Diurnal rhythms in fetal heart rate baseline and sustained fetal tachycardia in twin pregnancy.

OBJECTIVE: To elucidate the synchronization of phases of diurnal rhythms in fetal heart rate (FHR) baseline between twin fetuses and the occurrence of sustained fetal tachycardia. METHODS: FHR was simultaneously recorded in twins for 24 h in 7 monochorionic diamniotic (MD) and 8 dichorionic diamniotic (DD) twin pregnancies at 35 to 38 weeks of gestation. The diurnal rhythms of the hourly mean FHR baseline were tested in each fetus, and the time of occurrence of sustained fetal tachycardia was compared between twins. The correlation coefficients and phase lags of diurnal rhythms between the hourly mean FHR baselines of twins were calculated in each case. RESULTS: There were significant diurnal rhythms in the hourly mean FHR baselines of all twin fetuses (p<0.01). The patterns of diurnal rhythms were similar for each pair of twins, with the exception of the periods of sustained fetal tachycardia. Sustained fetal tachycardia was not coincident between twins. Analysis in which the periods of sustained fetal tachycardia were excluded demonstrated a significant correlation between the hourly mean FHR baselines of twins in all cases (p<0.01). In the case of DD twins, the phase lag between twins was 0; however, phase lags were observed in 4 cases of MD twins. CONCLUSIONS: The results of this study revealed that the diurnal rhythms in the FHR baseline correlated well between twins, and that the occurrences of sustained fetal tachycardia were completely independent.

Analysis of the influence of diurnal variation in maternal movements on fetal heart rate acceleration.

To determine the influence of diurnal variation in maternal movements (MM) on fetal heart rate (FHR) accelerations, 24-hour maternal heart rates (MHR), MM and FHR recordings were made simultaneously on nine healthy pregnant women at 36-39 weeks of gestation. Correlations between the diurnal variations in maternal factors and FHR parameters; that is, baseline FHR, amplitude, duration and hourly percentage of time spent in accelerations, were examined. Only a few cases showed a significant correlation between acceleration parameters and the diurnal variation of MHR or MM, while most cases indicated a high correlation between the diurnal variation in baseline FHR and that of maternal factors. In conclusion, the occurrence and form of accelerations might be independent of maternal activity.