title: Increase in regularity of fetal heart rate variability with age.
abstract: It is generally assumed that fetal heart rate variability increases with gestation, reflecting prenatal development of the autonomic nervous system. We examined standard measures quantifying fetal heart rate variability, as well as a complexity measure, approximate entropy, in 66 fetal magnetocardiograms recorded from 22 healthy pregnant women between the 16th and 42nd week of gestation. In particular, regularity in the fetal RR interval time series was assessed on the basis of symbolic dynamics. The results showed that, beside an overall increase in fetal heart rate variability and complexity during pregnancy, there was also an increase in specific sets of binary patterns with low approximate entropy, i.e., a high degree of regularity. These sets were characterized by short epochs of heart rate acceleration and deceleration, and comparison with surrogate data confirmed that their random occurrence is rare. The results most likely reflect the influence of increasingly differentiated fetal behavioral states and transitions between them in association with fetal development.
authors.affiliation: Department of Biomagnetism, Grönemeyer Institute for Microtherapy, University Witten/Herdecke, Bochum, Germany. petervl@microtherapy.de
authors.forename: Peter
authors.initials: P
authors.lastname: Van Leeuwen
authors.forename: Dirk
authors.initials: D
authors.lastname: Cysarz
authors.forename: Silke
authors.initials: S
authors.lastname: Lange
authors.forename: Dietrich
authors.initials: D
authors.lastname: Grönemeyer
mesh_terms: D000375:Aging / Q000502:physiology*; D000465:Algorithms; D001683:Biological Clocks / Q000502:physiology*; D003198:Computer Simulation; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D008955:Models, Cardiovascular