超声测量胎儿主动脉峡部血流多普勒指标的意义

胎儿宫内缺氧严重威胁胎儿宫内安危,长期以来受到产科医师的关注。早期发现、及时处理和治疗,对降低围生儿死亡率、提高围生医学质量具有重大意义。目前临床上应用彩色多普勒超声测量胎儿的脐动脉、大脑中动脉等各种血流指标,以评估胎儿宫内缺氧的情况。现从简单、方便、快捷、有效等各方面,探讨超声测量胎儿主动脉峡部血流多普勒指标对早期发现胎儿宫内缺氧的意义。     

胎儿宫内窘迫时的胎儿胎盘血液动力学改变

目的：评价彩色多普勒超声检查在围产儿监护方面的价值。方法：对２２例胎儿宫内缺氧（宫内窘迫组）和６例围产儿死亡（围产儿死亡组）的胎儿胎盘血管超声结果进行分析，同时与同期５５５例妊娠３６～４０周正常妊娠胎儿（正常妊娠组）比较。使用仪器为ＵＭ９ＨＤＩ彩色多普勒超声诊断仪。结果：与正常妊娠组比较，胎儿宫内窘迫组胎儿肾动脉、脐动脉和胎盘床动脉阻力均显著升高，大脑中动脉阻力无变化；围产儿死亡组中，除胎儿外周血管阻力升高外，其大脑中动脉阻力明显降低，以及脐动脉和肾动脉舒张期血流缺如或返流。结论：胎儿宫内缺氧使胎儿血液动力学发生明显的变化，血液动力学变化，对预测胎儿宫内缺氧具有一定的价值。     

彩色多普勒超声在预测死胎中的作用

死胎是指妊娠大于23+6周、无生命迹象的胎儿,是围产儿死亡的主要原因之一,产前有效预测死胎,对降低围产儿死亡率具有重大意义。利用彩色多普勒超声监测不同孕期母体子宫动脉血流参数,特别是妊娠中期子宫动脉搏动指数(PI)对与子痫前期、胎盘早剥、小于胎龄儿(SGA)相关的死胎预测有重要意义;监测胎儿各项多普勒血流参数,如脐动脉、大脑中动脉、静脉导管、腹内脐静脉等,能够反映胎儿宫内缺氧状况,提高胎儿窘迫的诊断率;联合监测母体及胎儿各项血流参数,全面评估胎儿宫内缺氧程度并及时干预,可避免死胎的发生。     

用彩色超声仪与多功能多普勒仪监测胎儿脐血流S/D值的比较

胎儿脐动脉血流速度波形是反映胎儿－胎盘循环状态的指标之一,当胎儿脐动脉血流出现阻断或逆流的异常波形时,反映胎儿－胎盘循环血流量严重不足;血流阻力指标极度升高表明胎儿宫内缺血、缺氧严重,在胎儿脐动脉逆流波形出现时有４０％～５０％的围产儿死亡,及时终止妊...     

超声检查诊断胎儿贫血的研究进展

产前预测胎儿宫内贫血,对指导临床干预、降低围生儿死亡率,提高围生医学质量具有重要意义。传统的产前诊断胎儿溶血性贫血的方法属于有创性检测,增加了妊娠妇女与胎儿的风险。近年来采用二维、三维及彩色多普勒超声产前诊断胎儿贫血取得了较大的进展,研究较多的指标包括胎盘厚度及体积;胎儿大脑中动脉血流峰速(MCA-PSV);胎儿心血管循环;脾动脉峰值流速;游离段脐动脉、脐静脉的内径,脐动脉搏动指数,以及肝内段脐静脉收缩期峰值血流速度;静脉导管峰值流速等。在众多超声指标中,MCA-PSV是敏感度及特异度最高的指标,联合多个指标将提高诊断的准确性。     

彩色多普勒超声检查胎儿脐动脉血流预测胎儿宫内状况及预后

本文应用 Acusonl 128彩色电脑超声仪检查了180例16～40孕周孕妇的胎儿脐动脉缸流,分了血流指标 PI 和 A/Bratio(脐动脉收缩期血流速度峰值与舒张期血流速度峰值之比)的数值.结果表明,多普勒(Doppler)脐动脉血流频谱的改变能比胎儿心率改变更早地反映胎儿宫内缺氧,血流频谱的异常程度与胎儿宫内缺氧的程度相一致,脐动脉舒张期血流停滞或倒流示胎儿处于重度缺氧和中毒状态.极易发生围产儿死亡.血流频谱异常还可预测胎儿的预后.本文提示:Doppler 脐动脉血流检查是一项有极高临床价值的新方法,值得推广使用.     

脐血流和胎心监护与胎儿宫内缺氧及围产儿预后的关系

胎儿脐动脉血流速度监测和胎心监护两种方法结合应用能更准确地判断胎儿宫内缺氧，经积极治疗有利于改善围产儿的预后。     

超声多普勒测定脑-胎盘比在产科的应用

脑-胎盘比（cerebroplacental ratio，CPR）为胎儿大脑中动脉搏动指数（pulsatility index，PI）和脐动脉PI的比值，其是反映胎儿宫内缺氧的一项敏感指标，近年来逐渐引起产科和超声科医师的关注。文章依据目前国内外临床研究，阐述CPR在评估胎儿生长发育状况及预测不良围产结局方面的价值。     

妊娠晚期胎儿缺氧的预测及治疗探讨

我们利用彩色多普勒超声仪 (ｃｏｌｏｕｒｄｏｐｐｌｅｒｆｌｏｗｉｍａｇｉｎｇ,ＣＤＦＩ)检测胎儿脐动脉 (ｕｍｂｉｌｉｃａｌａｒｔｅｒｙ ,ＵｍＡ)、大脑中动脉(ｍｉｄｄｌｅｃｅｒｅｂｒａｌａｒｔｅｒｙ ,ＭＣＡ)的血流速度 ;利用胎心监护仪检测胎心率 ,综合分析胎儿缺氧程度 ,根据缺氧程度采取不同的治疗方法 ,以进一步评价用ＣＤＦＩ检测胎儿ＵｍＡ、ＭＣＡ与胎心监护仪诊断孕晚期胎儿宫内缺氧并及时经母体给药纠正胎儿宫内缺氧的临床价值。1　资料与方法1.1　临床资料　 1997年 10月至 1999年 10月 ,在我院产前检查及住院的孕妇 90…     

胎儿缺氧的妊娠期监测

目前临床用于监测胎儿宫内安危的手段主要包括胎动计数、胎儿电子监护、生物物理评分、胎儿脑电图和多普勒超声等。胎动计数简单但主观性强,胎儿电子监护假阳性率高,生物物理评分操作费时,胎儿脑电图临床使用相对受限,而多普勒超声对于血流的监测如孕妇子宫动脉、胎儿脐动脉、脐静脉、大脑中动脉、腹主动脉、肾动脉、静脉导管等对孕期监测胎儿宫内安危较为简单方便,而目前应用最多的仍是胎儿脐动脉血流的监测。     

胎儿大脑中动脉血流在高危妊娠中应用价值的研究进展

胎儿大脑中动脉（MCA）是胎儿大脑血流供应最丰富的血管,对反映胎儿脑部血液循环改变及血氧情况的变化有重要的临床应用价值。正常妊娠时,随着孕周增加,胎儿脑部发育逐渐完善,胎儿MCA彩色多普勒超声血流信号指标的变化呈抛物线模式。在高危妊娠中,胎盘功能不足、血管阻力增加与不良妊娠结局之间呈一定的相关性。MCA具有自身调节功能,当胎儿的内外环境出现变化时如缺氧等可导致MCA的血流动力学发生改变,而胎儿MCA彩色多普勒超声的各项血流信号指标也呈异常的变化趋势。彩色多普勒超声检查胎儿MCA血流动力学指标对母儿双方安全、无创、方便以及可重复性高,可用来反映胎儿的一系列病理生理改变,成为近年来临床评估胎儿生长发育和宫内安危状况的重要监测手段。。     

Can anomalies of fetal brain circulation be useful in the management of growth restricted fetuses?

Assessment of the fetal cerebral circulation provides important information on the hemodynamic changes associated with chronic hypoxia and intrauterine growth restriction. Despite the incorporation of new US parameters, the landmark for the fetal brain hemodynamic evaluation is still the middle cerebral artery. However, new vascular territories, such as the anterior and posterior cerebral arteries, might provide additional information on the onset of the brain sparing effect. The fractional moving blood volume estimation and three-dimensional power Doppler ultrasound indices are new techniques that seem to be promising in identifying cases at earlier stages of vascular deterioration; still, they are not available for clinical application and more information is needed on the reproducibility and advantages of three-dimensional power Doppler ultrasound blood flow indices. In the past, the brain sparing effect was considered as a protective mechanism; however, recent information challenges this concept. There is growing evidence of an association between brain sparing effect and increased risk of abnormal neurodevelopment after birth. Even in mild late-onset intrauterine growth restriction affected fetuses with normal umbilical artery blood flow, increased cerebral blood perfusion can be associated with a substantial risk of abnormal neuroadaptation and neurodevelopment during childhood.     

Doppler assessment of the fetal asphyxia in pregnancies complicated by gestational hypertension and intrauterine growth retardation

OBJECTIVES: Gestational hypertension is associated with a high morbidity for both mother and fetus. Doppler ultrasound has allowed the fetal circulation to be examined. Now it is possible to monitor the response of the fetal circulation to hypoxia. DESIGN: The aim of this study was to determine flow patterns in fetal circulation from pregnancies complicated by gestational hypertension and intrauterine growth restriction. MATERIALS AND METHODS: The investigation included 23 fetuses with signs of the gestational hypertension and intrauterine growth restriction. We evaluated cerebral-placental ratio (CPR) and pulsation index (PI) in the middle cerebral artery (MCA) and the umbilical artery (UA). We also evaluated flows in umbilical vein. RESULTS: We observed abnormal flow pattern in all cases of analyzing fetuses. The most common abnormal flow was vein pulsation (48%). CONCLUSIONS: All analyzing fetuses shown signs of the hypoxia. Present of the umbilical vein pulsation or decompensate of the brain sparing effect is closely related o increased perinatal mortality.     

Doppler ultrasound in obstetrics

Doppler ultrasound is used to assess and monitor high-risk pregnancies and time delivery appropriately. Pregnancies with high resistance in the uterine arteries (UtA) are at risk of pre-eclampsia and fetal growth restriction (FGR) and need close monitoring. Umbilical artery Doppler reflects blood flow within the placenta and increased resistance within the umbilical arteries (UmA) reflects placental dysfunction. In situations with abnormal UmA blood flows, further assessment of fetal Dopplers such as middle cerebral artery (MCA) and ductus venosus (DV) enables timely delivery by identifying progressive changes in fetal circulation with progressive hypoxia. A fetus with chronic hypoxia will demonstrate cerebrovascular dilation and reduced resistance in the middle cerebral arteries. The DV Doppler reflects cardiac function and becomes abnormal with increasing hypoxia and acidosis. Increased survelliance with additional fetal Doppler blood flows such as DV Dopplers allows to prolong these pregnancies and reduces risks from extreme preterm delivery.     

Adrenomedullin is increased in the fetoplacental circulation in intrauterine growth restriction with abnormal umbilical artery waveforms

OBJECTIVE: To examine whether adrenomedullin, a novel vasoactive peptide produced by the placenta, participates in the uteroplacental hemodynamic alterations in intrauterine growth restriction, we studied the correlation between adrenomedullin levels and fetoplacental blood flow. STUDY DESIGN: Maternal and umbilical blood samples were collected in pregnancies complicated by intrauterine growth restriction with abnormal umbilical artery Doppler findings and in control pregnancies. Adrenomedullin levels were measured by means of a specific radioimmunoassay, and flow velocimetry waveforms were recorded from uterine, umbilical, and fetal middle cerebral arteries. RESULTS: Mean adrenomedullin values in umbilical plasma were higher (P <.05) in patients with intrauterine growth restriction (63.7 +/- 34.2 pg/mL; n = 16) than in control subjects (38.1 +/- 14.8 pg/mL; n = 16). A significant correlation was found between maternal adrenomedullin levels and umbilical artery pulsatility index. Moreover, fetal adrenomedullin concentrations correlated negatively with middle cerebral artery pulsatility index and positively with umbilical artery pulsatility index/middle cerebral artery pulsatility index ratio. CONCLUSION: This study provides evidence that adrenomedullin is increased in fetuses with intrauterine growth restriction in response to reduced uteroplacental blood flow and suggests that it may participate in the fetal hemodynamic modifications.     

Assessment of blood flow in the middle cerebral artery and the umbilical artery in fetuses with umbilical venous pulsations

OBJECTIVES: Umbilical venous pulsation is an important sign of hemodynamic compromise, especially during fetal heart failure and asphyxia. DESIGN: The aim of this study was to determine of the blow flow in the middle cerebral artery and the umbilical artery in fetuses with umbilical venous pulsations. MATERIALS AND METHODS: The investigation included 18 fetuses with signs of the intrauterine growth restriction and umbilical venous pulsations after 28th weeks of gestation. We evaluated cerebral-placental ratio (CPR) and pulsation index (PI) in the middle cerebral artery (MCA) and the umbilical artery (UA). RESULTS: We observed brain sparring effect in all cases of analyzing fetuses. There were 77,8% of abnormal flow pattern in umbilical artery. 13 fetuses had a single pulsation pattern in umbilical vein and another 5 had double pulsation pattern. CONCLUSIONS: The coexistence of umbilical vein pulsation and abnormal flow pattern in umbilical artery is closely related to increased perinatal mortality.     

Assessment of motoric and hemodynamic parameters in growth restricted fetuses – case study

Abstract

Objective: In order to more accurately assess fetal neurological status in five fetuses with severe intrauterine growth restriction (IUGR), combined assessment of their hemodynamics and motor activity was undertaken in this study.

Method: Hemodynamic changes in the placental and fetal cerebral vessels were evaluated using the umbilical artery resistance index (URI), and the middle cerebral artery resistance index (CRI). The blood flow redistribution towards the fetal brain in response to fetal hypoxia was detected by the C/U (cerebro – umbilical) ratio, expressed as CRI/URI.

Motoric parameters were assessed by new antenatal neurologic scoring test named Kurjak Antenatal Neurodevelopmental Test (KANET), based on evaluation of spontaneous motor activity using four-dimensional (4D) ultrasound.

Results: KANET has potential in recognizing pathologic and borderline behavior in IUGR fetuses with or without blood flow redistribution towards the fetal brain. Very low values of C/U ratio and abnormal KANET score have indicated adverse pregnancy outcome.

Conclusion: In some pregnancies complicated with IUGR, estimation of the risk of hypoxia versus prematurity can be extremely puzzling. Combined assessment of hemodynamic and motoric parameters in IUGR fetuses could allow construction of an algorithm, which would be helpful in the decision making process of pregnancy termination.     

Fetal cerebrovascular response to chronic hypoxia--implications for the prevention of brain damage.

Fetal hypoxia is one of the leading causes of perinatal morbidity and mortality. One of the most severe sequels of fetal hypoxic insult is the development of perinatal brain lesions resulting in a spectrum of neurological disabilities, from minor cerebral disorders to cerebral palsy. One of the most important fetal adaptive responses to hypoxia is redistribution of blood flow towards the fetal brain, known as the 'brain sparing effect'. The fetal blood flow redistribution in favor of the fetal brain can be detected and quantified by the Doppler cerebral/umbilical ratio (C/U ratio = cerebral resistance index (CRI)/umbilical resistance index (URI)). Our studies on animal models and human fetuses have demonstrated clearly that this phenomenon cannot prevent the development of perinatal brain lesions in the case of severe or prolonged hypoxia. Fetal deterioration in chronic and severe hypoxia is characterized by the disappearance of the physiological cerebral vascular variability (vasoconstriction and vasodilatation), followed by an increase in cerebral vascular resistance. However, our latest study on growth-restricted and hypoxic human fetuses has shown that perinatal brain lesions can develop even before the loss of cerebrovascular variability. The fetal exposure to hypoxia can be quantified by using a new vascular score, the hypoxia index. This parameter, which takes into account the degree as well as duration of fetal hypoxia, can be calculated by summing the daily % C/U ratio reduction from the cut-off value 1 over the period of observation. According to our results, the use of this parameter, which calculates the cumulative, relative oxygen deficit, could allow for the first time the sensitive and reliable prediction and even prevention of adverse neurological outcome in pregnancies complicated by fetal hypoxia.     

Hemodynamic changes in the fetal arteries during the second half of pregnancy assessed by Doppler velocimetry

The applicability of Doppler velocimetry has been well established regarding intrauterine growth restriction and fetal hypoxia. This method can also be used to determine fetal anemia and cardiac malformations. The main fetal arteries evaluated by Doppler velocimetry are the middle cerebral artery and the umbilical artery. However, the fetal aorta is responsible for the distribution of blood flow to the upper and lower extremities of the human body and should also be properly valued. In order to characterize abnormalities in the arteries of high-risk fetuses, it is necessary to know the hemodynamic modifications of normal fetuses. On this basis, the authors performed a review of fetal hemodynamics evaluated by Doppler velocimetry in the fetal aorta and middle cerebral and umbilical arteries during the second half of pregnancy. The study of fetal vessels by Doppler velocimetry indirectly evaluates the hemodynamic changes occurring in fetuses at risk. In this respect, we emphasize the changes in Doppler velocimetry occurring in fetal anemia, in restricted intrauterine growth, and in normal fetuses.