Flow velocity waveforms of the vascular system in the anemic fetus before and after intravascular transfusion for severe red blood cell alloimmunization

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.

Independent influences of maternal obesity and fetal sex on maternal cardiovascular adaptation to pregnancy: a prospective cohort study

Background/Objectives

Successful pregnancy requires the de novo creation of low-resistance utero-placental and feto-placental circulations and incomplete remodeling of this vasculature can lead to maternal or fetal compromise. Maternal BMI and fetal sex are known to influence vascular compliance and placental development, but it is unknown if these are independent or synergistic effects. Here we aim to investigate the impact of maternal obesity, fetal sex, and any interaction thereof on maternal cardiovascular adaptation to pregnancy, by assessing the physiological drop of uterine artery doppler pulsatility (UtA-PI) and umbilical artery doppler pulsatility index (UA-PI) over gestation.

Subjects/Methods

Nulliparous women with a singleton pregnancy participating in a prospective cohort study (n = 4212) underwent serial UtA-PI and UA-PI measurements at 20-, 28- and 36-weeks gestation. Linear mixed regression models were employed to investigate the influence of maternal BMI, fetal sex and interactions thereof on the magnitude of change in UtA-PI and UA-PI.

Results

Throughout gestation, UtA-PI was higher for male fetuses and UA-PI was higher for female fetuses. The physiological drop of UtA-PI was significantly smaller in overweight (change −24.3% [95%CI −22.3, −26.2]) and obese women (change −21.3% [−18.3, −24.3]), compared to normal-weight women (change −25.7% [−24.3, −27.0]) but did not differ by fetal sex. The physiological drop in UA-PI was greater for female than male fetuses (–32.5% [−31.5, −33.5] vs. −30.7% [−29.8, −31.7]) but did not differ by maternal BMI. No interactions between maternal BMI and fetal sex were found.

Conclusions

Maternal cardiovascular adaptation to pregnancy is independently associated with maternal BMI and fetal sex. Our results imply sexual dimorphism in both maternal cardiovascular adaptation and feto-placental resistance.

Fetal anemia

The diagnosis and management of fetal anemia has been at the forefront of advances in the fields of fetal physiology, immunology, fetal imaging, and fetal therapy among others. Alloimmunization and parvovirus infection are the leading cause of fetal anemia in the United States. The middle cerebral artery peak systolic velocity (MCA-PSV) diagnoses fetal anemia. Its discovery is considered one of the most important achievements in fetal medicine. Accumulation of experience in recent years as well as refinement of surgical techniques have led to safer invasive procedures. It is expected that long term follow-up of affected pregnancies, continues to reflect all these improvements in care. It is also expected that treatment of other less common causes of fetal anemia becomes more frequently reported and that the management principles of fetal anemia are successfully applied to other fetal pathologies.

Variations from morning to afternoon of middle cerebral and umbilical artery blood flow, and fetal heart rate variability, and fetal characteristics in the normally developing fetus

OBJECTIVE

To determine if there are changes in maternal uterine blood flow, fetal brain blood flow, fetal heart rate variability, and umbilical blood flow between morning (AM) and afternoon (PM) in healthy, uncomplicated pregnancies.

STUDY DESIGN

In this prospective study, 68 uncomplicated singleton pregnancies (mean 35 + 0.7 weeks gestation) underwent a standard observational protocol at both 08:00 (AM) and 13:30 (PM) of the same day. This protocol included Doppler measurements of uterine, umbilical, and fetal middle cerebral artery (MCA) volume flow parameters (flow, HR, peak systolic velocity [PSV], PI, and RI) followed by computerized cardiotocography. Standard descriptive statistics, χ² and t tests were used where appropriate. P < .05 was considered significant.

RESULTS

A significant increase in MCA flow and MCA PSV was observed in the PM compared to the AM. This was accompanied by a fall in MCA resistance. Higher umbilical artery resistance indices were also observed in the PM compared to AM. In contrast, fetal heart rate characteristics, maternal uterine artery Doppler flow and resistance indices did not vary significantly between the AM and PM.

CONCLUSION

In normal pregnancies, variations in fetal cerebral and umbilical blood flow parameters were observed between AM and PM independent of other fetal movements or baseline fetal heart rate. In contrast, uterine flow parameters remained stable across the day. These findings may have implications for the use of serial Doppler parameters used to guide clinical management in high-risk pregnancies.

Relationship between Cardiofemoral Index and the plasma concentration of brain natriuretic peptide in anemic fetuses associated with Rh alloimmunization

BACKGROUND

Fetal anemia is a common result of alloimmunization and is an important cause of fetal congestive heart failure resulting in heart dilation. Fetuses suspected of having heart failure present a higher Cardiofemoral Index and an increase in plasma BNP levels, because the cardiac hormonal system is activated by increased heart wall stretch due to increased left ventricular volume and pressure overload.

METHODS

Our group studied 33 pregnant women (22-31 weeks' gestation at the first cordocentesis) referred for intrauterine fetal transfusion due to severe red blood cells isoimmunization. Up to 6 h prior to each cordocentesis, all fetuses were submitted to ultrasonography measurements where the Cardiofemoral Index was calculated. Samples of blood from the umbilical vein were collected for hemoglobin concentration and blood gas measurements. Plasma levels of BNP were determined with the use of plasma that had previously been frozen and thawed once. Plasma BNP was measured by radioimmunoassay. Pearson's correlation test and regression analysis were used to determine the association between the plasma concentration of BNP and the Cardiofemoral Index of the anemic fetuses with RH alloimmunization.

RESULTS

Anemia was severe in 17 (50%) fetuses, mild in 9 (26.47%) and in 8 patients (23.53%) the fetuses were not anemic; hemoglobin ranged from 3.10 to 15.70 g/dl. The Cardiofemoral Index ranged from 0.43 to 0.87 and it was altered (>or=0.59) in 23 fetuses. A significant positive correlation was observed between BNP plasma fetal concentration and Cardiofemoral Index (Pearson r=0.61, P<0.0001).

CONCLUSIONS

These results suggest that fetal plasma concentration of BNP may increase in fetuses with heart dilation leading to a positive association between Cardiofemoral Index and plasma concentration of BNP.

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.

The effect of fetal behavioral states on middle cerebral artery peak systolic velocity

OBJECTIVE

This study was undertaken to determine whether is there a difference in the middle cerebral artery peak systolic velocity (MCA PSV) between active and resting behavioral states in healthy fetuses aged 30 to 32 weeks.

METHODS

MCA blood flow was measured by pulsed Doppler sonography 3 times during each fetal behavioral state (active and resting). The average during active state was compared during the resting state. Statistical analysis was performed by paired t test.

RESULTS

During the fetal active state, there was a significant increase in the mean PSV (51.59 cm/s vs 46.95 cm/s, P < .0001) and mean end-diastolic velocity (9.59 cm/s vs 7.98 cm/s, P=.0015), and a significant decrease in the mean pulsatility index (PI) (2.07 vs 2.19, P=.0226) and the mean resistance index (0.83 vs 0.85, P=.0481).

CONCLUSION

Healthy preterm fetuses have a significantly higher MCA PSV during the active state. Activity state should be considered when interpreting MCA Doppler indices.

Doppler assessment of the fetal cerebral hemodynamic response to moderate or severe maternal anemia

OBJECTIVE

The purpose of this study was to evaluate the fetal vascular adaptation to moderate and severe maternal anemia.

STUDY DESIGN

Biometry; amniotic fluid index; uterine, cerebral, and umbilical Doppler; and maternal hemoglobin level were measured at admission and 8 days after treatment.

RESULTS

Group 1 consisted of 16 pregnancies (maternal hemoglobin level, 6.9 +/- 0.6 g/100 mL); group 2 consisted of 23 pregnancies (maternal hemoglobin level, 5 +/- 0.6 g/100 mL). At admission the cerebral and cerebral/umbilical Doppler indexes, amniotic index, and biometry were lower in group 2. The uterine index was normal in both groups. An abnormal fetal heart rate was found in group 2 only (48%). At day 8, maternal hemoglobin level and amniotic index increased more in group 2 than in group 1. The cerebral index and the cerebral-to-umbilical resistance ratio increased only in group 2. The abnormal fetal heart rate disappeared in group 2.

CONCLUSION

Only severe maternal anemia (maternal hemoglobin level, <6 mg/L) triggered fetal cerebral vasodilation and reduced amniotic volume.

Middle cerebral artery Doppler study in fetuses with homozygous alpha-thalassaemia-1 at 12-13 weeks of gestation

OBJECTIVE

Fetuses affected by homozygous alpha-thalassaemia-1 are anaemic from the first trimester of pregnancy. We investigated middle cerebral artery Doppler velocimetry in these affected fetuses at 12-13 weeks of gestation to assess its use in predicting fetal anaemia.

METHODS

Women referred for the prenatal diagnosis of homozygous alpha-thalassaemia-1 before 14 weeks of gestation were recruited. All fetuses underwent pulsed Doppler examinations following colour flow mapping at 12 or 13 weeks of gestation. Homozygous alpha-thalassaemia-1 was diagnosed by DNA or haemoglobin study. The middle cerebral artery Doppler indices were compared between the affected fetuses and fetuses unaffected by homozygous alpha-thalassaemia-1.

RESULTS

Between 1998 and 2000, 80 eligible women were recruited. Of these, 19 fetuses were affected by homozygous alpha-thalassaemia-1. Two of them showed hydropic changes at the time of Doppler study. The affected fetuses had significantly higher middle cerebral artery peak systolic velocity (V(max)) (36% increase) and time-averaged maximum velocity (V(tamx)) (33% increase).

CONCLUSION

The increase of cerebral blood flow in affected fetuses is consistent with our previous finding of an increased forward flow in the ductus venosus, cardiac dilatation and an increase of cardiac output to preferentially shunt more oxygenated blood to the brain as a compensatory mechanism. However, extensive overlap of the middle cerebral artery flow velocity values between affected and unaffected fetuses precludes its use in predicting anaemia at 12-13 weeks' gestation.

Assessment of blood flow velocity waveforms of the pulmonary circulation by multigate spectral Doppler scanning and traditional pulsed Doppler ultrasonography

OBJECTIVE

To assess (1) pulmonary artery and peripheral pulmonary blood flow by using a multigate spectral Doppler system and standard pulsed color Doppler ultrasonography and (2) the reproducibility of peripheral pulmonary artery blood flow velocity waveforms.

METHODS

Thirty-three women were enrolled in the study Fetal pulmonary artery flow velocity waveforms were investigated by multigate spectral Doppler scanning and traditional pulsed Doppler ultrasonography plus color flow mapping. To establish the relationship between these 2 methods, we calculated the correlation coefficient, coefficient of variation, and limits of agreement.

RESULTS

The 2 methods were not significantly correlated. The range of measurement agreement for these 2 methods suggests that there is a significant difference between the main and peripheral pulmonary artery blood flow, and the difference should be taken into account in the interpretation of Doppler flow velocity studies of the pulmonary artery.

CONCLUSIONS

Multigate spectral Doppler scanning with power Doppler imaging may be a better way to assess the average flow impedance in a highly vascularized organ. This technique supplies a large number of Doppler signals in the region of interest and offers a quantified range of Doppler measurements, improving our understanding of fetal hemodynamics.

Prediction of fetal anemia with Doppler measurement of the middle cerebral artery peak systolic velocity in pregnancies complicated by maternal blood group alloimmunization or parvovirus B19 infection

OBJECTIVES

To confirm the relationship between the middle cerebral artery peak systolic velocity (MCA PSV) and hemoglobin values in fetuses at risk for anemia (due to maternal blood group alloimmunization or parvovirus B19 infection) and to investigate the clinical value of this method in the management of these pregnancies regardless of previous transfusions.

SUBJECTS AND METHODS

Forty singleton pregnancies, 30 affected by alloimmunization and 10 by intrauterine parvovirus B19 infection, were referred to our tertiary center between 1998 and 2000. All cases underwent Doppler measurement of the MCA PSV immediately before fetal blood sampling and just before and after intrauterine transfusion. Hemoglobin determination was always performed after diagnostic cordocentesis, before starting and after terminating fetal transfusion.

RESULTS

Overall, we performed 165 fetal blood samplings (hemoglobin values) and obtained 165 corresponding MCA PSV values, 140 in pregnancies complicated by red-cell alloimmunization and 25 by parvovirus B19 infection. In order to adjust for the effect of gestational age on the measurements, the data were expressed in multiples of the median (MoM). We found a good correlation between MCA PSV MoM and Hb MoM in both groups (alloimmunization, r2 = 0.6; y = 2.21 - 1.41 x + 0.24 x 2; parvovirus infection, r2 = 0.68; y = 2.09 - 0.58 x - 0.16 x 2). The reduction of post-transfusion MCA PSV values was statistically significant ( P < 0.0001). Using a threshold of 1.29 for MoM PSV, the sensitivity and the specificity of MCA pulsatility indices on pretransfusion values in predicting any degree of fetal anemia (Hb < or = 0.84 MoM) were 73.1% and 81.5% in the alloimmunization group and 100% and 100% in the parvovirus infection group, respectively.

CONCLUSION

We can confirm the presence of an inverse correlation between MCA PSV measurements and hemoglobin values in fetuses at risk for anemia due to maternal blood group alloimmunization and fetal parvovirus B19 infection. The MCA PSV is a reliable method for the prediction of anemia not only in fetuses before the first intrauterine transfusion, but also in those which have undergone one or more transfusions, with good sensitivity and specificity in both groups of fetuses at risk.

Middle cerebral artery peak systolic velocity in the prediction of fetal anemia

OBJECTIVE

The fetal middle cerebral artery peak systolic velocity (MCA PSV) has been suggested as a potential test to predict the fetal hematocrit level. We tested the hypothesis that a low fetal hematocrit is associated with an increase in MCA PSV in a prospective study of normal and alloimmunized pregnancies.

METHODS

Fetal hematocrit and MCA PSV were obtained in 26 alloimmunized fetuses, immediately before their first fetal blood transfusions between 15 and 35 weeks. Results were compared with the MCA PSVs from 170 control fetuses not at risk of alloimmune anemia between 13 and 37 weeks.

RESULTS

In control fetuses, PSV varied with gestation (PSV = 0.56 - 0.032 GA + 0.00086 GA2, where GA is gestational age; R2 = 0.41). The correlation between PSV and hematocrit Z scores (Pearson correlation coefficient r = -0.69) was highly significant (P = 0.0001). Using a PSV > 1 SD, the sensitivity of the test in predicting a fetal hematocrit < 2 SD below the mean was only 64% but the specificity was 100%. However, the sensitivity of the test in predicting a fetal hematocrit < 3 SD and < 4 SD rose to 73% and 83%, while the specificity was still good (93% and 80% respectively).

CONCLUSIONS

MCA PSV and fetal hematocrit are highly significantly correlated. The sensitivity of the test was good and the high positive predictive value indicates that the presence of a raised PSV (defined as > 1 SD) is a strong indicator of fetal anemia. In conclusion, MCA PSV is a useful test in clinical practice for the detection of fetal anemia.

Severe fetomaternal hemorrhage: a review

The etiology, clinical presentation, obstetrical antecedents, and outcome of pregnancies complicated by large fetomaternal hemorrhage (FMH) were reviewed by doing a MEDLINE search from 1966 to the present and manual search before 1966. One hundred thirty-four infants with FMH > 50 dl were reported in the literature. The primary variables: birth weight, gestational age, presence of sinusoidal fetal heart rate pattern, decrease or absent fetal body movements (FBM) estimated the amount of fetomaternal bleeding and the pretransfusion hemoglobin. Other variables included the condition of the infants at birth, erythroblasts, and reticulocyte blood counts at birth, as well as the year of publication. Thirty-five of the 134 cases were preterm. Twenty infants born to mothers reporting decreased or absent FBM survived. FBM was absent in 17 cases for a period ranging between 24 hours and 7 days. In this group, six infants survived, five were stillborn, and five died in the neonatal period. A sinusoidal heart rate (SHR) pattern was reported in 21 cases. A SHR pattern was associated with decreased FBM in 13 cases (39.3 percent). Fifteen cases with sinusoidal fetal heart rate pattern survived (71.4 percent). Both decreased or absent FBM and SHR patterns were reported more often in 1990 or later than before 1990 (P < .0017 and P < .008, respectively). The cause of FMH was not known in 82 percent of the cases. The most common presenting symptoms of FMH were anemia at birth (35.2 percent), decreased or absent FBM (26.8 percent), and unexpected stillbirths (12.5 percent). Seventeen intrauterine transfusions were performed in nine cases (eight survived). A negative correlation was found between pretransfusion hemoglobin and FMH (r = -0.35; P = .0019). No significant difference was found between the cases with FMH of > 200 ml or < 200 ml. Thus, decreased or absent FBM, SHR pattern, or hydrops fetalis are late signs of FMH. Other means of early detection are needed. The role of intrauterine transfusion (IUT) needs to be better defined. The inadequate outcome data indicate the need to follow infants born with large FMH into childhood to document the effect on the central nervous system.

Release of vasoactive agents during cordocentesis: differences between normally grown and growth-restricted fetuses

OBJECTIVE

The purpose of this study was to evaluate whether cordocentesis is associated with the release of vasoactive substances and whether there are differences between normally grown and growth-restricted fetuses.

STUDY DESIGN

6-Keto-prostaglandin F1 alpha (the stable metabolite of prostacyclin), endothelin-1, and cyclic guanosine monophosphate were measured in fetal blood at the beginning and closing of cordocentesis in 30 normally grown fetuses and 25 growth-restricted fetuses. This latter group was characterized by abnormal Doppler index values in umbilical artery and middle cerebral artery, suggestive of chronic hypoxemia as the causative factor of the impaired growth. In six growth-restricted fetuses bradycardia occurred at the end of the procedure. Umbilical artery pulsatility index was measured by Doppler ultrasonography immediately before and after the procedure.

RESULTS

The median interval between the two blood samples obtained by cordocentesis was 90 seconds (range 60 to 320 seconds). During this interval a significant rise of 6-keto-prostaglandin F1 alpha (p < or = 0.0001) and endothelin-1 (p = 0.03) was evidenced in normally grown fetuses. The increase in 6-keto-prostaglandin F1 alpha was significantly related (r = 0.52, p = 0.002) to the fall of umbilical artery pulsatility index occurring after the procedure. In growth-restricted fetuses cordocentesis induced a marked increase of endothelin-1 (p = 0.0002), which was significantly related to the severity of acidosis (r = 0.52, p = 0.018), whereas no modifications were evidenced for the other agents tested. The increase of endothelin-1 was higher in those growth-restricted fetuses showing bradycardia at the end of the procedure than in growth-restricted fetuses that did not (p = 0.04). The variations of the vasoactive substances assayed were not significantly related to the type of procedure (transamniotic or transplacental), the amount of blood aspirated during the procedure, the interval elapsing between the first and second samples, the gestational age at which the procedure was performed, and the degree of fetal smallness.

CONCLUSION

Cordocentesis induces the rapid release of vasoactive substances and the effect differs between normally grown and growth-restricted fetuses. This may explain the different hemodynamic response and the higher rate of complications occurring in the latter group after cordocentesis.

Middle cerebral artery flow velocity waveforms in normal and small-for-gestational-age fetuses

The middle cerebral artery flow velocity waveforms were obtained in 16 normal fetuses in a longitudinal study and in 128 normal fetuses in a cross-sectional study with pulsed Doppler ultrasonography. The pulsatility index values of the middle cerebral artery were higher at 25 to 30 weeks' gestation than those observed during the two periods of major cerebral cellular multiplication in the human fetus. In 9 of the 16 fetuses studied longitudinally we compared the pulsatility index values obtained at the end of gestation with those obtained at 1 month after delivery; no significant difference was observed. The pulsatility index of the middle cerebral artery was also determined in 33 small-for-gestational-age fetuses. A middle cerebral artery pulsatility index value below our normal range was recorded in 9 of the 33 small-for-gestational-age fetuses (27.3%). These small-for-gestational-age fetuses with abnormal pulsatility index values had a significantly higher incidence of abnormal fetal heart rate and admission into the neonatal intensive care unit. There were three deaths in the nine small-for-gestational-age fetuses with abnormal pulsatility index values (33.3%) and three deaths in the 24 small-for-gestational-age fetuses with normal pulsatility index values (12.5%). Our data indicate that the pulsatility index of the middle cerebral artery in the normal human fetus has a parabolic pattern during pregnancy and does not change significantly after delivery. The results suggest that the small-for-gestational-age fetus with a normal middle cerebral artery pulsatility index is at lower risk than the fetus with abnormal pulsatility index values; moreover, management of the small-for-gestational-age fetus may be aided by the study of the middle cerebral artery waveforms.

Arterial blood flow velocity waveforms of the pelvis and lower extremities in normal and growth-retarded fetuses

Serial measurements of femoral artery flow velocity waveforms were made at specified intervals of 3 to 4 weeks from 15 to 20 weeks of gestational age to 35 weeks and 1- to 3-week intervals thereafter until delivery in 12 normal fetuses (group 1A) with pulsed Doppler ultrasonography. The pulsatility index of the femoral artery increased linearly with advancing gestation in all 12 fetuses; this was associated with reverse diastolic flow velocity waveforms. In 30 other normal fetuses (group 1B) whose gestational ages ranged between 16 and 38 weeks (mean +/- SD, 29.5 +/- 5.6 weeks), the femoral artery flow velocity waveforms were analyzed with the external iliac artery, internal iliac artery, and umbilical artery waveforms. No significant difference was observed between the pulsatility index of the external iliac artery and that of the femoral artery (mean +/- SD, 3.7 +/- 1.1 vs 3.7 +/- 1.1). The pulsatility index of the internal iliac artery was significantly higher than that observed in the umbilical artery (mean +/- SD, 1.27 +/- 0.28 vs 1.12 +/- 0.23). The femoral and umbilical artery velocity waveforms also were determined in 20 fetuses with intrauterine growth retardation (group 2), whose gestational ages ranged between 24 and 36 weeks (mean +/- SD, 31 +/- 3.4 weeks). Abnormal femoral artery pulsatility index was recorded in two fetuses who died. Absent or reverse flow of the umbilical artery was recorded in 10 fetuses; four of them died, and four others manifested fetal distress or required admission to the neonatal intensive care unit or both. These preliminary data suggest that the femoral artery pulsatility index cannot be used as an indicator of adverse fetal outcome, whereas absent or reverse flow of the umbilical artery seems to be better correlated with adverse fetal outcome.