Umbilical Artery Blood Flow Velocity Research Articles

Antenatal fetal risk assessment using a neurofuzzy technique.

This study defines an intelligent neurofuzzy system for antepartum fetal evaluation, The task is to investigate the Doppler ultrasound measurements of the umbilical artery (UA) and the cerebral artery (CA) to relate the health conditions of fetuses. We thus use the UA blood flow velocity waveforms [pulsality index, resistance index, and systolic/diastolic ratio] and the ratios of cerebral-umbilical resistance indices in terms of weeks. We then make a decision on the basis of a fuzzy-rule-based system combined with data-based learning strategies such as a radial basis function network and a multilayer perceptron for assessing the hypoxia suspicion. A fuzzy grade of membership is used for the evaluation of the seriousness of the situation of the fetus, and the diagnostic interpretations for doctors such as good, suspicious, and alarming conditions of fetus are derived.

Contrast-Enhanced Ultrasonography of Uteroplacental Circulation Does Not Evoke Harmful CTG Changes or Perinatal Events

Objective: To determine whether an intravascular ultrasound contrast agent used in the examination of uteroplacental circulation in late pregnancy has any effect on fetal cardiotocographic (CTG) parameters or fetal well-being. Methods: The uteroplacental circulation of 69 women with singleton third trimester pregnancies was examined by power Doppler with contrast agent (Levovist^®; Schering AG, Berlin, Germany) enhancement. Computed CTG examination using Dawes/Redman criteria was recorded just before and after ultrasonographic examination in 25 subjects examined with contrast agent and in 15 control patients who were given only physiological saline injection during ultrasonography. Umbilical artery blood flow velocity waveform was examined in 15 subjects before and 5 min after maternal contrast agent injection. Obstetric outcome of all the 69 subjects was evaluated by birthweight, placental weight, fetal and neonatal distress, prenatal hemorrhages, cord arterial and venous blood pH and macroscopic placental examination. Results: No apparent fetal or maternal harmful effects caused by the contrast-enhanced ultrasonography were observed. In CTG examination there was a statistically significant increase in the number of accelerations and fetal movements and in short-term variation after administration of the contrast agent in both subjects and controls. There were no significant changes in the umbilical artery blood flow velocity waveform after administration of the contrast agent. Conclusions: Contrast agent enhancement in the examination of uteroplacental circulation does not produce any harmful fetal or placental effects in late pregnancy. Ultrasonographic examination itself, obviously due to maternal stress reaction, is associated with a slight activation of fetal behavioral status.

Umbilical artery blood flow velocity in pregnancies complicated by systemic lupus erythematosus.

We evaluated the role of umbilical artery Doppler velocimetry in the surveillance of pregnancies complicated by systemic lupus erythematosus (SLE). We retrospectively studied 56 women with SLE whose pregnancies were managed at our perinatal center between 1988 and 1995. Absent or reversed end-diastolic flow velocity was detected in 6 (11%) of 56 patients. This sub-group of patients had an increased risk of pre-eclampsia, intrauterine growth restriction, cesarean section, and preterm delivery. A high incidence (11%) of abnormal umbilical artery waveforms was detected. This finding was associated with an increased risk of maternal and fetal complications.

Umbilical artery catheters and blood flow velocities in the superior mesenteric artery: effect of insertion, removal, aspiration, and bolus infusion.

We studied whether umbilical artery catheters (UACs) affect blood flow in the superior mesenteric artery (SMA) of neonates. Noninvasive duplex pulsed Doppler sonography was used to measure peak systolic velocity, end-diastolic velocity, and mean flow velocity in the SMA. The resistance index and pulsatility index were calculated from these data. Thirty-two infants weighing 450-2,520 g at birth were enrolled in the study. Gestational age at birth was 24-37 weeks. Eighteen infants were studied before and after UAC insertion. Twenty infants were studied before and after UAC removal. Eleven infants with UACs were studied before and during aspiration of blood from the UAC and during bolus infusion of 5% dextrose solution into the UAC. Data were compared before and after UAC insertion; before and after UAC removal; and before and during aspiration and during bolus infusion. Blood flow velocities and vascular resistance were similar in all comparisons except for increases in end-diastolic and mean velocities after UAC insertion. Insertion and removal of UACs, aspiration of blood from UACs, and bolus infusion of fluids into UACs do not diminish blood flow velocity or increase vascular resistance in the SMA.

Feature discovery and classification of Doppler umbilical artery blood flow velocity waveforms

Doppler umbilical artery blood flow velocity waveform measurements are used in perinatal surveillance for the evaluation of fetal condition. There is an ongoing debate on the predictive value of Doppler measurements concerning the critical effect of the selection of parameters for the interpretation of Doppler waveforms. In this paper, we describe how neural network methods can be used both to discover relevant classification features and subsequently to classify Doppler umbilical artery blood flow velocity waveforms. Results obtained from 199 normal and high risk patients' umbilical artery waveforms highlighted a classification concordance varying from 90 to 98% accuracy.

The effect of isosorbide dinitrate on uterine artery and umbilical artery flow velocity waveforms at mid-pregnancy

To study the effect of isosorbide dinitrate, a nitric oxide donor, on the maternal cardiovascular system and on uterine and umbilical artery blood flow velocities in mid-pregnancy. Eighteen women with low-risk pregnancy at 17-24 weeks' gestation were given a single 5-mg dose of sublingual isosorbide dinitrate, a nitrovasodilator. Blood flow velocity waveforms in the ascending uterine artery and in the umbilical artery were measured by an image-directed, pulsed color Doppler ultrasound scan before and after the medication was administered. Maternal blood pressure (BP) and heart rate were also obtained. The mean arterial BP decreased from 86 mmHg (95% confidence interval [CI] 72-99) to a nadir of 73 mmHg at 6 minutes (95% CI 61-85, P < .04). Mean maternal heart rate increased from 85 beats per minute (95% CI 80-90) to 96 beats per minute at 6 minutes (95% CI 87-105, P < .01). Mean systolic-diastolic flow velocity ratio (S/D) in the umbilical artery rapidly declined from 4.18 (95% CI 3.80-4.56), reaching a nadir of 3.12 at 6 minutes (95% CI 2.65-3.84, P < .001). The S/D in the uterine artery decreased from 4.83 (95% CI 3.99-5.56) to a nadir of 4.02 at 10 minutes (95% CI 3.41-4.63, P < .001). Isosorbide dinitrate, a donor of nitric acid, lowers mean maternal BP and reduces the Doppler impedance in the umbilical and uterine arteries. This drug could prove to be beneficial when endothelial cell dysfunction leads to insufficient synthesis and release of endothelium-derived relaxing factor, resulting in generalized vasoconstriction and increased resistance to flow in the uteroplacental circulation.

A computerized diagnostic system for the interpretation of umbilical artery blood flow velocity waveforms

Objective: Development of an artificial intelligent diagnostic system for the interpretation of umbilical artery blood flow velocity waveform measurements. Study design: Study design comprised several stages including data acquisition, image processing and analysis, training of artificial neural network and testing the predictive value of the system. The clinical material was handled in two groups. The training group consisted of 952 umbilical artery blood flow velocity waveform images of 174 normal pregnancies with normal outcome, while the testing group was composed of 138 images derived from 20 normal pregnancies with normal outcome and 68 images of 16 high risk pregnancies with poor outcome. All subjects were evaluated by Doppler ultrasonography and umbilical artery blood flow velocity waveform images were transferred to the computer environment by means of a special data acquisition system. Automated image processing and analysis were performed to derive indices such as A/B ratio, resistance index, pulse related index, area ratio of wave and angle of coincident slopes. We have used a supervised artificial neural network (back propagation learning algorithm) to develop an intelligent diagnostic system which is called the BOLU system. Results: This version of the system was trained with the umbilical artery blood flow velocity waveform images of normal pregnancies. Thus, the BOLU system decides whether the tested image is normal for a given gestational week or not. The specificity and sensitivity of this system were estimated to be 98.6% and 51.5% respectively. Conclusion: We have developed an artificial intelligent diagnostic system for the interpretation of umbilical artery blood flow velocity waveform measurements. Waveform indices were obtained automatically by image processing and analysis. The predictive value of the system was found to be satisfactory.

Elevated serum group II phospholipase A2 levels are associated with decreased blood flow velocity in the umbilical artery.

Twenty-two hospitalized patients, diagnosed as having hypertensive disorder of pregnancy, were selected from two University Clinics. Maternal serum samples were analyzed for serum group II phospholipase A2 (PLA2-II) by time-resolved fluoroimmunoassay. At the same time, umbilical artery blood flow velocities were measured with color Doppler sonography for orientation and pulsatile Doppler sonography for recording waveforms. Nineteen normotensive third-trimester pregnant patients served as a control group. Maternal serum PLA2-II was elevated in 8 cases with preeclampsia. This elevation was invariably associated with decreased blood flow velocity in the umbilical artery. In 1 case, the clinical condition allowed simultaneous follow-up of serum enzyme and blood flow velocity: a further rise of serum PLA2-II was linked to a further decrease in the blood flow velocity of the umbilical artery. A large spillover of the elevated PLA2-II content from the preeclamptic placenta into the maternal serum is associated with a decrease in blood flow velocity in the umbilical artery. The enzyme might serve as a link between local proximal (placenta) and systemic distal (umbilical arterial blood flow) effectors.

Reduced placental villous tree elaboration in small-for-gestational-age pregnancies: Relationship with umbilical artery Doppler waveforms

Our purpose was to investigate the three-dimensional architecture of placental villi from normal and growth-restricted fetuses and relate findings to umbilical artery blood flow velocity waveforms. Placentas from term (n = 15) and preterm (n = 5) appropriately grown and term (n = 9) and preterm (n = 7) growth-restricted fetuses (birth weight < 10th percentile) were examined to determine the number of arteries per stem villus and the three-dimensional configuration of the villous trees and their vessels. Umbilical blood flow before delivery was assessed by Doppler ultrasonography. The effects of age and growth restriction were determined by two-way analyses of variance. Growth restriction was associated with reduced large vessel wall thickness (p < or = 0.05) but no reduction in the number of these vessels per stem villus. The volumes and surface areas of intermediate and terminal villi were reduced (p < or = 0.001), especially in preterm growth-restricted cases, where a marked reduction in diastolic blood flow velocity was observed in the umbilical artery. Reduced villous development may contribute to abnormal umbilical artery blood flood flow, as assessed by Doppler ultrasonography, in some cases of intrauterine growth restriction.

Epidural anaesthesia for elective Caesarean section does not influence fetal umbilical artery blood flow indices

This prospective study was completed to determine the influence of epidural anaesthesia on the fetoplacental circulation of normal subjects. Thirty-seven normal pregnant patients at term, undergoing elective Caesarean section, had Doppler measurements of the fetal umbilical artery blood flow velocity before and after epidural anaesthesia using lidocaine 2% without epinephrine. There were no differences in systolic/diastolic, resistance or pulsality indices following epidural anaesthesia. These results suggest that this technique has no adverse effect on fetoplacental circulation in normal non-labouring subjects.

CK-BB as indicator of prenatal brain-cell injury in fetuses with absent or reverse end-diastolic flow velocities of the umbilical arteries

The purpose of this study is to determine the levels of brain type isoenzyme of creatine kinase (CK-BB) as a possible indicator of a pre-existing intrauterine brain-cell damage in cord blood sera of fetuses with preceding absent or reverse end-diastolic flow velocities of the umbilical arteries (AREDFV). CK-BB isoenzyme activities were determined in umbilical cord sera of 13 newborn infants with preceding AREDFV and in 14 fetuses with low end-diastolic flow velocities (LEDFV) of the umbilical arteries. 50 newborn infants with elective cesarean section and normal umbilical artery blood flow velocity waveforms were used as controls. Two-tailed Student's t-test and Fischer's exact test were used for statistical evaluation of the results. CK-BB isoenzyme activity did not depend on gestational age. Fetuses with AREDFV showed a significant increase in CK-BB values, whereas fetuses with LEDFV had CK-BB activities within the normal range of the controls. The elevated CK-BB values of the AREDFV group were not correlated with fetal acidosis at birth. Brain-cell injury with leakage of CK-BB isoenzyme might be present in fetuses with AREDFV even before (preterm) delivery.

The effect of cordocentesis on umbilical and middle cerebral artery blood flow velocity waveforms.

To investigate the effect of cordocentesis on the umbilical and fetal cerebral circulation. Cross sectional study. Department of Obstetrics and Gynaecology, Regional Referral Centre for Fetal Medicine, Klagenfurt Hospital, Austria. Thirty pregnant women undergoing diagnostic cordocentesis at 18 to 38 weeks' gestation. The pulsatility index (PI) in the umbilical artery and fetal middle cerebral artery was measured by pulsed Doppler ultrasound before and immediately after cordocentesis. Change in umbilical artery PI and middle cerebral artery PI. Cordocentesis was associated with a significant decrease in both umbilical artery PI (median -0.18, range -2.21 to 1.5, P < 0.004) and middle cerebral artery PI (mean -0.15, SD 0.32, P < 0.03) and the decrease in umbilical artery PI was most marked when cordocentesis was performed transplacentally. In four cases, there were absent or reversed frequencies at the end of diastole (EDF) in the umbilical artery before cordocentesis, and in all cases there were positive EDF after the procedure. In contrast, one of the 26 cases with positive EDF developed reversed EDF following the procedure. Acute alterations in the waveforms from both the umbilical and fetal cerebral circulation can be induced by cordocentesis. The decrease in resistance in the fetoplacental circulation could be attributed to the release of vasodilators, and the increase in resistance observed in some cases could be secondary to arterial vasospasm. Better understanding of the underlying mechanisms might help in making cordocentesis a safer procedure.

Umbilical artery and ductal blood flow velocities in patients treated with aspirin and prednisone for presence of anticardiolipin antibody

Fifteen patients with previous pregnancy losses and positive plasma anticardiolipin antibody (ACA) were treated with prednisone (15 mg/day) and aspirin (80 mg/day). We measured Doppler velocimetries of umbilical artery and ductus arteriosus at intervals of 2 to 3 weeks starting from 20 weeks of gestation until delivery. Umbilical artery systolic/diastolic ratios (S/D) and maximum systolic velocities of ductus arteriosus did not differ from normal values. There were no poor outcomes in the treated group. ACA positive patients with previous poor pregnancy outcome when treated with prednisone and aspirin have umbilical artery and ductal flow velocities similar to those of the normal population.

Response of Blood Flow Velocity Waveforms in the Abdominal Aorta and Cotyledonary Artery to Regional Embolization of the Umbilical Circulation in Fetal Sheep

Regional embolization of the placental circulation was performed in 3 anesthetized fetal sheep by retrograde administration of microspheres in a cotyledonary branch of one of the umbilical arteries. Registrations were made of blood velocity waveforms in the fetal abdominal aorta and in a major cotyledonary artery supplying the embolized placental region. Among the fetal lambs examined, a corresponding degree of regression was found between the decrease in umbilical blood flow and increase in the pulsatility index of the abdominal aorta waveforms (coefficient of variation: 0.19). In contrast, the degree of regression between the decrease in umbilical blood flow and increase in the pulsatility index of the cotyledonary artery waveforms varied per fetus (coefficient of variation: 0.79). It is suggested that in human fetuses, in the case of discordant umbilical artery blood flow velocity waveforms, the best information on fetoplacental circulatory competence is provided by the aorta blood velocity waveform.

The Effect of Maternal Hypoxemia on the Umbilical and Femoral Artery Blood Flow Velocity Waveforms and the Relationship with Mean Arterial Pressure in Fetal Sheep

The relationship between the ratio femoral pulsatility index (PI)/umbilical PI and arterial oxygen content was examined in 8 fetal sheep at various stages of hypoxemia. This relationship was characterized by an inconsistent increase of the ratio femoral PI/umbilical PI at oxygen content levels beneath 1.0 mM. The correlation coefficient of the linear regression between both variables was only -0.54, indicating that prediction of fetal oxygenation on the basis of Doppler waveform measurements in peripheral fetal arteries might be invalid. The average correlation coefficient of the linear regressions between the femoral PI and fetal mean arterial pressure was 0.87 +/- 0.15 (SD), whereas the average correlation between the umbilical PI and fetal mean arterial pressure was 0.04 +/- 0.61. These data suggest that the degree of change in fetal mean arterial pressure considerably depends on the degree of change in vascular resistance in the fetal carcass.

Short-term effects of ritodrine, aminophylline and atropine on umbilical artery blood flow velocity waveform

With the recent introduction of Doppler technology, a non-invasive methodology which enables to evaluate qualitative changes in circulatory vessels, it is possible to investigate the possible effects of various drugs on several parameters of utero-placental-fetal circulation. In the present study we evaluate the flow velocity waveform (FVW) of umbilical artery (UA) during and after administration of aminophylline, atropine and ritodrine to healthy pregnant women. In our study we did not observe any significant short-term variation of PI after the administration of these drugs. Slight variations were detected, and they may be interpreted on the basis of the mode of action of these drugs. Doppler technology may be a useful tool for monitoring some effects on the fetus of the maternal administration of therapeutic agents.

Umbilical artery blood flow velocity waveforms in twin pregnancies.

To detect discordant fetal growth in twin pregnancies and assess a possible role for Doppler ultrasound measurements of blood flow velocity waveforms in umbilical arteries in such cases, 32 twin pregnancies were examined on 125 occasions. The last examination was within 14 days of delivery. There was postpartum death of one pair of twins with the twin transfusion syndrome. Birthweight was appropriate for gestational age in 15 twin pairs, both infants were small for gestational age (SGA) in 5, and one of the infants was SGA in 12 twin pairs. The correlation coefficient of RI difference at the last examination and percentage birth weight difference in twin pairs was 0.68. Cutoff points for the delta RI and weight difference were established. The sensitivity of delta RI (0.1) was 77.8%; specificity, 95.8%; positive predictive value, 87.5%; and negative predictive value, 92.0%.

Predictive value of uterine artery velocity waveforms in pregnancies complicated by systemic lupus erythematosus and the antiphospholipid syndrome.

The objective of this study was to see if determination of uterine artery velocity waveforms between 20 and 30 weeks in lupus pregnancy and the antiphospholipid syndrome (APS) have a good predictive value for later fetal distress before labor, intrauterine growth retardation, and preeclampsia. Uterine and umbilical artery blood flow velocity waveforms were determined in 21 pregnancies complicated by systemic lupus erythematosus (SLE): 12 with antiphospholipid antibodies (aPL), 9 without aPL. We also studied 7 pregnancies with APS. This retrospective study was running from January 1st 1986 to July 31st 1991, at the Port-Royal Maternity, Paris, France. Abnormal uterine artery blood flow velocity waveforms were found in 10 out of 28 pregnancies at the first examination performed between 20 and 30 weeks gestational age. All the later adverse fetal and neonatal events were predicted by an abnormal uterine artery blood flow velocity waveform. From the 7 cases of fetal distress diagnosed during pregnancy, 6 were predicted by abnormal uterine waveforms and all of these pregnancies resulted in induced delivery before 32 weeks of gestational age. Twelve pregnancies with aPL and normal uterine artery waveforms were uncomplicated. Only 1 out of 7 pregnancies with abnormal uterine artery waveform and aPL ended without complication. Determination of uterine artery flow velocity waveform is a good adjunct to the management of pregnancies complicated by SLE or aPL. This determination has a better predictive value than the presence of aPL.

Oral Isradipine and Feto-Maternal Hemodynamics in Hypertensive Pregnancy

The effect of the calcium channel blocker, isradipine, on blood pressure and on uteroplacental and fetal blood flow was investigated in 27 patients with hypertension in pregnancy, before and after one week's treatment with 2.5 - 5.0 mg b.i.d. of the drug. In addition 21 hypertensive pregnant women without pharmacological treatment were investigated twice with a one week interval with regard to the same hemodynamic variables. Uteroplacental blood flow was investigated with dynamic placental scintigraphy. The uterine artery, the umbilical artery and fetal thoracic aortic blood flow velocity was measured by spectral doppler ultrasound. In the untreated group the blood pressure remained constant, and there were neither any changes in the uteroplacental or fetal blood flow vartiables. In the isradipine group there was a significant reduction in mean arterial blood pressure from 117 rnmHg to 112 mmHg (p<0.001). Treatment with isradipine did not affect the uteroplacental blood flow or the maternal and fetal bloo...

Umbilical artery blood flow velocity waveforms in pregnancy complicated by diabetes mellitus

Umbilical artery blood velocity waveforms were recorded by a pulsed Doppler system in the third trimester of pregnancy in 16 diabetic women (12 class B, 1 class C, 3 class D) and the waveforms were analysed for resistance index (RI = peak systolic velocity minus end diastolic velocity/peak systolic velocity). There was no significant correlation between the RI values and either serum glucose (r = 0.385) or fructosamine levels (r = 0.380). However, the RI values were raised in two cases with serum glucose levels of over 300 mg/dl. With a fall in serum glucose levels, the RI values returned to the normal range. No abnormal umbilical artery velocity waveforms were found when the serum glucose level was below 200 mg/dl.