Altered fetal circulation in type-1 diabetic pregnancies.

OBJECTIVE: Type-I diabetic pregnancies are associated with congenital cardiac malformations, fetal cardiomyopathy, venous thrombosis and altered placental vascularization, even with tight maternal glucose control. The aim of this study was to investigate if, with good glucose control achieved with continuous subcutaneous insulin infusion, normal blood flow within the fetal heart can be achieved. METHODS: Seventeen fetuses of women with well-controlled type-I diabetes were studied longitudinally to evaluate effects on the fetal circulation. Doppler frequency shift tracings, valve diameters and intercept angles were measured at right and left atrioventricular valve orifices at 4-week intervals starting at 15 weeks' gestation. Atrioventricular valve flow was calculated and compared to normal fetal data obtained in previous studies. RESULTS: Maximum and mean temporal velocities across the atrioventricular valves increased in both groups during gestation but significantly more in fetuses of type-I diabetic pregnancies. Combined ventricular output, both absolute and per kg estimated fetal weight, were also greater in these fetuses. In the normal group the ratio of the right/left ventricular output decreased significantly during gestation (from 1.34 +/- 0.28 to 1.08 +/- 0.28 standard deviations), but in type-I diabetic pregnancies this decrease did not occur (1.2 +/- 0.26 to 1.25 +/- 0.29 standard deviations)[corrected]. CONCLUSIONS: These data indicate that there are significant differences in the fetal circulation between normal pregnancy and well-controlled type-I diabetic pregnancy, suggesting the existence of a compensatory mechanism which increases fetal cardiac output and causes cardiac hypertrophy.     

Coronary artery blood flow velocities in various fetal conditions.

OBJECTIVE: To determine fetal coronary artery peak blood flow velocities in normal and high-risk pregnancies. METHODS: Coronary artery peak systolic and diastolic blood flow velocities were measured by pulsed-wave Doppler velocimetry after identification of the coronary arteries by color Doppler imaging. Peak blood velocities obtained from normal pregnancies were related to gestational age using linear regression analysis. Blood flow velocities in normal fetuses were compared to measurements obtained in various fetal conditions. RESULTS: In normal fetuses coronary artery blood flow was visualized at a median gestational age of 33 + 6 weeks; median systolic and diastolic peak blood flow velocities were 0.21 and 0.43 m/s, respectively, and showed no significant change with gestational age. In growth-restricted fetuses coronary artery blood flow was visualized significantly earlier in gestation (median 28 + 2 weeks); systolic and diastolic peak blood flow velocities were higher at 0.25 and 0.48 m/s, respectively (P < 0.05). The highest coronary blood flow velocities were observed with fetal anemia. Coronary artery blood flow was also measured in fetuses with ductus arteriosus constriction due to indomethacin. Velocities did not differ from normal fetuses. Both in fetal anemia and ductus arteriosus constriction coronary artery blood flow could no longer be visualized with resolution of the underlying condition. CONCLUSION: Examination of coronary artery blood flow dynamics in the human fetus demonstrates acute increases in diastolic velocities in severe anemia and ductus arteriosus constriction based on the severity of the condition. In fetuses with growth restriction increased coronary blood flow velocities can be appreciated throughout the cardiac cycle. Clinical correlation in the interpretation of coronary blood flow dynamics in the human fetus is essential.     

Color Doppler study of the venous circulation in the fetal brain and hemodynamic study of the cerebral transverse sinus.

OBJECTIVES: To describe the venous circulation in the fetal brain; to describe the normal blood flow velocity waveform in the transverse sinus and to establish normal reference ranges for the second half of gestation. POPULATION: A total of 126 pregnant women with uncomplicated pregnancies at 20-42 weeks of gestation. METHODS: A combination of color-coded Doppler and two-dimensional real-time ultrasound was used to identify the main venous systems in the fetal brain. Blood flow velocity waveforms of the transverse sinus were obtained from a transverse plane of the head at the level of the cerebellum. RESULTS: A waveform could be obtained in the cerebral transverse sinus in 98% of the cases. The waveform obtained was triphasic with a forward systolic component, a forward early diastolic component and a lower forward component in late diastole. Reverse flow during atrial contraction was seen before 28 weeks and the diastolic flow increased with gestation thereafter. Pulsatility and resistance indices decreased and flow velocities increased in the transverse sinus throughout gestation. CONCLUSION: The venous circulation of the fetal brain can be identified by color Doppler. The gestational age-related decrease in resistance and increase in flow velocities suggest that hemodynamic studies of the cerebral transverse sinus might have clinical implications in studying compromised fetuses.     

Human fetal foramen ovale flow velocity waveforms relative to fetal breathing movements in normal term pregnancies.

The relationship between foramen ovale flow velocity waveforms and high-amplitude fetal breathing movements was studied in ten normal term pregnancies using Doppler ultrasonography. Peak systolic and averaged flow velocities demonstrated a statistically significant increase during fetal breathing activity, suggesting a raised pressure gradient between the right and left atria. This could be explained by a temporal reduction in pulmonary venous return to the left atrium during the inspiratory phase of the fetal breathing cycle. The breathing-related increase in foramen ovale flow velocity suggests that fetal breathing activity facilitates the distribution of well-oxygenated blood to the aorta and cerebral circulation.     

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

OBJECTIVES: To evaluate the potential usefulness of noninvasive ultrasound assessment of fetal anemia in the diagnosis and management of fetuses with homozygous alpha-thalassemia-1. METHODS: 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. RESULTS: 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. CONCLUSION: 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.     

Fetal cardiac arrhythmias and their effect on volume blood flow in descending aorta of human fetus

Using a two-dimensional linear array real-time and pulsed Doppler ultrasound system, volume blood flow measurements were made in 86 normal pregnancies, seven cases of fetal bradycardia, and seven cases of fetal tachycardia at the lower thoracic level of the fetal descending aorta. During fetal cardiac arrhythmias, volume blood flow was maintained within the normal range until the heart rates reached around 50 bpm and 230 bpm, after which the volume blood flow diminished. The changes observed suggest that the Frank-Starling mechanism is functional in the fetal myocardium and demonstrate the stability of the fetal circulation.     

Transvaginal color Doppler study of middle cerebral artery blood flow in early normal and abnormal pregnancy.

Transvaginal color and pulsed Doppler sonography was performed on 106 singleton pregnant women; 75 had clinically normal pregnancies, and the remaining 31 patients had complicated pregnancies with vaginal bleeding. The gestational ages ranged from the 7th to 18th menstrual weeks. The aim of the study was to establish the earliest gestational age at which intracranial blood flow could be detected, in particular in the middle cerebral artery. The intracranial circulation becomes visible at the 8th week of gestation (7 weeks and 3 days). The end-diastolic component of blood flow is inconstantly present from the 11th to the 13th gestational week, and is always detected thereafter. A significant decrease in the pulsatility index (p < 0.05) and peripheral flow impedance index (p < 0.001) was observed during the early weeks of pregnancy in both the normal and complicated pregnancies. There was no significant difference between the groups (p > 0.05). Results suggest that Doppler studies of middle cerebral arteries in early pregnancy are unlikely to be of value in identifying fetal hemodynamic disorders in the early stages of spontaneous abortion.     

Fetal and placental power Doppler imaging in normal and high-risk pregnancy.

OBJECTIVE: Computer analysis of organ power Doppler (PD) imaging has recently become available. The aim of the study was to evaluate gestational trends in placenta-, fetal lung-, liver- and kidney-blood flow in normal pregnancies and relate it to signals in high-risk pregnancies. METHODS: PD signals were recorded in normal singleton pregnancies between 26 and 42 weeks of gestation. Signals were also recorded in 63 high-risk pregnancies. Fixed preinstalled PD system installations for each organ were used during examinations. Images from PD scan were recorded on video tape and off-line analysed by computer. Mean flow signal intensity was calculated for each organ. Umbilical and uterine artery Doppler velocimetry were also recorded in high-risk pregnancies. RESULTS: PD signals from the four organs indicated increasing organ blood flow until approximately 34 weeks of gestation, from where the organ signals seemed to decrease. High-risk pregnancies seemed to have lower PD signal intensity, which was more pronounced in cases with signs of placental vascular resistance. CONCLUSION: The results suggest that a decrease in fetal organ blood flow might indicate a centralisation of fetal circulation in normal pregnancy at term, as a physiological response to a decrease in placental perfusion. In the high-risk pregnancies the placental and fetal organ blood flow seem to be even further reduced, suggesting a more intense centralisation of circulation.     

The pulmonary vein Doppler flow velocity waveform: feature analysis by comparison of in vivo pressures and flows with those in a computerized fetal physiological model.

OBJECTIVES: Doppler flow velocity waveforms (FVW) in fetal veins that discharge into the atria show fluctuations related to atrial events. Pulmonary veins are of particular interest because both ends (atrial and collecting venule) are within the intrathoracic pressure environment reducing fetal breathing artifacts. Indices, such as pulsatility index for veins (PIV), have been suggested to classify FVWs and relate them to fetal well being. We wished to examine the relationship between function and FVW in circumstances which cannot ethically be examined in vivo, by studying the mechanisms which produced altered 'flows' in a detailed fetal computer model. We then related these findings to current flow indices. METHODS: A computer model of the feto-placental unit, responding to changes in organ oxygenation and regional flow is briefly described. In vivo intracardiac pressures and FVWs obtained from other studies were used to extend detail in the model until matching 'pressures' and 'flows' resulted. The effects of flow redistribution in the hypoxic fetus on pulmonary vein 'Doppler' flow velocity waveforms were then studied. RESULTS AND CONCLUSIONS: Flow reversal in pulmonary veins during atrial contraction indicates hypoxia, but change of shape of the FVW envelope reflects the changes in the pressure waveform of the left atrium. Of the major veins the pulmonary vein Doppler FVW gave the truest representation of atrial pressure response to both intracardiac and systemic vascular status. Although current indices indicate general fetal condition, more specific indices are needed if pulmonary venous flow is to be used as an end-point. A pulmonary vein pressure gradient index is suggested.     

大脑中动脉血流参数比值在胎儿高动力循环状态中的初步应用

目的 探讨预测胎儿高动力循环状态的血流参数比值指标。方法 应用二维超声、彩色多普勒能量图及脉冲多普勒技术对17例17－31孕周高动力循环状态胎儿及215例16－31孕周正常胎儿大脑中动脉血流参数及头围进行检查。结果 高动力循环状态组胎儿每分钟单位头围大脑中动脉的最大速度及平均速度均高于正常组（P＜0．05）。结论 大脑中动脉血流参数比值能预测胎儿高动力循环状态。     

2,3-Diphosphoglycerate in normal, anaemic and transfused human fetuses

1. The effect of anaemia and transfusion with adult blood on fetal 2,3-diphosphoglycerate levels was investigated by studying fetal blood from 45 normal pregnancies at 17-42 weeks of gestation and in 34 pregnancies complicated by erythroblastosis fetalis. 2. In normal fetuses, 2,3-diphosphoglycerate concentration was higher than in adults and did not change significantly with gestational age. 3. In erythroblastotic fetuses, there was a significant negative correlation between 2,3-diphosphoglycerate concentration and haemoglobin concentration. 4. When adult blood was transfused into the fetal circulation, 2,3-diphosphoglycerate concentration reached similar levels to that found in untransfused fetuses after allowing for the severity of anaemia.     

正常中孕胎儿大脑中动脉血流参数比值的正常值范围

目的 确定正常中孕胎儿大脑中动脉血流参比值的正常值范围。方法 应用二维超声、彩色多普勒能量图及脉冲多普勒技术对215例16-31孕周正常胎儿头围、体重及大脑中动脉血流参数进行检测。结果 正常中孕胎儿每分钟单位体重大脑中动脉的最大速度及平均速度随孕周的增加而降低;每分单位头围大脑中动脉的最大速度及平均速度在中孕期间变化小。结论 本研究为多普勒超声早期预测胎儿高动力循环状态提供了理论依据。     

Circulatory effects of acute bradycardia in the human fetus as studied by Doppler ultrasound.

OBJECTIVE: To report on flow changes in fetal arterial, venous and coronary vessels during bradycardia following cordocentesis. Changes in the fetal circulation in response to acute challenges are incompletely understood. METHODS: Fetal blood sampling was performed at 29 + 4 weeks for chromosome analysis in a fetus with multiple malformations including a complete atrioventricular septal defect with competent atrioventricular valve. The procedure was complicated by a 12-min bradycardia of 57 beats/min. 'Heart sparing' (sudden visualization of coronary blood flow) and 'brain sparing' (increased diastolic velocities in the middle cerebral artery) were demonstrated by Doppler examination despite marked circulatory compromise (regurgitation of atrioventricular valve, increased reverse flow in precordial veins and pulsatile umbilical vein flow pattern) which persisted after normalization of the fetal heart rate. The findings had resolved completely at a full cardiovascular examination 6 h after the bradycardia. Pregnancy termination was subsequently performed for partial monosomy 13q. CONCLUSION: Protective fetal changes producing 'heart sparing' and 'brain sparing' and may be operational during episodes of acute fetal bradycardia.     

Reverse flow in the human fetal descending aorta as a sign of severe fetal asphyxia preceding intrauterine death

Flow velocity waveforms (FVW) in the descending part of the human fetal aorta were monitored in 35 cases of severe intrauterine growth retardation (IUGR) showing pathological intrauterine circulation (end-diastolic block). In 5 of the 35 fetuses, reversed aortic flow was observable during diastole and the simultaneously recorded CTG findings were pathological. All 5 fetuses having this circulatory sign died in utero within the next day. Controls were 260 healthy fetuses with normal growth curves; no end-diastolic block or reverse flow was found in this group. Diastolic reverse flow in the fetal descending aorta appears to reflect severely altered circulation preceding imminent fetal death.     

Reference ranges for serial measurements of blood velocity and pulsatility index at the intra-abdominal portion, and fetal and placental ends of the umbilical artery.

OBJECTIVE: To construct reference ranges for serial measurements of umbilical artery (UA) blood flow velocity and pulsatility index (PI) at standardized insonation sites during the second half of pregnancy. METHODS: This was a prospective longitudinal study of the umbilical circulation. UA blood flow velocities were measured at the intra-abdominal portion, fetal end and placental end at 4-weekly intervals at 19-42 weeks of gestation in 130 low-risk singleton pregnancies. A total of 513 observations were used to construct the reference ranges using regression statistics and multilevel modeling. RESULTS: UA blood velocities and PI were higher at the intra-abdominal portion and fetal end than at the placental end. The gestational age-related increase of end-diastolic velocity was greater than the corresponding increase of the peak systolic velocity at all locations. The mean differences (delta values) of UA blood velocities between the fetal and placental ends increased and that of PI decreased with advancing gestational age. CONCLUSION: UA Doppler parameters vary significantly at different locations. We have established new reference ranges for the UA velocities and PI at standardized locations based on longitudinal observations, which should be useful for the surveillance of fetuses with repeated observations.     

Fetal heart rate and umbilical artery velocity variability in pregnancies complicated by insulin-dependent diabetes mellitus.

OBJECTIVES: To examine the variability in fetal heart rate and absolute flow velocity, which are possible hemodynamic markers of cardiovascular homeostasis in pregnancies complicated by diabetes mellitus. METHODS: Doppler studies of umbilical artery velocity waveforms were performed at 12-21 weeks of gestation in 16 women with well-controlled type I (insulin-dependent) diabetes mellitus. From umbilical artery velocity waveforms of at least 13 s in duration, we determined absolute values and beat-to-beat variability for fetal heart rate and umbilical artery flow velocities and compared these findings with normal controls matched for gestational age. RESULTS: Fetuses of diabetic women displayed increased fetal heart rate variability and umbilical artery peak systolic velocity. Fetal heart rate, umbilical artery time-averaged velocity and variability in umbilical artery flow velocity were not essentially different between the two groups. CONCLUSION: Fetal heart rate variability and umbilical artery peak systolic velocity may be markers for fetal cardiovascular homeostasis in pregnancies complicated by insulin-dependent diabetes mellitus.     

The Importance of Venous Doppler Velocimetry for Evaluation of Intrauterine Growth Restriction

The management of growth‐restricted fetuses requires accurate diagnosis to optimize the timing of delivery. Doppler velocimetry is the only noninvasive method for assessing the fetoplacental hemodynamic status. This review will give a critical overview of the current knowledge on fetal venous blood flow in pregnancies complicated by in‐trauterine growth‐restricted fetuses. Adaptation of the circulation in intrauterine growth‐restricted fetuses is described. Normal and abnormal venous Doppler waveforms are presented. Correlations of abnormal waveforms with the presence of acidemia and perinatal outcomes are emphasized. Limitations of venous Doppler velocimetry for optimizing the time for delivery and the perinatal outcome are also presented.     

Uterine artery blood flow velocity waveforms during uterine contractions.

OBJECTIVE: No quantitative or qualitative Doppler velocimetry classification of vascular flow resistance covering all stages of forward and reversed flows exists. The objective of this study was to characterize uterine artery (UtA) flow velocity waveforms (FVWs) obtained during an oxytocin challenge test (OCT) and compare them to FVWs in spontaneous normal labor. METHODS: Uterine artery Doppler velocimetry was performed during and between uterine contractions in 61 high-risk pregnancies subjected to an OCT and in 20 normal pregnancies undergoing spontaneous labor. FVWs were classified relative to the presence of forward/absent/reversed flow during systole and diastole, and the time-averaged flow velocity over the heart cycle. RESULTS: Eleven different FVW classes were identified. No relationship between FVWs recorded during uterine inertia and contractions was found (P >/= 0.2). In both groups, only forward FVWs were recorded between contractions, whereas during contractions flow reversal was more common in the OCT group (P 相似文献   

Recording of blood flow velocity waveforms in the uteroplacental and umbilical circulation: reproducibility study and comparison of pulsed and continuous wave Doppler ultrasonography

Reproducibility of the blood flow velocity waveforms (FVW) recorded from the umbilical artery and the arcuate arteries on the right and left side of the placenta was examined in 8 women with normal pregnancies and anterior placentas. The FVW were recorded using a 2-MHz pulsed Doppler ultrasound system in combination with a real-time linear-array scanner. The FVW were characterized by the pulsatility index (PI) and systolic/diastolic (S/D) ratio. For the PI, the mean coefficients of variation between six operator pairs in the umbilical artery and the left and right arcuate arteries were 8.4%, 26%, and 21.5%, respectively. These findings suggest that, in clinical practice, the umbilical artery FVW is reproducible, but the usefulness of arcuate artery FVW is limited by the wide variation of Doppler signals. Paired recordings of FVW were obtained from the umbilical, arcuate, and uterine arteries using pulsed wave and continuous wave Doppler ultrasonography in a randomized order in another 21 pregnant women with anterior placentas. There was no difference between the two Doppler modes for any of the measured waveform indices.     

晚期妊娠合并羊水过少胎儿肾动脉血流的观察

目的　了解晚期妊娠合并羊水过少胎儿肾动脉血流的特点及其预测胎儿宫内缺氧的价值。方法　应用彩色多普勒超声分别检测 15例妊娠晚期合并羊水过少和 3 2例正常晚期妊娠胎儿的肾动脉搏动指数。结果　与正常组比较 ,妊娠晚期合并羊水过少的胎儿肾动脉搏动指数明显升高。结论　胎儿肾动脉异常的搏动指数与羊水过少两者合并情况下 ,可预测胎儿的宫内缺氧