetal fHRV is decreased, showing a decreased vagal modulations and higher adrenergic response of the heart. These autonomic modifications may result from the fetal response to the stressful inflammatory challenge of labor. We thus confirmed that the analysis of the SD applied to fHRV time series could be a potential clinical biomarker to differentiate the fetal autonomic cardiac condition at different stages of pregnancy.

Keywords: Biomedical engineering; Fetal heart rate variability; Labor; Medical physics; Nervous system; Nonlinear signal processing; Obstetrics; Symbolic dynamics; Term birth.