Umbilical Artery Blood Flow Velocity Research Articles

The value of middle cerebral artery to umbilical artery ratio by Doppler velocimetry in low risk postdate pregnancies

Background and objective: Placental insufficiency is the primary cause of intrauterine growth restriction in normally formed fetuses and can be identified using middle cerebral artery to umbilical artery ratio Doppler velocimetry, and provide an estimate of downstream placental vascular resistance and placental blood flow. There is a strong association between reduced end-diastolic umbilical artery blood flow velocity and increased vascular resistance in umbilical placental microcirculation. Doppler ultrasound can assess the uteroplacental blood flow just before labor. This study aimed to investigate the use of the fetal cerebroumbilical ratio to predict the intrapartum fetal compromise in appropriately grown fetuses. Methods: A comparative cross-sectional study set at Sulaimania Maternity Teaching Hospital, Sulaimania, Iraq, from January to June 2015. The study recruited 121 cases, fetal biometry and Doppler indices were measured before established labor. The intrapartum and neonatal outcome details recorded. Results: Infants delivered by cesarean section for fetal compromise had significantly lower cerebroumbilical ratio than those born by spontaneous normal (none assisted) vaginal delivery and by cesarean section for other intrapartum causes. Infants with cerebroumbilical ratio 10th percentile. A cerebroumbilical ratio >90th percentile appears protective against cesarean section for fetal compromise. Amniotic fluid index of < 5 was associated with an increased cesarean section for fetal indication. Conclusion The cerebroumbilical ratio can identify fetuses at high risk of intrapartum fetal compromise. As a confounding variable, the amniotic fluid index was a useful tool for surveillance in prolonged pregnancy.

Doppler Audio Signal Analysis as an Additional Tool in Evaluation of Umbilical Artery Circulation

Purpose To investigate the predictive capacity of a new method for sound spectrum analysis of Doppler signals recorded from the umbilical artery in high-risk pregnancies. Material and Methods The retrospective study comprised 127 pregnant women with various pregnancy complications between 23 and 39 gestational weeks. Umbilical artery blood flow velocity waveforms were recorded with Doppler ultrasound and characterized by pulsatility index (PI) and blood flow class (BFC). Doppler audio signals were stored on a digital video recorder and the sound frequency at the energy level 15 dB below its peak (MAXpeak-15 dB) was estimated off-line. The prediction of probability for composite adverse pregnancy outcome (operative delivery for fetal distress, admission to neonatal intensive care unit, perinatal death) was evaluated using the area under the curve (AUC) of the receiver operating characteristics (ROC) curve. Results With increasing umbilical artery BFC, the MAXpeak-15 dB frequencies decreased (p < 0.0001) and the PI increased (p < 0.0001). The ROC AUCs for adverse outcome for MAXpeak-15 dB and for PI were 0.842 and 0.836 (p = 0.88), respectively. For the combination of MAXpeak-15 dB and PI, the corresponding AUC was 0.894, significantly higher than that of PI (p < 0.03) and of MAXpeak-15 dB (p < 0.05). Conclusion Umbilical artery Doppler sound spectrum analysis might be a useful supplement to PI in the clinical evaluation of fetoplacental circulation.

Sildenafil Citrate Increases Fetal Weight in a Mouse Model of Fetal Growth Restriction with a Normal Vascular Phenotype

Fetal growth restriction (FGR) is defined as the inability of a fetus to achieve its genetic growth potential and is associated with a significantly increased risk of morbidity and mortality. Clinically, FGR is diagnosed as a fetus falling below the 5th centile of customised growth charts. Sildenafil citrate (SC, Viagra™), a potent and selective phosphodiesterase-5 inhibitor, corrects ex vivo placental vascular dysfunction in FGR, demonstrating potential as a therapy for this condition. However, many FGR cases present without an abnormal vascular phenotype, as assessed by Doppler measures of uterine/umbilical artery blood flow velocity. Thus, we hypothesized that SC would not increase fetal growth in a mouse model of FGR, the placental-specific Igf2 knockout mouse, which has altered placental exchange capacity but normal placental blood flow. Fetal weights were increased (by 8%) in P0 mice following maternal SC treatment (0.4 mg/ml) via drinking water. There was also a trend towards increased placental weight in treated P0 mice (P = 0.056). Additionally, 75% of the P0 fetal weights were below the 5th centile, the criterion used to define human FGR, of the non-treated WT fetal weights; this was reduced to 51% when dams were treated with SC. Umbilical artery and vein blood flow velocity measures confirmed the lack of an abnormal vascular phenotype in the P0 mouse; and were unaffected by SC treatment. 14C-methylaminoisobutyric acid transfer (measured to assess effects on placental nutrient transporter activity) per g placenta was unaffected by SC, versus untreated, though total transfer was increased, commensurate with the trend towards larger placentas in this group. These data suggest that SC may improve fetal growth even in the absence of an abnormal placental blood flow, potentially affording use in multiple sub-populations of individuals presenting with FGR.

Observation on monitoring fetal umbilical blood flow in predicting fetal hypoxia and fetal prognosis

Objective To monitor fetal umbilical artery blood flow velocity and resistance,predicting fetal hypoxia and fetal prognosis.Methods 300 pregnant women were randomly selected,with 150 cases of abnormal pregnancy as the experimental group,and 150 cases of normal as the control group,color Doppler ultrasound was used in monitoring umbihcal artery resistance index and fetal hypoxia and fetal prognosis were observed.Results Abnormal hemodynamic indicators found in experimental group and the normal in control group.Of the experimental group,67 patients had intrauterine hypoxia,16 patients in control group had intrauterine hypoxia,with the proportion of 44.7％ and 10.7％,resulting in a significant difference (P＜0.01).Fetal malformations,intrauterine growth (IUGR),fetal distress and the proportion of poor prognosis in the experimental group were higher,showing a result of a significant difference (P＜0.01).Conclusions Prenatal monitoring fetal umbilical blood flow parameters indicators can effectively prevent fetal hypoxia and poor prognosis,improve neonatal quality. Key words: Umbilical blood flow; Fetal hypoxia; Color Doppler ultrasound

Metastin levels in pregnancies complicated by pre-eclampsia and their relation with disease severity

Aims: To evaluate the role of metastin levels in the pathophysiology of pre-eclampsia and to determine whether there is a relationship between the severity of the disease and Doppler velocimetry measurements. Methods: This cross-sectional study included 89 pregnant women (50 healthy normotensive pregnant women, 15 patients with mild pre-eclampsia, and 24 patients with severe pre-eclampsia) at the third trimester of pregnancy. The maternal levels of plasma metastin were determined by enzyme-linked immunosorbent assay. The umbilical artery and uterine artery blood flow velocities were measured by transabdominal color and pulsed Doppler ultrasound. Results: Plasma metastin levels were lower in patients with pre-eclampsia than those in the normotensive pregnant women. Four patients with mild pre-eclampsia and seven patients with severe pre-eclampsia had abnormal Doppler velocimetry findings. Metastin levels of pre-eclamptic patients with abnormal Doppler velocimetry findings were significantly lower than those in patients with normal Doppler velocimetry findings. Plasma metastin levels negatively correlated with proteinuria in 24 hours and with mean arterial pressure in the cases of pre-eclampsia. Conclusions: The findings suggest that decreased maternal concentrations of plasma metastin may be involved in the pathogenesis of pre-eclampsia. Plasma metastin levels may be useful in the assessment of the severity of pre-eclampsia. However, further trials are needed to clarify the role of metastin in pre-eclampsia.

Ultrasonography and Doppler studies in twin-to-twin transfusion syndrome.

In 40 twin pregnancies, the evaluation of hemodynamics by ultrasound was performed during the period January 1986 through September 1991. The blood flow velocities' waveforms in the umbilical artery, umbilical vein and tricuspid valve, and the total cardiac dimension, were obtained by ultrasonography in conjunction with 3.5 MHz pulsed Doppler ultrasound. Six patients with twin pregnancies were identified as having twin-to-twin transfusion syndrome (TTS), on the basis of like-sex twins with monochorionic diamniotic placentation, vascular anastomosis in the placenta, and umbilical cord venous blood hemoglobin difference exceeding 5 g/dl at delivery. No distinctive findings for TTS were revealed by the measurement of umbilical artery blood flow velocity waveforms. However, cardiomegaly in 5 recipient fetuses and tricuspid regurgitation and biphasic umbilical vein waveforms in 3 recipient fetuses constituted characteristic features of TTS. Ultrasonography and a Doppler study might be beneficial in diagnosing TTS and evaluating the hemodynamics in a recipient fetus.

A Modification of the Uterine Artery Restriction Technique in the Guinea Pig Fetus Produces Asymmetrical Ultrasound Growth

Aims To evaluate the use of diathermy ablation of branches of the uterine artery to produce growth restriction in the fetal guinea pig, and to compare this new approach with the more conventional use of uterine artery ligation. The development of growth restriction was documented by measuring fetal biparietal diameter (BPD) and the resistance index (RI) of the umbilical artery blood flow velocity waveform. Methods At 30–35 days of gestation (term = 70 days), one uterine artery was ligated in 29 sows. In another 16 sows, branches of one uterine artery were ablated using diathermy. Fetuses in contralateral horns were used as controls. Ultrasound measurements were made weekly, and at 59–69 days of gestation animals were euthanased to determine fetal position in utero as well as fetal and placental weights. In some fetuses, brain and liver weights were also recorded. Results Both surgical techniques resulted in similar reductions in fetal body and placental weights. The number of fetuses surviving to term was greater in the diathermy group (53%) compared to the ligation group (22%) ( P < 0.05). Results from these two groups were combined and referred to as “treated” fetuses. The brain/liver weight ratio was increased by 245% in the treated fetuses compared to control fetuses. Ultrasound measures of BPD in the treated fetuses were within the normal range. The mean RI of the treated group showed a slight but significant increase near term compared to the mean RI of the normal range. Conclusion We have shown that the diathermy technique produces asymmetrical fetal growth restriction (with normal head size) in the guinea pig to the same extent as the conventional ligation technique. It is associated with a lower fetal mortality rate and therefore should be the preferred method. The minimal increase in umbilical artery resistance index only at the end of gestation amongst the intrauterine growth restriction (IUGR) fetuses suggests that an obliterative vasculopathy in the umbilical circulation is not the cause of growth failure when there is maternal uteroplacental restriction.

829: Temporal changes in fetal heart rate patterns—a new dimension in fetal assessment

To compare temporal changes (trends) in computed FHR parameters obtained by numerical analysis of repeated non-stress tests between normal pregnancies and pregnancies with an abnormal biophysical profile or an increase in the resistance to flow in umbilical artery blood flow velocity waveforms (FVW's).

P46.07: Perinatal outcome according to umbilical artery blood flow velocity waveform of term pregnancies with small for gestational age pregnancies

P46.07: Perinatal outcome according to umbilical artery blood flow velocity waveform of term pregnancies with small for gestational age pregnancies

Middle cerebral artery blood flow velocities and pulsatility index and the cerebroplacental pulsatility ratio: longitudinal reference ranges and terms for serial measurements

To establish reference ranges suitable for serial assessments of the fetal middle cerebral (MCA) and umbilical (UA) artery blood flow velocities, pulsatility index (PI) and cerebroplacental pulsatility ratio and to provide terms for calculating conditional reference intervals suitable for individual serial measurements. This was a longitudinal study of 161 singleton pregnancies. Using Doppler ultrasound, MCA and UA blood velocities and PI were determined three to five times at 3-5-week intervals over a gestational age range of 19-41 weeks. Polynomial regression lines for the 95th, 50th and 5th percentiles were calculated for the peak systolic velocity (PSV), time-averaged maximum velocity (TAMXV), PI and cerebroplacental ratio. Terms for calculating conditional reference intervals were established. Based on 566 observations our new longitudinal reference ranges for fetal middle cerebral PSV, TAMXV and PI provided terms for calculating conditional reference intervals (i.e. predicting expected 95% confidence limits based on a previous measurement), and correspondingly for the cerebroplacental ratio (n = 550). The reference ranges were at some variance with those of previous cross-sectional studies. The narrow 95% confidence limits for the 5(th) and 95(th) percentiles ensured reliable ranges. We have established longitudinal reference ranges appropriate for the serial assessment of MCA blood velocities and PI and cerebroplacental ratio. Particularly the terms for calculating conditional ranges based on a previous observation make this system more appropriate for longitudinal monitoring than are cross-sectional data.

Increased expression of N-myc downstream-regulated gene 1 (NDRG1) in placentas from pregnancies complicated by intrauterine growth restriction or preeclampsia

N-myc downstream-regulated gene 1 (NDRG1) modulates placental response to hypoxia. We therefore hypothesized that the expression of NDRG1 is altered in placentas from pregnancies complicated by intrauterine growth restriction (IUGR) or preeclampsia (PE), which are associated with fetoplacental underperfusion and cellular hypoxia. Thirty-five pregnant women in the third trimester of pregnancy were recruited according to the following 3 groups: (1) normal term pregnancy (n = 10), (2) pregnancy complicated by IUGR (n = 9), and (3) pregnancy with severe PE (n = 16). Placental samples were collected after cesarean delivery without labor. NDRG1 was measured with the use of immunostaining, Western blot, and real-time quantitative polymerase chain reaction (RT-qPCR). Umbilical artery blood flow velocity waveforms were recorded by Doppler ultrasound in women with IUGR and PE. By using immunostaining, we found a predominant expression of NDRG1 in the cytoplasm of villous trophoblasts. The expression of NDRG1 in samples from PE or IUGR was higher than control, with highest expression in PE. We confirmed these results by using immunoblotting and RT-qPCR. There was no correlation between the level of NDRG1 and umbilical artery blood flow. The expression of NDRG1 is upregulated in placentas from pregnancies complicated by severe PE or IUGR. This finding likely reflects trophoblast response to hypoxic injury.

Placental Doppler velocimetry in gestational diabetes mellitus

To evaluate if maternal glucose level and growth of the fetus were related to placental vascular impedance in pregnancy complicated by gestational diabetes mellitus. A retrospective study of 146 gestational diabetic women of which 117 needed insulin therapy. Glycosylated hemoglobin (HbA1c) was evaluated as well as umbilical and uterine artery Doppler velocimetry. The results were related to adverse outcome of pregnancy including newborn birthweight. Abnormal umbilical artery blood flow velocity was seen in 5% of the cases and abnormal uterine artery flow in 16%. Uterine and umbilical artery vascular impedance was significantly lower in macrosomic newborns. There was a poor correlation between HbA1c, vascular impedance and birthweight. There were 11 cases that developed preeclampsia, all having abnormal uterine artery Doppler and two abnormal umbilical artery Doppler. Uterine and umbilical artery vascular impedance in pregnancies complicated by gestational diabetes is related to birthweight and placental weight, but not to maternal HbA1c levels. Placental Doppler ultrasound does not seem to be of clinical value for fetal surveillance in these pregnancies unless the pregnancy is complicated by preeclampsia and/or intrauterine fetal growth restriction.

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

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

1166C mutation of angiotensin II type 1 receptor gene is correlated with umbilical blood flow velocimetry in women with preeclampsia

Objective. To ascertain the frequency of polymorphic variants of the gene coding for angiotensin II type 1 receptor (AT1) and its correlation with umbilical artery (UA) blood flow velocity in a group of women with preeclampsia (PE).Study design. AT1 polymorphism, pulsatility index (PI) in UA, and perinatal outcome in 47 women with PE and in 113 healthy pregnant women were investigated. Investigation of AT1 receptor genotypes was performed by PCR/RFLP assays. PI value has been measured by Doppler velocimetry technique.Results. The overrepresentation of CC?homozygotic genotype in PE group (6.4% vs. 2.7%) and the overrepresentation of mutated C allele in the PE group were observed (28.7% vs. 23.0%). Analyzing PI index we observed statistically significant differences between PE and control groups. Comparing PI values in PE group between genotypes: AA vs. AC + CC statistically significant differences (p?<?0.05) have been observed.Conclusions. Observed overrepresentation of mutated C allele of the AT1 gene was correlated with increased blood flow in umbilical artery in women with preeclampsia. Doppler velocimetry might be a useful tool for indication in the high-risk group with overrepresentation of C alleles.

1166C mutation of angiotensin II type 1 receptor gene is correlated with umbilical blood flow velocimetry in women with preeclampsia

To ascertain the frequency of polymorphic variants of the gene coding for angiotensin II type 1 receptor (AT1) and its correlation with umbilical artery (UA) blood flow velocity in a group of women with preeclampsia (PE). AT1 polymorphism, pulsatility index (PI) in UA, and perinatal outcome in 47 women with PE and in 113 healthy pregnant women were investigated. Investigation of AT1 receptor genotypes was performed by PCR/RFLP assays. PI value has been measured by Doppler velocimetry technique. The overrepresentation of CC homozygotic genotype in PE group (6.4% vs. 2.7%) and the overrepresentation of mutated C allele in the PE group were observed (28.7% vs. 23.0%). Analyzing PI index we observed statistically significant differences between PE and control groups. Comparing PI values in PE group between genotypes: AA vs. AC + CC statistically significant differences (p < 0.05) have been observed. Observed overrepresentation of mutated C allele of the AT1 gene was correlated with increased blood flow in umbilical artery in women with preeclampsia. Doppler velocimetry might be a useful tool for indication in the high-risk group with overrepresentation of C alleles.

Application of FFT-Analyzed Umbilical Artery Doppler Signals to Fuzzy Algorithm

Doppler signals, recorded from the umbilical artery of 60 women with pregnancy, were transferred to personal computer via a 16-bit sound card. The fast Fourier transform (FFT) method was applied to the recorded signal from each patient. Because FFT method inherently cannot offer a good spectral resolution at highly turbulent blood flows, it sometimes causes wrong interpretation of Doppler signals. In order to avoid this problem, umbilical artery Doppler blood flow velocity parameters were introduced to a fuzzy algorithm. It is observed that the fuzzy algorithm gives true results for interpretation of umbilical artery blood flow velocity parameters. Forty-five blood flow velocity parameters of 60 women with pregnancy and 15 parameters in training data have been used in a fuzzy system as testing data. The overall success ratio in training data and the testing data were 95.55 and 93.35% respectively.

Fetal heart rate and umbilical artery flow velocity variability in intrauterine growth restriction: a matched controlled study.

To study heart rate and umbilical artery blood flow velocity variability in growth-restricted fetuses and investigate the influence of the autonomic nervous system on these parameters. Doppler velocity waveforms were collected from long-lasting umbilical artery recordings in 15 fetuses with growth restriction and 15 normal age-matched controls at 23-35 weeks of gestation. Absolute heart rate and umbilical artery blood flow velocity as well as the coefficient of variation were determined. Using power spectral analysis the low- and high-frequency bands of heart rate variability and blood flow velocity variability were calculated. The low-to-high (LH) ratio of heart rate variability and blood flow velocity variability were examined as a measure of sympathovagal balance. In growth-restricted fetuses umbilical artery velocities were significantly reduced. Heart rate variability was significantly reduced in the presence of growth restriction, but no significant difference was demonstrated for blood flow velocity variability. The LH ratio for heart rate variability was significantly decreased in growth restriction, but no difference in LH ratio was demonstrated for blood flow velocity variability. Flow velocity variability in growth restriction seems not to be predominantly influenced by the autonomic nervous system, whereas the decreased heart rate variability seems to be influenced by altered sympathetic-parasympathetic balance.

Fetal heart rate and blood flow velocity variability in the presence of increased nuchal translucency: a preliminary study.

To study the power spectrum distribution of heart rate and umbilical artery flow velocity variability in fetuses with increased nuchal translucency thickness (NT). Doppler velocity waveforms were collected from long-lasting (>20 s) umbilical artery recordings in 18 fetuses with increased NT (>3 mm) and 18 normal controls matched for gestational age at 11-14 (median, 12) weeks. The NT group included 11 abnormal karyotypes: trisomy 18 (n = 3), 45,X (n = 4), trisomy 21 (n = 3) and a balanced translocation. Absolute heart rate as well as the coefficient of variation for both beat-to-beat heart rate variability and umbilical artery blood flow velocity variability were determined. The ratios of the integrated low-frequency components (0.05-0.2 Hz) and the integrated high-frequency ones (0.25-1.6 Hz; LH ratio) from normalized power spectrum distributions were established to reflect sympathovagal balance. The mean heart rate was not significantly different between the two groups. However, mean heart rate variability and time-averaged flow velocity variability were significantly increased in the NT group, while there was no significant difference in the LH ratios between the two groups. The mean umbilical artery pulsatility index was significantly higher in the NT group. The autonomic nervous system does not seem to play a role in the altered cardiovascular homeostasis in the presence of increased fetal NT.

Decreased vascularization and cell proliferation in placentas of intrauterine growth–restricted fetuses with abnormal umbilical artery flow velocity waveforms

Objective: The purpose of this study was to compare the morphologic features of placentas in severe intrauterine fetal growth restriction with abnormal umbilical artery blood flow velocity waveforms and normal gestation. Study Design: Immunohistochemical methods were used to evaluate cell proliferation, vascular density, and α-smooth muscle actin expression by stromal cells in a group of 9 age-matched intrauterine growth–restricted and control placentas at 25 to 41 weeks of gestation. Results: Fewer MIB1-positive nuclei were observed in both trophoblast and stromal cell populations in intrauterine growth restriction, which indicates fewer cells in cycle. Furthermore, a greatly reduced vascular density was observed, along with higher levels of α-smooth muscle actin expression in stromal cells. Conclusion: Intrauterine growth–restricted placentas show reduced cell proliferation in both trophoblast and stromal cell compartments. Peripheral villous vascularization is highly reduced. (Am J Obstet Gynecol 2002;187:764-9.)

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.