The effect of behavioral states on fetal heart rate and middle cerebral artery flow-velocity waveforms in normal full-term fetuses

Objectives: To evaluate the effect of fetal behavioral states on the relationship between fetal heart rate (FHR) and middle cerebral artery resistance index (MCA RI) in normal fetuses. Methods: The FHR and MCA RI of 10 normal cases from 37 to 40 weeks of gestation were recorded consecutively over a 45-min period. Correlations between the MCA RI and FHR during resting and active phases, classified by an actocardiotocogram, were analyzed by simple regression analysis. Results: The mean FHR and MCA RI were significantly higher during the active phase (140.3 +/- 6.6 bpm, 0.79 +/- 0.06) than those during the resting phase (137.4 +/- 6.8 bpm, 0.75 +/- 0.07, P < 0.01, two sample t-test). There was a significant negative correlation (r = -0.22, n = 2642, P < 0.01) between RI and FHR during the active phase and a significant positive correlation (r = 0.28, n = 2066, P < 0.001) during the resting phase. Conclusions: The relationship between FHR and the MCA RI during the resting phase is different from during the active phase. (C) 1997 International Federation of Gynecology and Obstetrics.