The relationship between heart rate and eye movement in the human fetus at 38-40 weeks of gestation.

The purpose of this study was to compare two different methods for assessing fetal heart rate (FHR)--fetal eye movement (FEM) synchronization: (1) periods of high (HV) and low (LV) variability in the FHR and the presence (EM) and absence (NEM) of FEM were determined by visual inspection and the degree of association between FHR and FEM was assessed in terms of the fraction of study time for which no periods of LV-NEM and HV-EM could be identified; and (2) the maximum cross-correlation coefficient (rmax) and the lag at rmax (Lmax) were determined by direct computer analysis of FHR and FEM data for each fetus. Twenty normal human fetuses between 38 and 40 weeks of gestation were examined for a total of 2051 min (mean 103 min, range 72-150 min). In general, the state HV-EM was observed approximately twice as often as was the state LV-NEM; neither of these two states could be identified during 12.4% of the study time. The coefficient rmax was calculated assuming a sliding 3-min moving window, using either the average FHR (mean 0.53, range 0.31-0.85) or the variability in the FHR (mean 0.52, range 0.18-0.77). No relationship was found between rmax and Lmax calculated using the mean FHR and the fraction of time for which no state could be identified (P = 0.995). When the cross-correlation analysis was performed using FHR variability, a statistically significant relationship was found between the periods of no coincidence (of states LV-NEM and HV-EM) and rmax and Lmax (r2 = 0.32; P = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)