[Studies on fetal middle cerebral artery blood flow velocity waveforms in the intrapartum period].

The effects of uterine contractions on fetal intracranial circulation were studied by means of two dimensional color doppler flow equipment. The Resistance Index of the Middle Cerebral Artery (MCA-RI) was evaluated and the following results were obtained. 1) The MCA-RI value during uterine contraction was significantly higher than that obtained between contractions and the highest MCA-RI value was noted during the active phase, which may mean that the descending fetal head was subjected to the strongest compression at this time. 2) A significant positive correlation was found between intrauterine pressure and the MCA-RI value at any time during labor the course of labor. 3) A significant negative correlation was noted between MCA-RI and FHR. FHR early deceleration (ED) appeared in 67% of the cases with absent end-diastolic flow velocity (AEFV), and in 100% of cases with reverse EFV. It was thus shown that intracranial hemodynamics changed dramatically in the intrapartum period even in the normal fetus.