Umbilical Venous Flow Research Articles

Simultaneous measurements of umbilical venous, fetal hepatic, and ductus venosus blood flow in growth-restricted human fetuses

Objective The purpose of this study was to evaluate the changes in the distribution of the umbilical venous blood flow to the liver and to the ductus venosus in intrauterine growth-restricted human fetuses in relationship with dilation of the ductal isthmic diameter. Study design Umbilical venous flow, ductus venosus blood flow, and blood flow to the fetal liver were measured in 56 severely intrauterine growth-restricted fetuses with an abnormal pulsatility index of the umbilical artery and were compared with 137 normal control fetuses. Percentages of umbilical venous blood flow through the ductus venosus and to the fetal hepatic lobes were calculated. Z-scores for control fetuses and intrauterine growth-restricted fetuses were constructed by the evaluation of the inverted smoothed percentiles. The distributions of the Z-scores was compared with a 1-sample t-test. Results The ductus venosus blood flow that was corrected for fetal weight was increased significantly in intrauterine growth-restricted fetuses compared with control fetuses ( P = 0); the median values (interquartile range) for comparable ages of gestation was 41.3 mL/min/kg (range, 26.2-64.0 mL/min/kg) and 30.8 mL/min/kg (range, 19.9-42.8 mL/min/kg), respectively. As a consequence, ductus venosus shunting was increased in intrauterine growth-restricted fetuses compared with control fetuses ( P = 0). In 23 of 30 intrauterine growth-restricted fetuses, the percentage of umbilical blood flow that was shunted through the ductus was>90th percentile of control fetuses. Ductal diameters were significantly greater in growth-restricted fetuses than in control fetuses ( P = .0001). The percentage of blood flow to the right lobe showed a significant reduction ( P = .0223), with evidence of reversed blood flow from the right lobe and portal system into the ductus venosus that was provided both by volume blood flow calculations and by direct pulsed Doppler waveform direction. Conclusion In severe intrauterine growth-restricted fetuses, Doppler examination of blood flow volume proved a significant increase in the shunting of umbilical vein blood flow through the ductus venosus that was associated with the dilation of the ductal isthmic diameter. These changes provide a relatively constant blood flow to the heart and brain at the expense of fetal hepatic perfusion.

Umbilical venous volume flow and fetal behavioral states in the normally developing fetus

To determine the relationship between umbilical venous (UV) volume flow and fetal behavioral states 1F (quiet sleep) and 2F (active sleep) in normal pregnancies at 36-40 weeks of gestation. Fetal behavioral states were established in 17 normal pregnancies by means of combined assessment of fetal heart rate patterns (FHRP), and fetal eye and body movements. UV vessel area (mm(2)) as obtained by tracing the inner vessel area using Labview and Imaq Vision software and UV time-averaged flow velocity (mm/s Doppler) were multiplied to calculate UV volume flow (mL/min) including flow/kg fetus. The pulsatility index (PI) in the umbilical artery was also determined. In each woman, all parameters were measured between three and five times in each behavioral state. Data are reported as mean +/- 1 SD and analyzed by paired t-test. No statistically significant behavioral-state-related changes were observed for UV time-averaged velocity and UV volume flow, resulting in UV volume flow/kg fetus of 69.1 +/- 14.9 mL/min*kg at 1F and 71.6 +/- 12.1 mL/min*kg at 2F (not significant). A statistically significant increase (P = 0.02) was established for UV cross-sectional area (46.4 +/- 8.6 mm(2) vs. 49.0 +/- 10.1 mm(2)) and for fetal heart rate (FHR) from 134.2 +/- 10.3 bpm in 1F to 144.2 +/- 7 bpm in 2F. Umbilical artery PI was not significantly different between the two behavioral states. On the basis of high venous vessel wall compliance, the significant increase in UV cross-sectional area during fetal behavioral state 2F may be determined by a rise in mean venous pressure. The significant rise in FHR may reflect increased fetal cardiac output during state 2F while the resistance at the hepato-ductal pathway remains relatively constant with the purpose of meeting raised energy demands during the active sleep state. This is further supported by the observed trend towards an increase in UV volume flow.

Assessment of fetal liver volume and umbilical venous volume flow in pregnancies complicated by insulin‐dependent diabetes mellitus

To determine fetal liver volume and its relation with umbilical venous volume flow and maternal glycosylated haemoglobin (HbA1c) in pregnancies complicated by diabetes mellitus type I. A cross sectional matched control study. Obstetric out patient clinic, Erasmus MC-University Medical Centre, Rotterdam. Data from fetuses of diabetic women (n = 32; 18-36 weeks) were compared with data from normal controls (n = 32) matched for gestational age. Umbilical venous cross sectional area (mm(2)) and time-averaged velocity (mm/s Doppler) were determined for calculation of volume flow (mL/min) and flow per kilogram fetal weight (mL/min/kg). Umbilical artery pulsatility index was determined. Fetal liver volume measurements were obtained using a Voluson 530-D. Fetal liver volume, umbilical venous volume flow and downstream impedance. A statistically significant difference between fetuses of diabetic women and normal controls was found for liver volume (mean [SD]: 45.9 [34.0] vs 38.3 [28.7] mL), abdominal circumference (22.2 [6.6] vs 21.3 [5.6] cm), estimated fetal weight (1162 [898] vs 1049 [765] g) and fetoplacental weight ratio (0.22 vs 0.19) and liver volume/estimated fetal weight ratio (4.13% [0.007] vs 3.62% [0.009]). Umbilical venous volume flow (mL/min) and umbilical artery pulsatility index were not essentially different between the two study groups, but umbilical venous volume flow per kilogram fetal weight was lower (P < 0.05) in the diabetes group (94.3 [26.1] mL/min kg) compared with normal controls (109.5 [28.0] mL/min/kg). A positive correlation existed between fetal liver volume and maternal HbA1c (P = 0.002). Measurement of fetal liver volume by three-dimensional ultrasound may play a role in identifying fetal growth acceleration in diabetic pregnancies. Fetal liver volume increase is positively related to maternal HbA1c levels reflecting degree of maternal glycemic control. Fetal liver volume normalised for estimated fetal weight is significantly higher in the fetuses of diabetic women. In the present study, umbilical venous volume flow and fetoplacental downstream impedance are not different between diabetic and normal pregnancies.

Assessment of fetal liver volume and umbilical venous volume flow in pregnancies complicated by insulin-dependent diabetes mellitus

Objectives To determine fetal liver volume and its relation with umbilical venous volume flow and maternal glycosylated haemoglobin (HbA1c) in pregnancies complicated by diabetes mellitus type I. Design A cross sectional matched control study. Setting Obstetric out patient clinic, Erasmus MC—University Medical Centre, Rotterdam. Population Data from fetuses of diabetic women (n = 32; 18–36 weeks) were compared with data from normal controls (n = 32) matched for gestational age. Methods Umbilical venous cross sectional area (mm2) and time-averaged velocity (mm/s Doppler) were determined for calculation of volume flow (mL/min) and flow per kilogram fetal weight (mL/min/kg). Umbilical artery pulsatility index was determined. Fetal liver volume measurements were obtained using a Voluson 530-D. Main outcome measures Fetal liver volume, umbilical venous volume flow and downstream impedance. Results A statistically significant difference between fetuses of diabetic women and normal controls was found for liver volume (mean [SD]: 45.9 [34.0] vs 38.3 [28.7] mL), abdominal circumference (22.2 [6.6] vs 21.3 [5.6] cm), estimated fetal weight (1162 [898] vs 1049 [765] g) and fetoplacental weight ratio (0.22 vs 0.19) and liver volume/estimated fetal weight ratio (4.13% [0.007] vs 3.62% [0.009]). Umbilical venous volume flow (mL/min) and umbilical artery pulsatility index were not essentially different between the two study groups, but umbilical venous volume flow per kilogram fetal weight was lower (P < 0.05) in the diabetes group (94.3 [26.1] mL/min kg) compared with normal controls (109.5 [28.0] mL/min/kg). A positive correlation existed between fetal liver volume and maternal HbA1c (P = 0.002). Conclusions Measurement of fetal liver volume by three-dimensional ultrasound may play a role in identifying fetal growth acceleration in diabetic pregnancies. Fetal liver volume increase is positively related to maternal HbA1c levels reflecting degree of maternal glycemic control. Fetal liver volume normalised for estimated fetal weight is significantly higher in the fetuses of diabetic women. In the present study, umbilical venous volume flow and fetoplacental downstream impedance are not different between diabetic and normal pregnancies.

FETAL VENOUS CIRCULATION

Ultrasound evaluation of the venous system is now a compulsory part of the haemodynamic assessment of the fetus. Once umbilical venous flow was introduced1,2 and its pulsatile pattern discovered in the compromised fetus,3 other sections of the venous system have been added or explored for possible diagnostic use: the inferior and superior vena cava,4,5 ductus venosus,6,7 hepatic veins,8 pulmonary veins,9,10 and intracranial veins.11-13 The following presentation is not intended to be a complete review of the fetal venous circulation, which is growing by the day, but rather to focus on some central issues with an emphasis on physiologic principles. The reason for this focus is that, as clinicians, we tend to work according to pattern recognition, which is a necessary principle in daily life. However, in the long run as the fetal patient increasingly demands a more dynamic approach to solve the diagnostic riddles, we find ourselves digging deeper into the physiological mechanisms behind ultrasound images and recordings.

P068: Umbilical venous volume flow and fetal behavioural states in the normally developing fetus

P068: Umbilical venous volume flow and fetal behavioural states in the normally developing fetus

Measurement of volume flow by "colour velocity imaging (CVI)": technique of measurement in the intrahepatic fetal umbilical vein

"Colour Velocity Imaging (CVI)" permits acquisition of ultrasound Doppler data for quantitative analysis. CVI can be used to study the fetal circulation. In a pilot study we attempted measuring umbilical venous flow. Data acquisition is simple and fast. In the current implementation, data is sent to a work-station and analysed off-line. There is significant "intra-observer-variability" that could be attributable to true physiological variation or measurement inaccuracies. Measurement of fetal umbilical volume flow by CVI is a new and simple technique. Before its clinical use assumptions about the vessel, flow, variability and normal values must be verified in the fetus.

The role of intraplacental vascular smooth muscle in the dynamic placenta: a conceptual framework for understanding uteroplacental disease

Although non-innervated, the placenta must continually accommodate changes in uteroplacental pressure (due to spiral artery failure, maternal position, maternal emotional state, etc.), which might otherwise be expected to result in rapid feto–maternal water fluxes in the highly water-permeable human hemochorial placenta. Uteroplacental flow must also be under the same influences, producing temporary, or permanent, regions of poor intervillous flow, yet the reduction of umbilical vein oxygen content that would be expected to be produced by such shunts of feto–placental blood do not occur in the normal fetus. We suggest that there is a local villus tree mechanism matching intravillus flow of fetal blood to local uteroplacental oxygen content. By analogy to ventilation/perfusion (V/Q) matching in the postnatal lung we suggest the term U/Q matching for this mechanism in the placenta. We further suggest that such disturbances in flow matching are compensated for by the fetus, via complementary adjustment of umbilico-chorionic artery and umbilical venous flow resistances, utilizing the differing sensitivities of vascular smooth muscle tissues of embryonic and extra-embryonic origin to vasoactive agents.

Doppler velocimetry for predicting fetal death in a twin pregnancy

Doppler velocimetry for predicting fetal death in a twin pregnancy

Serial sonographic findings of four fetuses with homozygous alpha‐thalassemia‐1 from 21 weeks onwards

To evaluate the potential usefulness of noninvasive ultrasound assessment of fetal anemia in the diagnosis and management of fetuses with homozygous alpha-thalassemia-1. We describe four pregnancies complicated by fetal homozygous alpha-thalassemia-1. They presented with ultrasound abnormalities before the development of hydrops. As part of evaluating the fetal condition, we performed ultrasound and Doppler studies aimed at identifying fetal anemia. These studies included evaluation of intrahepatic umbilical venous maximum flow velocity, middle cerebral artery peak flow velocity, fetal liver length and spleen perimeter. In all four fetuses, ultrasound and Doppler studies suggested the presence of fetal anemia. Homozygous alpha-thalassemia-1 was diagnosed in all cases, with fetal blood sampling confirming anemia in three fetuses. The majority of the intrahepatic umbilical venous maximum flow velocity and middle cerebral artery peak flow velocity measurements were above the 95th centile. Two fetuses underwent intrauterine transfusion and fetal blood flow velocities returned to normal after correction of the fetal anemia. The fetal liver length and spleen perimeter measurements showed a similar trend, although they were less consistent before 28 weeks. Non-invasive ultrasound parameters, in particular quantification of intrahepatic umbilical venous maximum flow velocity and middle cerebral artery peak flow velocity, were found to be useful in the diagnosis and management of fetal anemia in pregnancies with fetal homozygous alpha-thalassemia-1.

Doppler investigation in intrauterine growth restriction--from qualitative indices to flow measurements: a review of the experience of a collaborative group.

In 1997 we started a collaboration among three groups, combining our experience with Doppler examination of the human fetus, blood flow studies on fetal lamb, and mathematical modeling of human circulation. In preliminary investigations on fetal lambs, the same Doppler method designed for the human fetus was used to measure venous blood flow in the umbilical veins of seven fetal lambs. Doppler measurements and diffusion technique groups for umbilical venous flow were 210.8+/-18.8 and 205.7+/-38.5 ml/min/kg, respectively (p = 0.881). In human pregnancy the interobserver variabilities for the vein diameter, mean velocity, and absolute umbilical venous blood were 2.9%, 7.9%, and 12.7%, respectively. A cross-sectional study allowed us to establish normal reference values. Venous blood flow/kg of estimated fetal weight showed a nonsignificant linear reduction with gestational age, from 128.7 ml/min/kg at 20 weeks to 104.2 ml/min/kg at 38 weeks. In a series of 37 growth-restricted fetuses, the UV flow per kilogram was significantly lower in the more severe growth-restricted fetuses (abdominal circumference below the second percentile and abnormal umbilical arterial p.i.) than in normal comparable fetuses (p < 0.001). In a series of 140 normal fetuses, we calculated that the absolute blood flow rate in the ductus venosus (DV) increases significantly with advancing gestational age from 20 to 38 weeks of gestation (from 23.2+/-9.6 ml/min to 43.5+/-21.5 ml/min). This means that the percentage of umbilical blood flow shunted through the DV decreases significantly during gestation (from 50% at midgestation to 20% at 38 weeks). In a series of 45 growthrestricted fetuses, delivered because of nonreactive fetal heart rate (group 2) and for other reasons but still with a normal heart rate pattern (group 1), we measured the ductal inlet diameter. In these fetuses, the diameters at the ductal isthmus, normalized for the dimension of the abdominal circumference (inlet diameter/abdominal circumference), were significantly larger (group 1 = 6.8+/-2.3; group 29.4+/-2.8 ) than in the control group (6.1+/-0.3). This means that in this subset of fetuses the amount of blood shunted can be increased as a compensatory mechanism.

Flow in an Elastic Tube Subject to Prescribed Forcing: A Model of Umbilical Venous Flow

We investigate the fluid flow through a finite length, axisymmetric tube when the elastic wall is subject to either a prescribed external pressure or a prescribed motion. The prescribed wall forcing is assumed to consist of a forward travelling wave together with a reflected travelling wave. The dimensionless diameter variation of the tube is taken to be small and perturbation techniques are used to solve the weakly non‐linear problem. Particular attention is given to the steady streaming flow that is induced through the non‐linear convective acceleration terms. The results are applied to the flow of blood in the umbilical vein (UV), which has important physiological implications.

Flow in an Elastic Tube Subject to Prescribed Forcing: A Model of Umbilical Venous Flow

We investigate the fluid flow through a finite length, axisymmetric tube when the elastic wall is subject to either a prescribed external pressure or a prescribed motion. The prescribed wall forcing is assumed to consist of a forward travelling wave together with a reflected travelling wave. The dimensionless diameter variation of the tube is taken to be small and perturbation techniques are used to solve the weakly non-linear problem. Particular attention is given to the steady streaming flow that is induced through the non-linear convective acceleration terms. The results are applied to the flow of blood in the umbilical vein (UV), which has important physiological implications.

Invasive versus non-invasive testing in red-cell alloimmunized pregnancies

Amniocentesis for amniotic fluid bilirubin levels is the most widely used test to predict the severity of fetal disease in red-cell alloimmunization. Many textbooks and guidelines recommend serial amniocentesis to monitor these pregnancies. However, the reliability of amniotic fluid bilirubin measurements has been questioned. Two strategies have been proposed by investigators. Some advocate liberal or primary use of fetal blood sampling, while others promote the use of non-invasive ultrasonography and Doppler. The purpose of this literature review is to examine the usefulness of amniocentesis, ultrasonography and Doppler to predict the degree of fetal hemolytic anemia. The evidence suggests that amniotic fluid bilirubin measurements are of limited value in the second trimester. Furthermore, critical appraisal of the very few prospective studies is hampered by limitations in design or insufficient data given by the authors. Many ultrasound and Doppler parameters have been proposed as useful indicators of fetal anemia. The most promising of these methods are Doppler assessment of umbilical venous and middle cerebral artery flow velocities. We speculate that the accuracy of these non-invasive tests may be good enough to incorporate them in management protocols, possibly replacing amniocentesis. Well-designed prospective studies are needed to prove this hypothesis.

Changes in umbilical venous velocities with physiologic perturbations

Objective: The purpose of this study was to determine the direction of transmission of umbilical venous Doppler flow velocity changes in human fetuses. Study Design: Strip chart recordings of simultaneously measured umbilical arterial and venous velocities were examined at two sites in the umbilical cord, one near the fetus (proximal) and one near the placenta (distal). Fetuses with venous pulsations or breathing episodes were included. At both locations time from venous pulsation to arterial systole was measured in fetuses with venous pulsations and duration of phase delay between arterial diastolic velocity minimum and venous velocity minimum was measured in fetuses with breathing episodes. Results: In 21 fetuses with venous pulsations the pulsations occurred earlier in the cardiac cycle at proximal sites (0.12 ± 0.04 second before systole) and later at distal sites (0.02 ± 0.04 second before systole; P < .001). Phase delays in venous velocities in the 5 fetuses with breathing episodes were also longer at distal sites than at proximal sites ( P < .011). Conclusion: Changes in umbilical venous velocities occurred earlier at sites that were closer to the fetus. These findings suggest that changes in umbilical venous velocities originate in the fetal venous system and are transmitted to, rather than from, the placenta. (Am J Obstet Gynecol 2000;182:835-40.)

Assessment of umbilical arterial and venous flow using color Doppler

To estimate the umbilical artery and vein blood volume flow using B-mode and Doppler ultrasound in the second and third trimesters of pregnancy. This was a cross-sectional study of 129 singleton, healthy pregnancies at 23-33 weeks' gestation. The umbilical artery and vein cross-sectional area, time-averaged velocity and pulsatility index were measured in a free loop of cord, and the fetal weight was estimated. Ranges for each parameter were obtained; from these the blood flow for the vein and artery was calculated, and the average flow corrected for fetal weight was derived. The median time for examination was 6 min. The mean cross-sectional area and time-averaged velocity for both the vein and artery increased linearly with gestation. The umbilical artery flow correlated closely with the average vein flow (r = 0.9, p < 0.001). There was a significant, though poor, inverse correlation between the umbilical artery pulsatility index and the average umbilical flow (r = -0.25, p < 0.05). The average umbilical flow (calculated from the mean of arterial and venous flow), corrected for estimated fetal weight, decreased from 189.2 ml/kg per min at 23 weeks to 176.2 ml/kg per min at 33 weeks' gestation. The estimates of fetal umbilical flow obtained by this Doppler method are consistent with previously published data. Averaging the arterial and venous flow is theoretically advantageous in reducing the inherent errors in estimating either the arterial or the venous flow. This method of measuring umbilical flow may have clinical potential in assessing fetal health and disease processes.

Association between a low umbilical artery pulsatility index and fetal distress in labor in very prolonged pregnancies

Objective: To investigate the association between fetal, umbilical and uterine circulatory changes and adverse perinatal findings in very prolonged pregnancies. Study design: 44 women proceeding to 43 completed weeks of gestation with the intention of a trial of vaginal delivery were studied prospectively with ultrasound Doppler velocimetry. An intensified fetal surveillance was routinely commenced at 42 weeks and only uncomplicated pregnancies were allowed to proceed. The endpoint perinatal measures were oligohydramnios, fetal meconium release, fetal distress in labor and birth asphyxia. Flow variables in different groups were compared with the Mann-Whitney U test, Student's unpaired t-test, Wilcoxon signed-rank matched-pairs test. Fisher's exact test and contingency table analysis, and a two-tailed P value < 0.05 was considered statistically significant. Results: The umbilical artery pulsatility index was significantly lower in cases of fetal meconium release ( n = 12) and fetal distress ( n = 7). The umbilical venous flow velocity was significantly lower in cases of meconium, and the fetal aortic volume flow significantly higher in cases of fetal distress. No significant flow changes were found in connection with oligohydramnios ( n = 5) and birth asphyxia ( n = 2). Uterine flow was not significantly affected in any group. Conclusions: In very prolonged pregnancies, fetal distress in labor was not associated with an increased placental vascular resistance. In contrast to previous reports, the umbilical artery pulsatility index was low in cases of fetal distress and meconium release. The etiology is unknown, but a subclinical fetal hypoxia might have triggered a vasodilation of placental vessels. Vasodilation at an unchanged volume flow could also explain the decrease of umbilical venous flow velocity. The increased aortic volume flow indicates an increase of cardiac output in fetuses later developing distress in labor.

Evaluation of umbilical venous blood flow by Doppler color flow mapping and conventional ultrasonographic methods.

Ultrasonographic measurement of umbilical venous blood flow as a reflection of placental blood flow has been used for assessment of fetal well-being. Because fetal and maternal factors may prevent satisfactory measurement of umbilical venous diameter and flow velocity, an alternative method would be helpful. We found that, in 35 human fetuses between 18 and 35 weeks of gestation, that both variables for umbilical venous flow calculation can be measured from a single Doppler color frame with close measurement agreement to conventional combined cross-sectional pulsed Doppler ultrasonographic measurements. Thus, this method provides an alternative to the conventional method or may be used for a cross-check and has the potential for automated flow calculation.

The significance of high umbilical venous blood flow measurements in a high-risk population.

We report a statistical analysis of 893 high-risk patients who underwent Doppler sonographic estimation of umbilical venous blood flow within 2 weeks of delivery. Patients with red cell isoimmunization were excluded. In a total of 84 patients, the umbilical venous flow rate was above the 95th centile for normal pregnancy. This finding was associated significantly with an increased prevalence of maternal diabetes mellitus, polyhydramnios, fetal abnormalities, premature delivery, low 5 min Apgar scores, and neonatal death. Umbilical venous flow rates per kilogram of fetal weight above the 95th centile were recorded in 93 patients. This finding was associated significantly with an increased rate of antepartum hemorrhage, premature delivery, low 5 min Apgar scores, longer stays in intensive care nursery, and neonatal death. Low umbilical venous blood flow rates have been investigated extensively and associated with impaired perinatal outcome. The work reported in this paper indicates that a percentage of fetuses will have abnormally high umbilical venous flow rates and that this is also indicative of increased risk.

Doppler color flow mapping permits easier and faster measurement of umbilical venous flow than does 2D-ultrasound combined with pulsed Doppler

Doppler color flow mapping permits easier and faster measurement of umbilical venous flow than does 2D-ultrasound combined with pulsed Doppler