ABSTRACT. Maximal flow velocity waveforms were recorded on one occasion from the umbilical artery (UA) and fetal internal carotid artery (ICA) in 240 normal pregnancies and 44 cases of intrauterine growth retardation between 26 and 39 wk of gestation. In normal pregnancy the mean UA pulsatility index (PI) decreased from 1.14 (SD: 20.13) at 26-27 wk of gestation to 0.78 (SD: k0.15) at 38-39 wk. The corresponding decrease in ICA PI was from 1.63 (SD: 20.19) to 1.31 (SD: f 0.21). Mean values of UA PI for normal pregnancies were linearly related to gestational age; for ICA PI this relation appeared to be quadratic. Normal limits according to age were constructed by estimated means 2 2 SD. In intrauterine growth retardation, the UA PI was increased (>2 SD) in 80% of cases, ICA PI was reduced (>2 SD) in only 45%. The outcome of fetuses with intrauterine growth retardation, as expressed by fetal heart rate abnormality, Apgar score at 1 min, and umbilical cord pH, was significantly related to the UA PI but not to the ICA PI. (Pediatr Res 24: [609][610][611][612]1988) Abbreviations FHR, fetal heart rate ICA, internal carotid artery IUGR, intrauterine growth retardation PI, pulsatility index UA, umbilical artery Recently, a Doppler ultrasound method for recording the blood flow velocity waveform in the fetal internal carotid artery was described (1).Preliminary results suggested that in IUGR due to impaired placental perfusion there was a higher percentage of abnormal PI values in the UA than in the ICA (2). It was also suggested that the reduction in ICA PI reflects redistribution of blood flow in the fetus with the aim of maintaining optimal oxygen supply to the fetal brain (2). The question arises as to if this redistribution of blood flow reflects a further deterioration in fetal oxygen supply in the presence of IUGR.The objective of the present study was 3-fold: I) to establish the normal distribution of UA PI and ICA PI during the third trimester of pregnancy; 2) to determine the degree of abnormality of UA PI and ICA PI during this period of gestation in the presence of IUGR due to impaired placental perfusion; 3) to relate UA PI and ICA PI to fetal well-being as expressed by antenatal fetal heart rate patterns before delivery, Apgar score at 1 min, and umbilical arterial pH. SUBJECTS AND METHODSA combined mechanical sector and pulsed Doppler system (Diasonics CV 400) with a carrier frequency of 3.5 and 3 MHz was used for blood flow velocity measurements in the fetal internal carotid artery and UA. The energy output of the pulsed Doppler transducer was 1.5 mW/cm2 (spatial peak, temporal average). The maximum flow velocity waveform in the internal carotid artery was obtained at the level of the bifurcation into the middle and anterior cerebral artery (1). The sample size of the Doppler probe, necessary for sampling frequency shifts originating from the moving erythrocytes within a vessel, was 4 mm. This allowed clear signals from the internal carotid artery without interference from other nearby vessels such as t...

Summary. The relation between the blood flow velocity waveform in the fetal internal carotid artery (n= 12) and umbilical artery (n= 15) and fetal behavioural states at 37–38 weeks of gestation was studied. In the fetal internal carotid artery, under standardized fetal heart rate conditions, the pulsatility index (PI), as a measure of peripheral vascular resistance, was significantly lower during behavioural state 2F (active sleep) compared with state 1F (quiet sleep) according to the classification by Nijhuis et al. (1982), suggesting increased fetal cerebral blood flow during state 2F. In the umbilical artery, no significant difference in PI between the two behavioural states could be established. This suggests a fetal origin of the state dependency observed in fetal blood flow velocity waveforms.

Summary. Maximal flow velocity waveforms were recorded in the internal carotid artery (ICA), middle cerebral artery (MCA), posterior cerebral artery (PCA) and anterior cerebral artery (ACA) in 55 normal pregnancies and 14 complicated by intrauterine growth retardation between 25 and 41 weeks gestation. In normal pregnancy, acceptable flow velocity waveforms were obtained in the IC A in 89%, in the MCA in 91%, in the PCA in 58% and in the ACA in 64%. A decrease in pulsatility was observed in all four intracranial arteries during the latter weeks of gestation. In growth‐retarded pregnancies, pulsatility in all vessels was significantly reduced compared with normal pregnancy, suggesting participation of all major intracranial arteries in a brain‐sparing effect in the presence of chronic fetal hypoxia.

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