Background: This study was undertaken to evaluate the effects of maternal central hemodynamics on fetal heart rate patterns near term, with special regard to the maternal body position.
Methods: Brief non-stress test and bioimpedance cardiography were carried out in the supine position, then repeated in a full left lateral decubitus position of mothers with singular, 36-39 week-old normal pregnancies in 106 cases. Computer-aided data were processed by SPSS statistic program.
Results: Due to the appearance of inferior vena cava syndrome, examinations had to be interrupted in 6 cases. Analysis of 100 complete registrations revealed a significantly increased number of accelerations, overall and short-term variations, and longer high episodes with lower basal fetal heart rates were found in the lateral decubitus than in the supine maternal position. Turning to the left resulted in a significant increase of the stroke volume; however, due to decreasing pulse rate, the cardiac output remained unchanged. Parameters of non-stress test showed correlations to hemodynamic indices. In the supine position, the short-term variation correlated with cardiac output (r=0.232, p=0.020); in the left lateral position, the number of accelerations correlated with stroke volume (r=0.221, p=0.027) and cardiac output (r=0.220, p=0.028). Changes of stroke volume due to altered body position correlated to similar changes of overall variation (r=0.264, p=0.018), and marginally to those of short-term variation (r=0.221, p=0.051).
Conclusion: Maternal central hemodynamics influences fetal heart rate patterns in connection with different maternal body position.