M.J. Noordam

The blood flow velocity waveform in the fetal internal carotid and umbilical artery; its relation to fetal behavioural states in normal pregnancy at 37–38 weeks

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.

The blood flow velocity waveform in the fetal descending aorta: its relationship to fetal behavioural states in normal pregnancy at 37–38 weeks

In 13 normal pregnancies, the relationship between the blood flow velocity waveform at the lower thoracic level of the fetal descending aorta and fetal behavioural states at 37-38 weeks of gestation was studied. The pulsatility index (PI), as a measure of peripheral vascular resistance, was significantly lower during state 2F compared to state 1F according to the classification by Nijhuis et al. (Nijhuis, J.G. et al. (1982) Early Hum. Dev., 6, 177-195), suggesting an increased perfusion of the fetal skeletal musculature to meet the energy demand needed for the raised muscular activity during state 2F; A significant inverse relationship (P less than 0.001) was established between PI and FHR in state 2F; this was mainly determined by a significant rise in end-diastolic flow velocity (P less than 0.02). Both the behavioural state and FHR should be taken into account when evaluating flow velocity waveforms in the fetal descending aorta during the latter weeks of pregnancy.

Fetal internal carotid and umbilical artery blood flow velocity waveforms as a measure of fetal well-being in intrauterine growth retardation.

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: ±0.13) at 26–27 wk of gestation to 0.78 (SD: ±0.15) at 38–39 wk. The corresponding decrease in ICA PI was from 1.63 (SD: ±0.19) to 1.31 (SD: ±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 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.

Doppler colour flow imaging of fetal intracerebral arteries and umbilical artery in the small for gestational age fetus

Objective To assess with Doppler colour flow imaging whether a brain‐sparing effect is present in all cerebral arteries of the circle of Willis in the small for gestational age fetus, to determine which cerebral flow velocity parameter is most discriminating in this pathological condition, and to relate this parameter to the umbilical artery pulsatility index.

The blood flow velocity waveform in the fetal descending aorta; its relationship to behavioural states in the growth-retarded fetus at 37-38 weeks of gestation

In 12 patients with intrauterine growth retardation (IUGR), the relationship between the blood flow velocity waveform at the lower thoracic level of the fetal descending aorta and fetal behavioural states at 37-38 wk of gestation was studied. A significant inverse relationship (P less than 0.001) was established between pulsatility index (PI) and fetal heart rate (FHR) in state 1F and 2F. The PI as a measure of peripheral vascular resistance, demonstrated a marked increase compared to normal pregnancy. There is a virtual overlap of PI values originating from state 1F and 2F according to the classification by Nijhuis et al. (J.G. Nijhuis, H.F.R. Prechtl, C.B. Martin, Jr. and R.S.G.M. Bots (1982) Early Hum. Dev. 6, 177-195). The peripheral vasoconstriction present in IUGR seems to overrule state dependent PI fluctuations. The marked rise in PI, particularly at lower FHR and the constancy of PI in relation to fetal behavioural states can be considered vascular adaptations, which are instrumental in the centralization of the fetal circulation, with the aim of favouring blood supply to the brain, heart and adrenals during IUGR.

The Doppler Flow Velocity Waveform in the Fetal Internal Carotid Artery with Respect to Fetal Behavioural States

Doppler flow velocity waveforms in the fetal internal carotid artery were recorded in 21 normal pregnancies during fetal behavioural state IF (quiet sleep) and 2F (active sleep) according to Nijhuis and co-workers, from the 36th week of gestation onwards. The present study confirms the earlier finding of a significant reduction of the pulsatility index (PI) in state 2F as compared to state 1F at 37-38 weeks of gestation and demonstrates that this difference in PI exists throughout the entire period, in which fetal behavioural states have been described. Furthermore, it is demonstrated that there is a significant reduction in PI of this vessel during the last 4 weeks of gestation, suggesting a haemodynamic redistribution, favouring blood supply to the brain during the latter weeks of gestation.

The blood flow velocity waveform in the fetal internal carotid and umbilical artery; its relation to fetal behavioural states in the growth retarded fetus at 37–38 weeks gestation

Summary. In eight women whose fetuses showed evidence of intrauterine growth retardation (IUGR), the relation was examined between the blood flow velocity waveform in the fetal internal carotid and umbilical artery and fetal behavioural states at 37–38 weeks gestation. In both vessels there was a virtual overlap of pulsatility index values originating from state IF and 2F, reflecting behavioural state independency. In the internal carotid artery this state independency is associated with moderately reduced pulsatility index values.

The blood flow velocity waveform in the fetal descending aorta; its relationship to fetal heart rate pattern, eye and body movements in normal pregnancy at 27–28 weeks of gestation

In 13 normal pregnancies at 27-28 weeks of gestation the blood flow velocity waveform at the lower thoracic level of the fetal descending aorta was studied in relation to fetal heart rate pattern (FHRP), fetal eye movements (FEM) and fetal body movements (FBM). State parameter combinations in which high fetal heart rate (FHR) variability was present, were associated with a significant reduction in pulsatility index (PI) as compared with periods in which low FHR variability was present, irrespective of FEM and FBM, indicating a reduced peripheral vascular resistance. At 27-28 weeks of gestation FHR variability and PI might be linked to baroreceptor sensitivity. PI values derived from combinations FHRP-A, FEM(-), FBM(-) and FHRP-B, FEM(+), FBM(+) showed a significant inverse relationship (P less than 0.05) with FHR. FHR and FHR variability should be taken into account when studying flow velocity waveforms in the fetal descending aorta at 27-28 weeks of gestation.

Behavioural States and Blood Flow Changes in the Human Fetus

In the human fetus behavioural states were studied from fetal heart rate recordings alone (de Haan 1979; van Geyn et al. 1980), and in conjunction with body movements (Timor-Tritsch et al. 1978; Natale 1985), resulting in the description of quiet and activity phases. The observations did not provide conclusive proof of the presence of true behavioural states in the human fetus since both fetal heart rate and fetal heart rate variability are affected by fetal motility (Wheeler and Guerard 1974). Nijhuis et al. (1982) stated that the presence of behavioural states can only be established following fulfillment of a number of criteria: (a) particular conditions of several variables must recur in specific, fixed combinations; (b) these combinations must be temporally stable; (c) there should be clear transitions between states.