Binary Symbolic Dynamics of Fetal Heart Rate Reflects Individual Gestational Development

Fetal heart rate and its variability (HRV) changes with gestational age reflecting fetal growth and the increase of neural integration. The individual gestational development is consistently reflected by the amount of irregularity of fetal HRV. We investigated binary symbolic dynamics of fetal heart rate with respect to individual changes during gestation. In 11 fetuses 215 fetal magnetocardiograms were acquired during the second and third trimester. Short term beat-to-beat changes reflecting acceleration and deceleration of heart rate were coded in 4 bit binary patterns. To reduce redundancies in the patterns five pattern sets were created according to the complexities of the 2⁴ different patterns. The occurrence of two pattern sets consistently decreased individually with progressing gestation (R² = 0.38, CI 0.00-0.71 and R² = 0.24, CI 0.02-0.68). The course over all fetuses was less consistent. Hence, symbolic dynamics analysis reflects individual heart rate development over gestation.