Venous Flow Velocity Waveforms Research Articles

Evaluation of Fetal Pulmonary Veins During Early Gestation by Pulsed Doppler Ultrasound: A Feasibility Study

AbstractCongenital heart disease (CHD) is the leading cause of infant mortality. Nevertheless, routine prenatal ultrasound only detects 30 %–50 % of CHD cases. Therefore, emphasis should be placed on early predictors of CHD that allow physicians to timely refer high-risk patient to specialized fetal echocardiography, in order to maximize chances of improved outcomes. The fetal venous system has been the focus of attention as a marker of heart function. Yet, there exist inconsistent data about the acquisition of pulmonary venous flow in early pregnancy. This study aims to determine the feasibility of fetal pulmonary venous flow acquisition in early pregnancy, and the association between pulmonary vein (A-wave) flow reversal and the presence of CHD. Total of 211 consecutive pregnant women, between 12 and 15 weeks of gestation, underwent routine obstetric ultrasound along with basic fetal echocardiography including fetal pulmonary venous flow assessment. The pulmonary venous flow velocity waveforms were acquired by either Doppler or Doppler plus enhance flow technique based on equipment availability. All the cases were re-evaluated by specialized fetal echocardiography during late pregnancy to identify congenital heart anomalies. The acquisition of fetal pulmonary vein, between 12 and 15 weeks of gestation, was successfully accomplished in 87.7 % of cases. Five out of seven fetuses with end-diastolic (A-wave) pulmonary venous flow reversal were associated with confirmed cardiac anomaly. In this pilot study, pulmonary venous (A-wave) flow reversal was associated with cardiac anomalies in 86.8 % of cases (p = 0.001). This pilot study proposes that Doppler interrogation of fetal pulmonary vein flow during early pregnancy is feasible. Furthermore, the presence of pulmonary vein (A-wave) reversal might represent a marker of major cardiac anomalies. Further investigation is needed to confirm these findings.

Discordance of arterial and venous flow velocity waveforms in severe placenta‐based fetal growth restriction

Balancing iatrogenic prematurity against stillbirth due to terminal placental dysfunction poses a crucial dilemma in the management of severe fetal growth restriction (FGR). The role of multivessel Doppler assessment in defining severity and progression is clear, but gestational age at delivery remains the single most important factor when FGR is severe and early onset1. Recently, Diemert and Hecher2 reported FGR cases where venous Doppler indices may have called for delivery, but pregnancy was extended because arterial indices were not so abnormal. Is this discordance a rare curiosity, or a significant caution to the Doppler-based management of FGR? We were prompted by this question to analyze our collaborative database of 604 FGR cases3, 4. A manual of standard imaging and measurement techniques was distributed. Collaborating centers demonstrated concordance with these techniques, including submission of representative images to the principal author (A.A.B.). Inter-center variation for Doppler parameters and primary outcomes was analyzed to test relative uniformity of participating centers. Further detailed analysis of group vs. individual performance statistics and center-by-center contribution to mortality and morbidity was completed to ensure that results could be reliably grouped3. We defined significant discordance between arterial and venous (A/V) Doppler in two ways: Categorical definition: for patients with positive end-diastolic velocity (PEDV) in the umbilical artery (UA), absence or reversal of the ductus venosus a-wave (DV-RAV) was considered to be significantly A/V discordant (analogous to the cases presented by Diemert and Hecher2). When UA Doppler showed absent or reversed end-diastolic velocity (A/REDV), we reasoned that there would be no clinical difference between antegrade DV a-wave and DV-RAV, so categorical definition did not apply; Numerical definition: since the UA and DV pulsatility indices (PI) can be calculated regardless of end-diastolic velocity, significant discordance was also denoted if a Z-score difference > 2 was present when DV-PI Z-score was compared with UA-PI Z-score. Fifty-four of 604 fetuses (8.9%) had significant A/V discordance of the Doppler parameters. Thirty-four of these had major complications and 23 died during the neonatal period (all, chi-square P < 0.0001 compared with FGR fetuses with concordant A/V measures). Since many experienced major morbidity and ultimately died, cases may be recorded in both adverse outcome groups. Intact survivors numbered 17, 4/15 (26.7%) in the PEDV group and 13/39 (33.3%) in the A/REDV group. Outcomes for fetuses stratified by UA end-diastolic velocity are displayed in Table 1. Within both subgroups, UA cord pH and the amniotic fluid index were significantly lower in patients with disproportionally worse DV Doppler parameters, while gestational ages at delivery did not differ. Discordance of DV and UA Doppler parameters is observed in a smaller proportion of fetuses with positive UA end-diastolic velocity compared to fetuses with A/REDV. While disproportional worsening of DV parameters in A/REDV fetuses is a well-described response to worsening placental dysfunction this observation is less well defined in patients with positive UA end-diastolic velocity. Irrespective of UA end-diastolic category, discordant deterioration of the DV Doppler parameters is associated with worse outcome in neonates with preterm FGR. This appears to be related to fetal deterioration rather than gestational age as illustrated by the lower pH and amniotic fluid parameters. A minority of patients with A/V discordance have normal outcome, but these are important because if timing of delivery is determined by DV parameters alone, 30% of patients with PEDV and up to 50% of patients with A/REDV may be delivered earlier than necessary. The TRUFFLE study4 may answer many questions regarding the neurodevelopmental impacts of delivery triggers based on the DV and computerized cardiotocography. However, the cases presented by Diemert and Hecher2 and our analysis suggest that discordance of Doppler deterioration and outcome may be a significant confounder—additional fetal variables may be important. The discriminatory role of amniotic fluid assessment as one of the biophysical parameters suggests the merit of further evaluation of integrated fetal testing in the context of FGR management1. A. A. Baschat*, C. R. Harman*, * Department of Obstetrics, Gynecology and Reproductive Sciences, University of Maryland School of Medicine, Baltimore, MD, USA

Antepartum fetal testing: a critical appraisal

Recognition of the fetus at risk for death or damage in utero, quantifying the risk, balancing fetal risk against the risk of neonatal complications from immaturity and determining optimal time and mode of intervention, is a cornerstone of modern perinatal medicine. Antepartum fetal testing is essential in making these crucial decisions. The art and science of fetal assessment is fluid. In this treatise, the evolution of testing is reviewed, test accuracy results examined and suggestions for future applications are considered. Composite testing of a range of fetal biophysical variables is an excellent predictor of fetal acidemia and risk of death or damage. Confusion regarding the optimal means of measuring one of these variables, amniotic fluid volume, has been addressed in the literature and contemporary studies from several independent sources indicate that the amniotic fluid index method should be abandoned in favor of the maximal vertical pocket method. It is becoming increasingly more evident that a spectrum of fetal testing modalities based on interrogation of different aspects of fetal adaptive responses to adversity is preferable in fetal testing. Further it is evident that in some fetal diseases, such as intrauterine growth restriction, fetal condition may change acutely and accordingly best outcome is achieved by much more frequent testing. The question of whether intervention for fetal compromise can prevent subsequent neurological sequelae remains open. There has been remarkable advancement in identifying the fetus at risk. The concept of multispectral combined fetal testing including acute biophysical variables, amniotic fluid volume and arterial and venous Doppler flow velocity waveforms is established.

Venous Doppler in the assessment of fetal cardiovascular status

The purpose of this review is to highlight recent developments in the Doppler assessment of the fetal venous circulation with special reference to clinical applications in the human fetus. Doppler evaluation of the fetal venous circulation has increased our understanding of fetal cardiovascular function. Examples include the regulatory role of the ductus venosus in fetal nutrient partitioning and the significance of venous and arterial circulatory watershed areas. Alterations in cardiac afterload, contractility compliance, intravascular volume status and heart rate modulate venous and arterial flow velocity waveforms. Concurrent examination of these cardiovascular factors is of great importance in fetal growth restriction, complicated monochorionic multiple gestation, fetal hydrops and arrhythmia. In these conditions, comprehensive Doppler assessment provides critical diagnostic and prognostic information and has a key role in directing interventions. Venous Doppler has added a critical dimension to the understanding of fetal cardiovascular pathophysiology. In both health and disease, venous Doppler must now occupy a fundamental position in the comprehensive assessment of the fetal circulation.

Effect of antenatal glucocorticoid therapy on arterial and venous blood flow velocity waveforms in severely growth-restricted fetuses.

To study the effects of antenatal glucocorticoid (betamethasone) therapy on blood flow velocity waveform patterns in the umbilical artery (UA), middle cerebral artery (MCA) and ductus venosus (DV) in severely intrauterine growth-restricted (IUGR) fetuses. Fifty-five severely IUGR fetuses at 24-34 weeks of gestation were included in the study. The effect of antenatal glucocorticoid administration on Doppler findings in the UA, MCA and DV was studied using two statistical approaches, namely paired sample analysis and multilevel analysis. There were no effects of betamethasone on the pulsatility index (PI) of the vessels studied. The only changes noticed during the 14 days of observation were a gradual decrease of PI in the MCA, an increase in the UA-PI/MCA-PI ratio and an increase in the DV-PI. These changes with time may be explained by a progressive and gradual deterioration of the fetal condition. Antenatal glucocorticoids (betamethasone) do not affect fetal Doppler waveform patterns of the UA, MCA and DV in severely IUGR fetuses.

Reference values of fetal ductus venosus, inferior vena cava and hepatic vein blood flow velocities and waveform indices during the second and third trimester of pregnancy.

Our objective was to establish reference values for ductus venosus, inferior vena cava and hepatic vein flow velocities during ventricular systole (S-wave) and diastole (D-wave), the lowest forward velocity during atrial contraction (a-wave), the intensity-weighted mean flow velocity (Vmean) and different calculated indices. Venous flow velocity waveforms were obtained from 329 singleton pregnancies at 20-42 weeks of gestation by pulsed-wave color Doppler. Reference values were constructed by means of a quadratic regression model after logarithmic transformation of original data. With advancing gestational age the peak velocity index for the vein (PVIV) and pulsatility index for the vein (PIV) decreased whereas blood flow velocities increased. Blood flow velocities were highest in the ductus venosus and lowest in the right hepatic vein. Values for PVIV and PIV were highest in the hepatic vein and lowest in the ductus venosus. During atrial contraction there was a blood flow towards the fetal heart in the ductus venosus, whereas in the inferior vena cava and in the hepatic vein blood flow was either in the opposite from the fetal heart (reverse flow), or there was absent flow (zero flow) or flow was towards the fetal heart (positive flow). The reference ranges and calculated velocities established in this study may be utilized in studies dealing with the role of ductus venosus and inferior vena cava blood flow in fetuses with chromosomal abnormalities or congenital heart disease as well as hypoxic conditions. We speculate, that the reduction in PVIV and PIV with advancing gestational age may reflect a decrease in cardiac afterload as a result of maturation of diastolic ventricular function.

WS12‐08Pulmonary arterial and venous flow velocity waveforms in growth restricted fetuses

ObjectiveTo measure peripheral pulmonary artery (PPA) and pulmonary vein (PV) velocity waveforms in growth restricted fetuses (IUGR) and to relate them to different Doppler indices fetal circulation and to pregnancy outcome.Design and methods108 IUGR fetuses from singleton pregnancies (gestational age median 28.4 range 25–32) were prospectively considered for this study. Entry criteria were an ultrasonographic extimated fetal weight &lt; 5th centile, the absence of structural and chromosomal abnormalities, and a Pulsatility Index (PI) in umbilical artery &gt; 95th centile of our reference limits for gestation. Velocity waveforms were recorded from the PPA and in one of the PV in proximity of the inflow in the left atrium. The PI from PPA and the Pulsatility Index for the vein from PV (PIV = [S − D]/m) were calculated. Values obtained were compared to our reference limits for gestation and related to other Doppler indices from arterial, cardiac and systemic venous circulation and to fetal outcome.ResultsIn IUGR fetuses both the PI from PPA (P &lt; 0.001) and the PIV from the PV (P &lt; 0.001) were increased when compared to control fetuses. An inverse relationship was found between PPA and middle cerebral artery PI. Changes in PV were present when abnormal velocity waveforms are present in the systemic venous circulation. Reverse flow during atrial contraction is present in pulmonary vein in the most severely compromised fetuses and are associated with fetal distress and imminent fetal death.ConclusionsAbnormalities in arterial and pulmonary flows are present in IUGR fetuses. Changes in arterial circulation occur at an early stage of the disease while modifications in venous flows occurs later and may be the expression of an impaired function of the left ventricle close to fetal jeopardize.

Coronary artery blood flow visualization signifies hemodynamic deterioration in growth‐restricted fetuses

To determine the relationship between fetal coronary blood flow (CBF) visualization in intrauterine growth restriction (IUGR), longitudinal changes in arterial and venous flow velocity waveforms and perinatal outcome. A total of 48 IUGR fetuses (abdominal circumference below the 5th percentile for gestational age) with absent or reversed umbilical artery (UA) end-diastolic velocity (AREDV) were examined longitudinally by echocardiography attempting CBF visualization at each examination. Doppler evaluation of the middle cerebral artery, inferior vena cava (IVC), ductus venosus (DV) and umbilical vein (UV) was performed at each examination. Doppler measurements were correct for gestational age by conversion into Z-scores (delta-indices). Doppler results and outcome from fetuses in which CBF was visualized (group 1, n = 20) and those in which CBF was never visualized (group 2, n = 28) were compared. Outcome parameters analyzed included Apgar scores, cord arterial blood gases, perinatal mortality, respiratory distress, bronchopulmonary dysplasia, intraventricular hemorrhage, necrotizing enterocolitis and postpartum circulatory failure requiring pressor support. There was no difference in Doppler indices between groups at study entry. CBF visualization coincides with a significant increase of UA-, IVC- and DV delta-indices. The greatest rate of change was observed for indices in the ductus venosus which occurred in the 24 h preceding CBF visualization. Group 1 fetuses required earlier delivery (median 27 + 4, vs. median 30 + 0), had lower birthweight (682 +/- 305 g vs. 936 +/- 416 g), lower cord pH (7.21 +/- 0.1 vs. 7.27 +/- 0.06) and cord pO2 (13 +/- 4.5 vs. 24.1 +/- 13.5 mmHg) compared to group 2 (all values P < 0.05). Mortality was similar (group 1 = 6/20, 30%; group 2 = 6/28, 21.4%). In IUGR, fetuses with AREDV and centralization are at high risk for hypoxemia, acidemia and adverse outcome. CBF visualization coincides with deteriorating venous flows. Operator dependence of CBF visualization and the strong association with abnormal venous flow stresses the importance of venous Doppler surveillance in these fetuses.

P98Effects of maternal betamethasone administration on fetal Doppler flow velocity waveforms

BackgroundTo investigate the effect of maternal betamethasone administration on fetal arterial, venous and cardiac Doppler flow velocity waveforms.Method Patients: 13 women with singleton pregnancies considered at risk of preterm labour received an intravenous dosis of 2 × 8 mg betamethasone. Study design: Prospective study. Main outcome measures: Doppler studies were performed from the umbilical artery, middle cerebral artery, both uterine arteries, from the ductus venosus, inferior vena cava, right hepatic vein, form the av‐valves, right and left ventricular outflow tract and the ductus arteriosus before and after (30 min, 24, 48 and 72 h) betamethasone administration. Peak systolic velocities and maximum end‐diastolic velocities were recorded. Calculation of the resistance index (RI) for the arterial system, the peak velocity index for veins (PVIV) for the venous system and the E/A ratio for the av‐valves.ResultsNo significant variation was noted in the Doppler measurements before and after betamethasone administration. A slight and reversible increase of the peak systolic velocity of the ductus arteriosus and the right ventricular outflow tract was observed at 30 min after betamethasone administration.ConclusionBetamethasone administration does not cause a significant change of the arterial, venous and intracardiac Doppler flow velocity waveforms in healthy fetuses.

F125Fetal pulmonary venous Doppler flow velocity waveforms in congenital heart defects

Aim of the studyis to analyze blood flow velocity waveforms (FVW) in the pulmonary veins using pulsed Doppler ultrasound in fetuses with a prenatally detected congenital heart defect (CHD).MethodsIn 96 fetuses with various CHD Doppler FVW from the pulmonary veins were assessed. Gestational age varied between 18 and 38 weeks. Following Doppler parameters were analyzed and compared to reference ranges: systolic (S), diastolic (D) peak velocity, end‐diastolic velocity during atrial contraction (A), peak velocity index for veins (PVIV) and Pulsatility Index for veins (PIV).ResultsWe could distinguish 5 different patterns of FVW reflecting different stages of pulsatility and preload within the left atrium. Abnormal patterns were mainly observed in fetuses with left atrial obstruction and a restrictive foramen ovale having a reversed A‐wave as well as in mitral regurgitation.ConclusionsAbnormal FVW in fetal cardiac defects depend from the left atrial pressure rather than on the cardiac defect itself. Patterns of FVW can help in quick differentiation of increased interatrial pressure, which can impair early neonatal outcome.

F59Fetal venous Doppler in the normal first and second stage of labor

BackgroundThe aim of the study was to evaluate, whether differences in fetal venous flow velocity waveforms can be seen in fetuses during labor compared to fetuses before labor.MethodThe Pulsatility index for veins (PIV) of the ductus venosus was analysed in 127 fetuses (37th to 41th weeks) before labor by color Doppler sonography (control group). Identically 42 fetuses with normal cardiotocogram were analysed during and between contractions consecutively in the early first stage of labor, at 2–4 cm and 6–8 cm and at full dilatation of the cervix (study group).ResultsThe control group showed a normal PIV of 0.59 (SD 0.24). In the study group between contractions the PIV was normal during all stages of labor with average values of 0.55 − 0.68 (SD 0.26 − 0.42). During contraction the average values of the PIV were 1.64 – 2.48 (SD 0.76 – 1.16). These values were significant elevated (P &lt; 0.001) during contraction compared to the values of contraction free episodes as well as to the control group. The increase of the PIV during contractions was not related to any fetal heart rate deceleration.ConclusionDuring contractions the fetal venous pressure is significantly elevated in normal labor. Reference ranges for the ductus venosus should be established and compared to values in compromised fetuses.

Internal jugular vein blood flow in normal and growth-restricted fetuses

Objective: To assess internal jugular vein blood flow patterns during the second half of pregnancy in normal and growth-restricted fetuses. Methods: We did Doppler ultrasound studies of internal jugular veins and the inferior vena cavas longitudinally on 21 normal singleton fetuses from 20 weeks to term, and on eight growth-restricted fetuses with absent end-diastolic flow at the umbilical artery (UA). The three components of the venous flow velocity waveforms were used to calculate peak velocity ratio: Peak systolic velocity (S wave) minus reverse peak velocity (R wave) divided by peak velocity during early diastole (D wave) and velocity time integral ratio: systolic velocity time integral minus reverse velocity time integral divided by velocity time integral during early diastole. Statistical analysis of longitudinal measurements used K-related samples Friedman test; groups were compared with Mann-Whitney U test and χ 2 test. Results: In normal fetuses we found significant increases in peak velocity ratio and velocity time integral ratio of internal jugular veins and the inferior vena cavas throughout gestation. The mean ± standard deviation (SD) of the internal jugular veins peak velocity ratio (1.12 ± 0.4 versus 1.46 ± 0.15, P < .05) and velocity time integral ratio (1.1 ± 0.2 versus 1.55 ± 0.17, P < .05) were significantly lower in growth-restricted fetuses compared with normal fetuses at 28–32 weeks’ gestation but inferior vena cava indices were not. None of the eight growth-restricted fetuses had umbilical venous pulsations or changes in inferior vena cava or ductus venosus blood flow patterns. All had arterial pH above 7.15 at birth. Conclusion: Growth-restricted fetuses with absent end-diastolic velocity in the UA have changes in internal jugular vein blood flow patterns that probably indicate increased cerebral blood flow, more evidence of redistribution of blood flow in growth-restricted fetuses that can be used to maintain them.

Behavior-State–Dependent Changes in Human Fetal Pulmonary Blood Flow Velocity Waveforms

In Brief Objective To establish the influence of fetal behavior states on venous and arterial pulmonary blood flow velocity waveforms in the normally developing term fetus. Methods The relation between venous and arterial pulmonary blood flow velocity waveforms and fetal behavior states was investigated in 18 normal term fetuses. Recordings of the venous pulmonary blood flow velocity waveforms were obtained just proximal to the entrance in the left atrium, and the arterial pulmonary blood flow velocity waveforms were taken from the most proximal branch of the pulmonary artery in the same lung using color Doppler imaging. Time-averaged peak systolic, peak diastolic, and end-diastolic flow velocity; peak systolic to peak diastolic ratio; pulsatility index; and fetal heart rate were calculated from both venous and arterial Doppler recordings obtained during behavior states 1F (quiet sleep) and 2F (active sleep). Fetal behavior states were determined from combined recordings of fetal eye and body movements. Results Recordings of sufficient quality for analysis were obtained from ten fetuses. Venous pulmonary blood flow velocity waveforms demonstrated a statistically significant increase in time-averaged peak diastolic and end-diastolic velocity during fetal behavior state 2F. No behavior-state-related changes were observed for the arterial pulmonary blood flow velocity waveform. Conclusion The data suggest an increased pressure gradient between the pulmonary venous system and the left atrium during behavior state 2F. Flow velocity waveforms from the proximal arterial pulmonary branch are independent of behavioral state. Doppler velocity waveform analysis demonstrates behavior-state dependency in the venous pulmonary system but not in the arterial pulmonary system in the term fetus.

Behavior-state–dependent changes in human fetal pulmonary blood flow velocity waveforms

Objective: To establish the influence of fetal behavior states on venous and arterial pulmonary blood flow velocity waveforms in the normally developing term fetus. Methods: The relation between venous and arterial pulmonary blood flow velocity waveforms and fetal behavior states was investigated in 18 normal term fetuses. Recordings of the venous pulmonary blood flow velocity waveforms were obtained just proximal to the entrance in the left atrium, and the arterial pulmonary blood flow velocity waveforms were taken from the most proximal branch of the pulmonary artery in the same lung using color Doppler imaging. Time-averaged peak systolic, peak diastolic, and end-diastolic flow velocity; peak systolic to peak diastolic ratio; pulsatility index; and fetal heart rate were calculated from both venous and arterial Doppler recordings obtained during behavior states 1F (quiet sleep) and 2F (active sleep). Fetal behavior states were determined from combined recordings of fetal eye and body movements. Results: Recordings of sufficient quality for analysis were obtained from ten fetuses. Venous pulmonary blood flow velocity waveforms demonstrated a statistically significant increase in time-averaged peak diastolic and end-diastolic velocity during fetal behavior state 2F. No behavior-state-related changes were observed for the arterial pulmonary blood flow velocity waveform. Conclusion: The data suggest an increased pressure gradient between the pulmonary venous system and the left atrium during behavior state 2F. Flow velocity waveforms from the proximal arterial pulmonary branch are independent of behavioral state.

Jugular venous blood flow velocity waveforms in human fetuses between 20 and 42 weeks of pregnancy.

The goal of the study was to measure the blood flow parameters of the fetal internal jugular vein during the second half of normal pregnancy using Doppler ultrasound. Jugular blood flow was analyzed in 95 normal singleton fetuses between 20 and 42 weeks gestation. Color and pulsed Doppler ultrasound was used to obtain jugular venous waveforms at the level of the mid-neck. Peak velocities, ratios of velocities, and time-averaged maximum velocities were measured. Jugular venous waveforms in healthy fetuses consist of three phases--the first forward peak occurs during ventricle systole; the second forward peak occurs during early diastole and the third peak occurs during atrial contraction. Forty-eight percent of the fetuses demonstrated absent flow during atrial contraction; 32% of fetuses demonstrated forward flow during atrial contraction and finally 20% of fetuses demonstrated flow reversal during atrial contraction. The reported jugular venous profile may serve as a foundation for future studies of jugular blood flow in high risk fetuses.

Demonstration of fetal coronary blood flow by Doppler ultrasound in relation to arterial and venous flow velocity waveforms and perinatal outcome--the 'heart-sparing effect'.

This longitudinal observational study evaluates the stage at which coronary flow can be visualized by color-coded and pulsed wave Doppler sonography in fetuses with normal cardiac anatomy. Fetal biometry, echocardiography and Doppler examination of the umbilical and middle cerebral arteries, ductus venosus, inferior vena cava and umbilical vein were performed in 109 cases. Fetuses were divided into five groups based on the Doppler examination of the umbilical artery, birth weight and the ability to visualize coronary blood flow. Coronary blood flow was identified in six of 55 fetuses with normal growth who had normal Doppler studies and perinatal outcome. In these, visualization of coronary blood flow was possible after 31 weeks' gestation at a median gestational age of 37 weeks. Coronary blood flow was also visualized in ten of 54 fetuses with severe intrauterine growth retardation and highly pathological flow velocity waveforms in all vessels soon after a significant increase of venous indices in the inferior vena cava and ductus venosus. In these cases, coronary blood flow was identified at a significantly earlier gestational age (median 27 weeks). These fetuses had a poor perinatal outcome (average birth weight less than 3rd centile, mortality rate 50%, significantly lower umbilical artery blood pH and Apgar scores after 1 and 5 min). Intrauterine fetal death occurred in five fetuses after a median of 3.5 days following visualization of coronary blood flow. Median coronary peak blood flow velocities in the right coronary artery were higher in intrauterine growth-retarded than appropriate-for-gestational-age fetuses.

Fetal atrioventricular flow-velocity waveforms and their relation to arterial and venous flow-velocity waveforms at 8 to 20 weeks of gestation.

Doppler ultrasonography was used to determine the nature and gestational age-related changes of human fetal AV flow-velocity waveforms and to establish their relationship with arterial impedance indexes and venous flow velocities in normal human fetuses between 8 and 20 weeks of gestation. Flow-velocity waveform recordings were attempted in 318 singleton pregnancies. After the exclusion criteria were applied, data on 214 women were available for further analysis. Differentiation between E wave and A wave became possible at 9 weeks, whereas distinction between transmittal and transtricuspid valve flow velocities was first achieved at 10 to 11 weeks. A statistically significant nonlinear gestational age-dependent increase was established for all AV waveform parameters, which became linear when related to logarithmically estimated fetal crown-to-rump length. Transtricuspid valve flow velocities were significantly higher than transmittal valve flow velocities. Transmittal valve time-averaged flow velocities were positively correlated with peak diastolic velocities and time-velocity integral of late-diastolic reverse flow in the inferior vena cava. No correlation existed between AV time-averaged velocities and arterial impedance indexes. Monophasic AV flow-velocity waveforms can be recorded as early as 8 weeks of gestation and become biphasic as early as 8 weeks. They demonstrate a linear increase relative to logarithmically estimated fetal crown-to-rump length, suggesting that fetal growth-related increase in volume flow plays a role in this velocity rise. Transtricuspid valve A-wave and E-wave velocities suggest right ventricular predominance as early as the late first trimester of pregnancy. AV flow velocities are not related to arterial downstream impedance.

Doppler assessment of the fetal circulation in early and late fetal development

With the advent of Doppler ultrasound, fetal cardiac performance has been studied in isolation and in relation to the fetal circulation in general both under physiological and pathophysiological circumstances. In this chapter the central theme is the changes in arterial downstream impedance which occur relative to normal and abnormal fetal development and their association with cardiac and venous flow velocity waveforms. Changes in arterial downstream impedance as expressed by descending aorta and umbilical artery pulsatility index are observed in: (i) normal embryonic/early fetal development; (ii) normal late fetal development associated with behavioural states, and (iii) abnormal late fetal development, in particular fetal growth retardation.

Abnormal fetal pulmonary venous blood flow velocity waveforms in the presence of complete transposition of the great arteries

Abnormal fetal pulmonary venous blood flow velocity waveforms in the presence of complete transposition of the great arteries

Umbilical cord venous pulsation in normal fetuses and its incidence after 13 weeks of gestation

A total of 1175 umbilical venous Doppler flow velocity waveforms were acquired from 449 normal pregnant women whose fetuses were delivered at term without neonatal asphyxia or anomalies. Arterial and venous flow velocity waveforms were acquired from a free loop of the umbilical cord. The incidence of umbilical venous pulsation decreased from 30.4% at 13 ∼ 14 weeks of gestation to 14.8% at 21–22 weeks of gestation. After 23 weeks, this incidence was settled within 5.0∼7.8%. There was no difference between the umbilical arterial resistance index of the fetuses with venous pulsation and without pulsation before 22 weeks. But the resistance index was lower in the pulsatile fetuses than in the nonpulsatile fetuses after 23 weeks of gestation. The origin of venous pulsations before early second trimester was suspected to be different from that after late second trimester.