Effects of intravascular fetal blood transfusion on fetal intracardiac Doppler velocity waveforms

Automated quantitative evaluation of fetal atrioventricular annular plane systolic excursion before and after intrauterine blood transfusion in pregnancies affected by red blood cell alloimmunization

INTRODUCTION

Maternal red blood cell alloimmunization during pregnancy can lead to hemolysis and various degrees of fetal anemia, which can be treated with intrauterine blood transfusion (IUT) to prevent adverse outcomes. Knowledge about fetal myocardial function and adaptation is limited. The aim of the present study was to measure fetal atrioventricular plane displacement before and after IUT and compare these measurements with previously established reference ranges.

MATERIAL AND METHODS

An observational study was conducted on pregnant women affected by red blood cell alloimmunization. Fetal echocardiography was performed before and after IUT. The atrioventricular plane displacement of the left and right ventricular walls and interventricular septum, described as mitral, septal, and tricuspid annular plane systolic excursion (MAPSE, SAPSE, and TAPSE, respectively), was assessed using color tissue Doppler imaging with automated analysis software. A Mann-Whitney U test was used to compare the z scores to the normal mean before and after IUT.

RESULTS

Twenty-seven fetuses were included. The mean z score for pre-IUT MAPSE was significantly increased compared with the reference ranges, +0.46 (95% confidence interval [CI] +0.17 to +0.75; p = 0.039), while the mean z scores for post-IUT SAPSE and TAPSE were significantly decreased, -0.65 (95% CI -1.11 to -0.19; p < 0.001) and -0.60 (95% CI -1.04 to -0.17; p = 0.003), respectively. The difference in atrioventricular plane displacement z scores before and after IUT was statistically significant in all three locations. The median difference between the pre-IUT and post-IUT z scores was -0.66 (95% CI -1.03 to -0.33, p < 0.001) for MAPSE, -1.05 (95% CI -1.43 to -0.61, p < 0.001) for SAPSE, and -0.60 (95% CI -1.19 to -0.01, p = 0.046) for TAPSE.

CONCLUSIONS

This study suggests that atrioventricular plane displacement, when determined using automated analysis software, may represent a quantitative parameter, describing fetal myocardial function and adaptation before and after IUT.

Fetal Cardiac Inflow Characteristics in Response to Fetal Anemia: Based on Fetal Hemoglobin Bart's Disease at Mid-Pregnancy

OBJECTIVES

To identify the inflow (filling time fraction [FTF] and E/A ratio) characteristics of fetuses with anemia, and to evaluate the performance of the inflow markers in predicting the affected fetuses.

METHODS

Fetuses at risk of hemoglobin (Hb) Bart's disease at 17-22 weeks were prospectively recruited to undergo echocardiography before diagnostic cordocentesis. Cardiac Doppler images were digitally stored for off-line blinded measurements of FTF and E/A ratio.

RESULTS

A total of 428 fetuses at risk of Hb Bart's disease were analyzed, including 88 affected fetuses (20.6%). The mean gestational age at the time of diagnosis was 19.43 ± 1.5 weeks. The FTFs in both sides were significantly lower in the affected fetuses, whereas the E/A ratios of both sides were significantly higher in the affected group. According to the receiver operating characteristic curves, the performance of the FTF of the right side in predicting affected fetuses was slightly better than that of the left side (area under curve: 0.707 versus 0.680, P < .001). Likewise, the performance of the E/A ratio of the tricuspid valve was slightly better than that of the mitral valve. Also, FTF was superior to E/A ratio in predicting the affected fetuses.

CONCLUSIONS

New insights leading to a better understanding of the fetal cardiac response to anemia are: 1) the FTFs in both sides were significantly decreased, suggesting some degree of diastolic ventricular dysfunction; 2) the E/A ratios of both sides were significantly increased, indicating volume load; and 3) The inflow parameters may be useful as a new predictor of fetal anemia, especially among pregnancies at risk.

Prenatal Diagnosis of Fetal Heart Failure

Fetal heart failure (FHF) is a condition of inability of the fetal heart to deliver adequate blood flow for tissue perfusion in various organs, especially the brain, heart, liver and kidneys. FHF is associated with inadequate cardiac output, which is commonly encountered as the final outcome of several disorders and may lead to intrauterine fetal death or severe morbidity. Fetal echocardiography plays an important role in diagnosis of FHF as well as of the underlying causes. The main findings supporting the diagnosis of FHF include various signs of cardiac dysfunction, such as cardiomegaly, poor contractility, low cardiac output, increased central venous pressures, hydropic signs, and the findings of specific underlying disorders. This review will present a summary of the pathophysiology of fetal cardiac failure and practical points in fetal echocardiography for diagnosis of FHF, focusing on essential diagnostic techniques used in daily practice for evaluation of fetal cardiac function, such as myocardial performance index, arterial and systemic venous Doppler waveforms, shortening fraction, and cardiovascular profile score (CVPs), a combination of five echocardiographic markers indicative of fetal cardiovascular health. The common causes of FHF are reviewed and updated in detail, including fetal dysrhythmia, fetal anemia (e.g., alpha-thalassemia, parvovirus B19 infection, and twin anemia-polycythemia sequence), non-anemic volume load (e.g., twin-to-twin transfusion, arteriovenous malformations, and sacrococcygeal teratoma, etc.), increased afterload (intrauterine growth restriction and outflow tract obstruction, such as critical aortic stenosis), intrinsic myocardial disease (cardiomyopathies), congenital heart defects (Ebstein anomaly, hypoplastic heart, pulmonary stenosis with intact interventricular septum, etc.) and external cardiac compression. Understanding the pathophysiology and clinical courses of various etiologies of FHF can help physicians make prenatal diagnoses and serve as a guide for counseling, surveillance and management.

Fetal cardiac function at intrauterine transfusion assessed by automated analysis of color tissue Doppler recordings

BACKGROUND

Fetal anemia is associated with a hyperdynamic circulation and cardiac remodeling. Rapid intrauterine transfusion (IUT) of blood with high hematocrit and viscosity into the umbilical vein used to treat this condition can temporarily further affect fetal heart function. The aim of this study was to evaluate the short-term changes in fetal myocardial function caused by IUT using automated analysis of cine-loops of the fetal heart obtained by color tissue Doppler imaging (cTDI).

METHODS

Fetal echocardiography was performed before and after IUT. cTDI recordings were obtained in a four-chamber view and regions of interest were placed at the atrioventricular plane in the left ventricular (LV), right ventricular (RV) and septal walls. Myocardial velocities were analyzed by an automated analysis software to obtain peak myocardial velocities during atrial contraction (Am), ventricular ejection (Sm), rapid ventricular filling (Em) and Em/Am ratio was calculated. Myocardial velocities were converted to z-scores using published reference ranges. Delta z-scores (after minus before IUT) were calculated. Correlations were assessed between variables and hemoglobin before IUT.

RESULTS

Thirty-two fetuses underwent 70 IUTs. Fourteen were first time transfusions. In the LV and septal walls, all myocardial velocities were significantly increased compared to normal values, whereas in the RV only Sm was increased before IUT (z-scores 0.26-0.52). In first time IUTs, there was a negative correlation between LV Em (rho = - 0.61, p = 0.036) and LV Em/Am (rho = - 0.82, p = 0.001) z-scores and hemoglobin before IUT. The peak myocardial velocities that were increased before IUT decreased, whereas LV Em/Am increased significantly after IUT.

CONCLUSIONS

This study showed that peak myocardial velocities assessed by cTDI are increased in fetuses before IUT reflecting the physiology of hyperdynamic circulation. In these fetuses, the fetal heart is able to adapt and efficiently handle the volume load caused by IUT by altering its myocardial function.

Cardiac function and dysfunction in the fetus

Evaluation of fetal cardiac function is one of the most important components of fetal echocardiography. Fetal cardiac dysfunction is closely linked to risk of intrauterine fetal demise, in many, but not all cases is indicative of worse postnatal prognosis and may prompt the use of medications or interventions to optimize outcomes. There may be implications for termination versus continuation of pregnancy, an indication for early delivery, a change in location and even mode of delivery. In extreme cases, fetal cardiac dysfunction may prompt prenatal or early neonatal listing for cardiac transplantation. There are several important differences between the fetal and postnatal circulatory physiology which affect echocardiographic assessment of cardiac dysfunction. In this review, we examine the echocardiographic findings according to their underlying pathophysiology with reference to common causes.

Fetal Laboratory Medicine: On the Frontier of Maternal–Fetal Medicine

BACKGROUND

Emerging antenatal interventions and care delivery to the fetus require diagnostic support, including laboratory technologies, appropriate methodologies, establishment of special algorithms, and interpretative guidelines for clinical decision-making.

CONTENT

Fetal diagnostic and therapeutic interventions vary in invasiveness and are associated with a spectrum of risks and benefits. Fetal laboratory assessments are well served by miniaturized diagnostic methods for blood analysis. Expedited turnaround times are mandatory to support invasive interventions such as cordocentesis and intrauterine transfusions. Health-associated reference intervals are required for fetal test interpretation. Fetal blood sampling by cordocentesis carries substantial risk and is therefore performed only when fetal health is impaired, or at risk. When the suspected pathology is not confirmed, however, normative fetal data can be collected. Strategies for assurance of sample integrity from cordocenteses and confirmation of fetal origin are described. After birth, definitive assessment of prenatal environmental and/or drug exposures to the fetus can be retrospectively assessed by analysis of meconium, hair, and other alternative matrices. A rapidly advancing technology for fetal assessment is the use of fetal laboratory diagnostic techniques that use cell-free fetal DNA collected from maternal plasma, and genetic analysis based on molecular counting techniques.

SUMMARY

Developmental changes in fetal biochemical and hematologic parameters in health and disease are continually delineated by analysis of our collective outcome-based experience. Noninvasive technologies for fetal evaluation are realizing the promise of lower risk yet robust diagnostics; examples include sampling and analysis of free fetal DNA from maternal blood, and analysis of fetal products accessible at maternal sites. Application of diagnostic technologies for nonmedical purposes (e.g., sex selection) underscores the importance of ethical guidelines for new technology implementation.

Prediction of severe fetal anemia in red blood cell alloimmunization after previous intrauterine transfusions

OBJECTIVE

This study was undertaken to determine the detection of fetal anemia and false-positive rates by fetal middle cerebral artery peak systolic velocity (MCA-PSV) and the estimated daily decrease of hemoglobin (Hb) in red blood cell alloimmunized pregnancies that had previous fetal transfusions.

STUDY DESIGN

We examined the relation between MCA-PSV measured before cordocentesis, and fetal Hb at the time of the second (n = 42) and third (n = 31) intrauterine blood transfusions. In addition, the daily Hb drop between the transfusions was calculated.

RESULTS

The MCA-PSV provided significant prediction of severe anemia (Hb deficit > or = 6 g/dL) for the second but not for the third transfusion. Detection of 95% of severely anemic fetuses was achieved with a false-positive rate of 37% for the second transfusion and 90% for the third, compared with 14% in our previous study for the first transfusion. In patients who had received 2 previous transfusions, the only significant predictor of fetal anemia was the estimation of the Hb from the measured posttransfusion Hb after the second transfusion and the assumption that the rate of decrease in fetal Hb is 0.3 g/dL per day.

CONCLUSION

Prediction of severe fetal anemia after one transfusion is less accurate than in nontransfused fetuses. The MCA-PSV is not useful in predicting severe anemia in fetuses that already had 2 previous transfusions.

An Audit of Outcome in Intravascular Transfusions Using the Intrahepatic Portion of the Fetal Umbilical Vein Compared to Cordocentesis

INTRODUCTION

Maternal red cell alloimmunization is a potential cause of perinatal morbidity and mortality. The outcome of severe disease has been transformed by the use of in-utero and particularly, fetal intravascular transfusion. In the majority of instances this is performed by cordocentesis. However, this cohort study represents the experience in a large tertiary referral centre in performing fetal intravascular transfusions via the intrahepatic vein (IHV).

METHODS

Over an 8-year period, 1997-2004, 221 in-utero transfusions (IUT) were performed for rhesus disease in 66 pregnancies. 86% had severe fetal anaemia caused by anti-D, 10.6% by anti-Kell and 3.4% by anti-c. The median maternal age of the cohort was 31 years (range 19-43). The median gestation at initial IUT was 25 weeks (interquartile range (IQR) 23-29 weeks).

RESULTS

A median number of three IUT were performed in each fetus (IQR 2-5) with a median haemoglobin at first fetal blood sampling of 7.3 g% (IQR 4.6-8.8 g%) (73% < or =5 SD and 27% < or =2 SD). Of the total intravascular transfusions, 170 were performed via the IHV (71.7%), 33 via cordocentesis (13.9%) and 1 by intracardiac puncture (0.5%). There were 'transient' bradycardias complicating 4.1% of all transfusions and amniorrhexis following 1.4%. 92% of babies were live born at a median gestation of 34 weeks (range 21-38) with a birth weight centile of 50 (range 3-90). There was no significant difference in intravascular transfusion complication rate when the procedure was performed via the IHV (7.6%) as compared to cord root puncture (3.0%) (Fisher's exact test, p < 0.47).

CONCLUSION

IUT performed by fetal IHV puncture is safe and carries no excess morbidity when performed for severe rhesus disease.

Fetal cardiac contractility before and after intrauterine transfusion

OBJECTIVE

To evaluate the effect of fetal anemia and intrauterine transfusion on ventricular shortening fraction.

METHODS

The end-diastolic and end-systolic transverse dimensions of the left and right ventricles were obtained using M-mode ultrasonography. The shortening fractions of both ventricles were calculated at three time points: before, immediately after and one day after intrauterine transfusion. The blood volume given at intrauterine transfusion was expressed as a percentage of estimated fetoplacental blood volume.

RESULTS

Complete measurements were obtained from 49 transfusions in 23 fetuses. Intrauterine transfusion was performed at a median gestational age of 31 (range, 19-35) weeks. Median hemoglobin concentration before and after intrauterine transfusion was 7.9 (range, 2.7-13.7) g/dL and 14.3 (range, 12.7-16.1) g/dL, respectively. Both left and right ventricular shortening fractions differed significantly between the three time points. Left ventricular shortening fraction decreased immediately after transfusion in 43 (88%) of the 49 procedures. Right ventricular shortening fraction decreased immediately after transfusion in 42 (86%) of the 49 procedures. At the first intrauterine transfusion, there was only a weak correlation between the decrease in shortening fraction of both ventricles and the transfused volume (left: R(2) = 0.15; P = 0.20/right: R(2) = 0.005; P = 0.81).

CONCLUSION

Transfusion significantly decreases the shortening fraction of both ventricles of the fetal heart. There is, however, little correlation between the decrease in shortening fraction and the volume of red cells given at intrauterine transfusion. Published by John Wiley & Sons, Ltd.

Diagnosis, surveillance, and treatment of the anemic fetus using middle cerebral artery peak systolic velocity measurement

The in utero course of the anemic fetus has improved dramatically, owing to early diagnosis and cordocentesis transfusion. In utero invasive procedures such as amnio- and cordocentesis have become important modalities in the evaluation and treatment of anemic fetuses. However, they carry risks for both the mother and fetus. A valid and sensitive noninvasive means of following the anemic fetus is the evaluation of changes in the middle cerebral artery peak systolic flow velocity (MCA-PSV). This is a sensitive tool for both the evaluation of fetal anemia and response to treatment. Intracerebral vessels respond earliest to the fetal anemic state, and are readily accessible for ultrasound examination. We describe the methodology and evolving clinical applications of MCA-PSV measurement in the fetus, through an overview of the literature describing the development and application of MCA-PSV measurement in fetuses at risk of fetal anemia of various immune and nonimmune etiologies, illustrated by index cases from our center. MCA-PSV measurement is essential in the diagnosis, evaluation, and management of cases of fetal anemia. The use of this modality lessens the need for invasive procedures. The method is readily accessible and should be integrated into the repertoire of all obstetric ultrasound centers.

Predicting the severity of fetal anemia using time-domain measurement of volume flow in the fetal aorta

OBJECTIVES

To assess the value of fetal aortic time-domain measurement of volume flow (using color velocity imaging quantification (CVI-Q)) in predicting the severity of fetal anemia.

METHODS

This was a prospective observational study, in which 24 pregnant women with suspected fetal anemia due to rising anti-red blood cell antibody titers underwent cordocentesis. The fetal aortic time-domain volume flow was measured before fetal blood sampling for fetal hemoglobin investigation. We examined the correlation between increased fetal aortic time-domain volume flow (>2 SD for gestational age) and fetal anemia (hemoglobin level <2 SD for gestational age).

RESULTS

Seventeen fetuses had anemia, and seven had normal hemoglobin. There was a strong correlation between the increase in fetal aortic time-domain volume flow and the drop in hemoglobin value (r = 0.81; P < 0.01). The sensitivity of this technique to predict fetal anemia was 81.3% and the specificity was 71.4%. The mean increase over time in aortic CVI-Q in anemic fetuses was 323.2 mL/min (95% CI, 200.1 to 446.4) compared with 86.9 mL/min (95% CI, -17.7 to 191.5) in the non-anemic group (P = 0.004).

CONCLUSION

Fetal aortic time-domain measurement of volume flow is significantly increased in cases of fetal anemia due to red-cell alloimmunization. These findings can be used to improve the sensitivity, specificity and positive predictive value of the non-invasive techniques used to predict fetal anemia, and may help in the selection of pregnancies that require cordocentesis and transfusion.

Evaluation of fetal cardiac contractility by two-dimensional ultrasonography

OBJECTIVE

Evaluation of fetal cardiac contractility by two-dimensional ultrasonography and construction of nomograms of area shortening fraction, end-diastolic area and end-systolic area of fetal cardiac ventricles during uncomplicated pregnancy.

MATERIALS AND METHODS

Fetal echocardiography was performed on 160 pregnant women between 14 and 28 weeks' gestation. Measurements were taken on the four-chamber view. The area of each ventricle was measured by tracing the endocardium at the end of systole and at the end of diastole. Area shortening fraction was calculated by the following formula: SF = (Ad - As)/Ad (SF--area shortening fraction, Ad--end-diastolic ventricular area, As--end-systolic ventricular area).

RESULTS

A statistically significant increase in normal fetal area shortening fraction, end-diastolic area and end-systolic area of both ventricles with advancing gestational age was established. There were no significant differences in the area shortening fraction between right and left ventricles.

CONCLUSIONS

Area shortening fraction shows good correlation with gestational age. Nomogram of area shortening fraction, end-diastolic area and end-systolic area of both ventricles can be used as the reference for evaluation of ventricle size and cardiac contractility in normal and pathological cases.

Anti-E alloimmunization in pregnancy: management dilemmas

Compared to anti-D alloimmunization, anti-E alloimmunization is a less common cause of hemolytic diseases of the newborn. Being a less potent immunogen, clinical manifestations of anti-E alloimmunization are more variable and usually of less severity. However, the clinical obstetric management of these cases of anti-E alloimmunization is just as challenging. We report here the management of a patient with anti-E alloimmunization to illustrate the controversies of invasive and non-invasive monitoring in the management of such cases.

Prediction of fetal anaemia

The perinatal outcome of the anaemic fetus has dramatically improved over the last 20 years, as a result of early recognition of the problem and treatment by intrauterine transfusion. Traditionally assessment of the anaemic fetus relied on obstetric history and maternal antibody titre, which proved to be inadequate tests to accurately predict fetal condition. More recently, invasive testing with techniques such as amniocentesis and cordocentesis have allowed a more accurate evaluation of the degree of anaemia, while at the same time enabling transfusion to take place. Such techniques are not without danger, with perinatal loss and fetomaternal haemorrhage being significant risks. The clinical community has therefore sought to find accurate, non-invasive methods for assessing the degree of fetal anaemia, thereby reducing the number of unnecessary invasive procedures, while at the same time providing more precise data on the quantity and timing of the transfusion. Recent publications focusing on the diagnosis and management (including plasmapheresis, immunoglobulins and intrauterine transfusion) of fetal anaemia will be discussed.

Sonographic methods to detect fetal anemia in red blood cell alloimmunization

Published reports, case studies, and articles from the English language regarding ultrasonographic detection of fetal anemia in red blood cell alloimmunization were obtained from a MEDLINE search from 1966 to November 1999 using the keywords Rh disease, hemolytic disease of the newborn, ultrasound, and Doppler flow studies and combinations thereof. All articles were cross-referenced. Ultrasound techniques including early findings associated with immune hydrops fetalis, multiple morphologic ultrasound markers, and Doppler flow studies that have been used to detect fetal anemia are reviewed and critically evaluated. Noninvasive sonographic techniques may reduce the number of invasive procedures that traditionally are used to follow fetuses at risk for anemia and decrease the associated risks from these procedures.

Left ventricular hemodynamics in anemic fetal lambs

OBJECTIVE

To assess the left ventricular determinants of cardiac output in 12 chronically instrumented fetal lambs, six of which where made anemic.

METHODS

Twelve, singleton pregnant ewes were instrumented between 123-126 days gestation and chronic catheters placed in-situ. In six fetal lambs, isovolemic fetal anemia was induced (reducing the hematocrit from a mean of 35% to 20%). In a prospective study, absolute 'beat-to-beat' LV volumes and pressures were obtained (gestational age 131-134 days) using a conductance catheter method and a comparison made with non-anemic fetal lambs.

RESULTS

The group of anemic fetuses (n = 6) had a significantly reduced hematocrit as compared to the control group (37% decrease: mean difference--13.4%; P < 0.001). The arterial blood gases of the two groups were not statistically different, with the exception of the pO2 and oxygen content which were significantly lower in the anemic group (P < 0.05). There was no significant change in fetal heart rate, LV preload (as assessed by venous pressure, end-diastolic volume and pressure) or mean arterial pressure between the anemic and control groups. However, a 75% increase in LV stroke volume was observed in the anemic fetal lambs (P < 0.05), secondary to a 61% fall in LV afterload (P < 0.05). There was no significant change in inherent myocardial contractility of the LV, although this did increase to approach statistical significance in the anemic group (P = 0.056). The diastolic time interval was increased by 22% in the anemic fetus, possibly allowing prolonged LV filling time. The indices measuring LV relaxation (Tau and dP/dtmin) were not significantly different in either group.

CONCLUSIONS

This is the first study to report absolute left ventricular volumes in the anemic ovine fetus and the relationship of these data to LV pressure during the cardiac cycle. The model used produces a state of moderately severe, non-hydropic, isovolemic, fetal anemia consistent with those previously described. Although the anemic state was not prolonged, an observed increase in LV stroke volume (which is predominantly due to a decrease in afterload) has been described.

Potential value of fetal echocardiography in the differential diagnosis of twin pregnancy with presence of polyhydramnios-oligohydramnios syndrome

OBJECTIVE

Our purpose was to establish whether index values of cardiac performance could discriminate between the twin-twin transfusion syndrome and placental insufficiency as the etiology of the polyhydramnios-oligohydramnios sequence in monochorionic diamniotic twins.

STUDY DESIGN

Thirteen monochorionic diamniotic twin pregnancies with ultrasonographic evidence of polyhydramnios-oligohydramnios sequence had a complete echocardiography. The etiology was confirmed postnatally: placental insufficiency in eight pairs and the twin-twin transfusion syndrome in five. Intertwin comparisons were made for the following cardiac parameters: cardiothoracic index, end-diastolic thickness of the ventricular walls and septum, aortic and pulmonary artery Doppler peak velocities, ejection and acceleration times, left ventricular shortening fraction, and combined cardiac output and output indexed to fetal weight.

RESULTS

All five recipient twins had thickened ventricular walls. The left ventricular shortening fractions and outputs were significantly increased in the donor twin with twin-twin transfusion syndrome and normal in placental insufficiency.

CONCLUSION

In twin-twin transfusion syndrome the donor twin shows evidence of a hyperdynamic cardiac state. Intertwin comparison of cardiac parameters, especially the left ventricular shortening fraction, can be considered a useful tool in diagnosing the different etiologies of the polyhydramnios-oligohydraminos sequence.

Cardiac and extracardiac flows in discordant twins

OBJECTIVE

Our purpose was to evaluate Doppler-detectable differences in the fetal circulation of discordant twins with a growth defect resulting from either placental insufficiency or twin-to-twin transfusion syndrome.

STUDY DESIGN

Serial weekly Doppler recordings were performed for at least 3 weeks preceding delivery in 15 pairs of dichorionic twins (group A) in which the smaller twin had fetal distress (i.e., antepartum fetal heart rate late decelerations) and in 10 pairs of diamniotic and monochorionic twins (group B) in which the diagnosis of twin-to-twin transfusion syndrome was confirmed postnatally. Doppler recordings were obtained from umbilical artery, descending aorta, and middle cerebral artery, and the pulsatility index values were calculated. Furthermore, peak velocity from cardiac outflow tract and the percent of reverse flow in the inferior vena cava were calculated. For all these index values the intertwin differences (delta value) were calculated by subtracting the values obtained in the larger twin with those of the smaller twin.

RESULTS

In group A significant changes of delta values were evidenced for all the parameters tested. In particular, delta values of pulsatility index from the umbilical artery and descending aorta progressively increased approaching the occurrence of late decelerations, whereas the delta value for the middle cerebral artery reached a nadir 2 weeks before delivery. Similarly, delta values of peak velocity from outflow tracts significantly decreased, whereas those of the percent reverse flow in the inferior vena cava increased during the time considered. In group B fetuses no significant intertwin differences in pulsatility index values were evidenced in the vessels investigated, resulting in absence of modifications in delta values during the time interval considered. Moreover, significant changes were found in delta values of both the peak velocity from the outflow tract and the percent of reverse flow in the inferior vena cava. However, these changes were limited to the last recording, where the former delta value increased and the latter decreased.

CONCLUSIONS

Serial Doppler recordings may show hemodynamic changes in the fetal circulation of discordant twins. Different trends occur according to the underlying pathophysiologic mechanisms of the growth defect. The knowledge of these temporal changes may be useful in the management of such fetuses.

Umbilical venous pressure in normal, growth-retarded, and anemic fetuses

OBJECTIVE

Our purpose was to establish a reference range with gestation for umbilical venous blood pressure and to examine possible changes in intrauterine growth retardation and red blood cell isoimmunization.

STUDY DESIGN

Umbilical venous pressure was measured at cordocentesis in pregnancies complicated by intrauterine growth retardation (n = 20) and red blood cell isoimmunization (n = 61) both before and after intravascular fetal blood transfusion. The values were compared with a reference range that was constructed from the study of 111 pregnancies undergoing prenatal diagnosis at 18 to 40 weeks' gestation.

RESULTS

In the control group the mean umbilical venous pressure increased significantly with gestation. In the growth-retarded fetuses umbilical venous pressure was higher, normal, or decreased, and there was no significant association between umbilical venous pressure and either fetal size or degree of acidemia. In the pregnancies complicated by red blood cell isoimmunization umbilical venous pressure increased with anemia but decreased to normal in the most severely anemic and hydropic fetuses. After intravascular blood transfusion umbilical venous pressure in proportion to the improvement in fetal hemoglobin concentration.

CONCLUSION

Umbilical venous pressure is not the equivalent of central venous pressure but reflects both left and right heart function and placental resistance.

Analysis of factors influencing ventricular filling patterns in fetuses of type I diabetic mothers

In an effort to determine the factors influencing the abnormal ventricular filling patterns of fetuses of type I diabetic mothers, Doppler flow velocity waveforms were recorded from fetal atrioventricular valves in 37 pregnancies complicated by type I diabetes immediately before an elective cesarean section. The ratio between the peak velocities during early passive ventricular filling and active atrial filling was calculated at the level of both atrioventricular valves and related to different factors including ventricular chamber wall thickness, heart rate, umbilical vein hematocrit and time to peak velocities values obtained at the outflow tract. Multiple stepwise regression demonstrated that the interventricular wall thickness, heart rate and hematocrit values significantly and independently affected the ratios between early and active ventricular filling from mitral and tricuspid valves. As a consequence all these factors should be taken into account in the interpretation of atrioventricular Doppler indices.

Fetal cardiac function in intrauterine growth retardation

Blood-flow velocity waveforms are altered in several peripheral vascular beds of fetuses whose intrauterine growth is retarded because of placental insufficiency. We investigated these concomitant changes in cardiac function. Color and pulsed Doppler echocardiographic recordings were performed in 124 fetuses with intrauterine growth retardation. These fetuses were free of structural and chromosomal abnormalities and were characterized by increased umbilical artery resistance and reduced middle cerebral artery resistance. Twenty-four of these fetuses were also studied at weekly intervals until the onset of antepartum late heart rate decelerations. Blood-flow velocity waveforms were obtained from the aortic and pulmonary valves, and the following variables were measured: peak systolic velocity, time to peak velocity, the product of time velocity integral multiplied by heart rate, left and right cardiac output, and the right/left ratios of the product of time velocity integrals multiplied by heart rate and cardiac output. When compared with previously established norms, both aortic and pulmonary peak systolic velocities and pulmonary time to peak velocity were reduced; aortic time to peak velocity increased. Left cardiac output and the product of the aortic time velocity integral multiplied by the heart rate increased and right cardiac output and the product of the pulmonary time velocity integral multiplied by the heart rate decreased, resulting in reduced right/left ratios. In the 24 fetuses studied longitudinally, time to peak velocities and the right/left flow ratios remained stable. However, aortic and pulmonary peak velocities and cardiac output declined significantly in contrast to an expected rise with advancing gestation. The fall in cardiac output and aortic and pulmonary peak velocities was directly related to umbilical artery pH at birth. This study provides evidence of a modified cardiac function that seems to deteriorate progressively with the advancing gestation of fetuses with intrauterine growth retardation.