DOPPLER VELOCIMETRY OF DIFFERENT SECTIONS OF THE FETAL MIDDLE CEREBRAL-ARTERY IN RELATION TO PERINATAL OUTCOME

To assess the standard curves of pulsatility index (PI) in different s egments of middle cerebral artery (MCA): initial segment (M1) and subc ortical segment (M2); to determine the variation of the flow velocity waveforms (FVW) of the M1 and M2 segments of MCA in presence of fetal distress and to establish the possible correlation between the two seg ments of MCA. 50 normal pregnancies from 25 weeks of gestation to term and 20 pregnancy with alteration of fetal growth rate were investigat ed with serial records of the FVW of the M1 and M2 segments of the MCA and of the umbilical artery (UA) with a colour Doppler system. Severe fetal distress was associated to cerebral-placental ratio below 1 (C/ P < 1). The perinatal outcome was established on the basis: 1) abnorma l intrapartum CTG, 2) emergency cesarean section, 3) Apgar score at 1s t and 5th minute after birth and 4) birth weight centiles. In normal p regnancy PI of M2 was always higher than that of M1: therefore M2/M2 r esulted below 1, with a maximum peak near 32 weeks of gestation. In pr esence of moderate fetal distress only PI of M2 was reduced (M1/M2 > 1 ). It exists a significant difference of PI in M1 and M2 segments of f etal MCA during gestation: thus MCA so it is important to identify the tract of fetal MCA when recording its FVW. Moreover we suppose that a n initial ''cerebral sparing'' effect exists in order to protect the c ortex by the initial hypoxic injury: this is shown by a M1/M2 > 1. The progression of fetal distress results in a greater haemodynamic modif ication, the so called ''brain sparing'' which is usually present when C/P < 1.