Umbilical Artery Flow Velocity Waveforms Research Articles

Labetalol Therapy in Pregnancy-Induced Hypertension: The Effects on Fetoplacental Circulation and Fetal Outcome

We prospectively studied the effects of oral labetalol therapy in patients with moderate to severe pregnancy induced hypertension (PIH). The outcome variables were blood pressure control, effect on umbilical artery flow velocity waveforms (UAFVW) and fetal outcome. Forty-two patients were recruited, all had moderate to severe PIH. The mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) on entry were 154 +/- 7 mmHg and 104 +/- 5 mmHg, respectively. All had significant proteinuria. After 1 week on labetalol therapy, 85% of patients had their blood pressure controlled. The reduction in both SBP and DBP was statistically significant. There were no significant changes in UAFVW, Resistance Index (RI), uric acid or platelets. The mean fetal age on entry was 246 +/- 10 days while gestation at delivery was 258 +/- 17 days. The mean birth weight was 2712 +/- 609 g. No perinatal mortality occurred in this study. Labetalol is an effective drug in controlling blood pressure and does not adversely affect the UAFVW. No neonatal problems were attributed directly to the drug. Fetal outcome was satisfactory despite the 12 fetuses that were growth-retarded. Labetalol allows safe prolongation of pregnancies complicated by PIH.

Acute maternal and fetal cardiovascular effects of caffeine ingestion.

Little data exist regarding the acute maternal and fetal cardiovascular effects of caffeine ingestion. The purpose of this study is assess the cardiovascular effects of caffeine ingestion in pregnant subjects and their fetuses. We examined seven caffeine-naive gravidas longitudinally at 25.7 (SE +/- 0.7) and 36.1 (+/- 0.7) weeks' gestation, before and after ingestion of a caffeine citrate solution (100 mg/m-2 body surface area). Maternal pulse, blood pressure, fetal heart rate, and fetal heart rate accelerations were determined before and after caffeine ingestion. Uterine artery, fetal aorta, and umbilical artery flow velocity waveforms were examined at similar intervals. Significant before and after caffeine differences, regardless of gestational age, were noted for maternal pulse (85.1 vs 74.2 beats/min), diastolic blood pressure (65.9 vs 73.8 torr), mean arterial blood pressure (81.5 vs 87.5 torr), uterine artery systolic-to-diastolic (S/D) ratio (1.9 vs 2.4), fetal heart rate (144.6 vs 135.4 beats/min), and fetal heart rate accelerations (1.6 vs 4.2 per 30 minutes). Differences for fetal aortic and umbilical artery S/D ratios were not significant with respect to caffeine administration. Fetal aortic peak velocities increased with caffeine (85.5 vs 130.2 cm/sec) and the increase was augmented with advancing gestational age. We conclude that maternal ingestion of modest amounts of caffeine citrate in caffeine-naive subjects significantly affects both the fetal and maternal cardiovascular systems.

The value of color Doppler ultrasound in the prenatal diagnosis of hypoplastic umbilical artery.

The prenatal diagnosis of hypoplastic umbilical artery has recently been reported, based on the visualization of discordant size between both umbilical arteries in association with discordant umbilical artery flow velocity waveforms. In this report we present two cases of hypoplastic umbilical artery and describe the use of color flow imaging and Doppler ultrasound in the prenatal evaluation of this condition. The principal advantages of these techniques include the confirmation of blood flow within the hypoplastic artery, thus ruling out the possibility of an atrophic non-functional artery, and the demonstration of size discrepancy at the level of the intra-abdominal portion of the umbilical arteries, validating the intra-amniotic cord findings. Color Doppler ultrasound is an important tool for diagnosing and evaluating vascular anomalies affecting the umbilical cord.

Fetal angiotensin II levels and vascular (type I) angiotensin receptors in pregnancies complicated by intrauterine growth retardation

Objective To investigate the status of the fetal renin-angiotensin system (RAS) in pregnancies complicated by severe intrauterine growth retardation (IUGR), and its possible relationship to elevated fetoplacental vascular resistance as indicated by abnormal umbilical artery Doppler flow velocity waveforms (FVW). Design Prospective survey of pregnancies falling into predefined categories and presenting at the Queen Mothers Hospital, Glasgow, over the study period. Subjects Effects of mode of delivery and gestational age were investigated using uncomplicated term pregnancies delivered vaginally (SVD group, n= 15) or by elective caesarean section (ECS group, n= 9), and normal pregnancies with spontaneous preterm onset of labour (PREM group, n= 6; normal birthweight for gestational age (31 weeks)). These groups were used as controls for the 13 IUGR cases delivered preterm (31 weeks) by caesarean section in the fetal interest. Main outcomes measures Umbilical artery FVW, birthweight, cord venous angiotensin II concentration ([cv ANG II]), fetoplacental vascular ANG II receptor concentration. Results Cord venous angiotensin II concentration was similar to maternal values in the ECS group (31–101 pmol/1, 95% CI), but was elevated (81–288 pmol/l, P= 0.03) after vaginal delivery. The concentration of ANG II receptors (type AT1, dissociation equilibrium constant, 1.27 nmol/l) in placental primary/secondary stem vascular tissue was lower in the SVD group (18–44 fmol/mg membrane protein, 95% CI), compared with the ECS group (29–122 fmol/mg, P= 0.03) consistent with acute receptor down-regulation by the elevated ANG II levels. No effect of gestational age on receptor number was demonstrable (P= 0.13, PREM (premature delivery) vs ECS group). In the IUGR group, [cv ANG II] (94–378 pmol/l) was markedly elevated compared with the ECS controls (P= 0.001) but receptor concentration (28–84 fmol/mg) was not significantly altered (P= 0.13). No relationships between [cv ANG II] or receptor number and umbilical artery FVW could be identified. No changes in receptor affinity were observed. Conclusion These results indicate activation of the fetal RAS in IUGR and suggest that responsiveness of the fetoplacental vasculature to the peptide is not diminished as would be expected from the elevated plasma ANG II levels. ANG II may contribute to the increased fetoplacental vascular resistance observed in this disorder, but does not apparently account for the abnormal umbilical artery FVW that is observed in a proportion of IUGR cases.

Erythrocytes in fetuses with abnormal umbilical artery flow velocity waveforms

Our purpose was to measure erythrocyte indexes in fetuses with two grades of Doppler-defined umbilical placental insufficiency. A prospective study comprising 110 infants categorized into control, moderate, and severe groups by umbilical artery waveform studies was undertaken at the University of Sydney at Westmead Hospital. Fetal erythrocyte indexes were measured in umbilical venous blood. Multivariate analyses of variance with post hoc Bonferroni t tests were used in the statistical analysis. The erythrocyte count, hematocrit, and hemoglobin concentration were all significantly higher (p < 0.001) in the two placental insufficiency groups than in the controls. Both placental insufficiency groups were affected to the same extent. Differences exist in the erythrocyte populations of fetuses with Doppler-defined placental insufficiency compared with controls. Importantly, these differences occur in more than just the most severe cases. These changes may represent a compensatory response to the placental vascular lesion detected by abnormal umbilical artery waveforms.

Labetalol therapy in pregnancy induced hypertension: the effects on fetoplacental circulation and fetal outcome

We prospectively studied the effects of oral labetalol therapy in patients with moderate to severe pregnancy induced hypertension (PIH). The outcome variables were blood pressure control, effect on umbilical artery flow velocity waveforms (UAFVW) and fetal outcome. Forty-two patients were recruited, all had moderate to severe PIH. The mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) on entry were 154 ± 7 mmHg and 104 ± 5 mmHg, respectively. All had significant proteinuria. After 1 week on labetalol therapy, 85% of patients had their blood pressure controlled. The reduction in both SBP and DBP was statistically significant. There were no significant changes in UAFVW, Resistance Index (RI), uric acid or platelets. The mean fetal age on entry was 246 ± 10 days while gestation at delivery was 258 ± 17 days. The mean birth weight was 2712 ± 609 g. No perinatal mortality occurred in this study. Labetalol is an effective drug in controlling blood pressure and does not adversely affect the UAFVW. No neonatal problems were attributed directly to the drug. Fetal outcome was satisfactory despite the 12 fetuses that were growth-retarded. Labetalol allows safe prolongation of pregnancies complicated by PIH.

Correlation between umbilical artery resistance index, 6 ketoprostaglandin F1 α and thromboxane B 2 in the fetoplacental compartment in patients with pregnancy induced hypertension

Umbilical artery flow velocity waveforms (UAFVW's) were measured by Doppler ultrasound in 35 pregnant women with pregnancy induced hypertension. The stable hydration products of the vasoconstrictor and proaggregatory thromboxane A 2 and vasodilatory and anti-aggregatory prostacyclin (i.e. thromboxane B 2 (TxB 2) and 6 ketoprostaglandin F 1 α (6 keto PGF 1 α ) respectively) were measured in blood obtained from the umbilical vein and were assayed by radioimmunoassay. Abnormal umbilical artery Resistance Index (UARI) was associated with higher thromboxane B 2 levels, lower 6-ketoprostaglandin F 1 α levels and lower 6-keto PGF 1α TxB 2 ratio. Moreover, the umbilical artery Resistance Index was significantly correlated with the 6-keto PGF 1α thromboxane B 2 ratio suggesting an association between abnormal umbilical artery blood flow and altered prostacyclin/thromboxane balance in the fetoplacental compartment in patients with pregnancy induced hypertension (PIH).

Plasma endothelin, atrial natriuretic peptide (ANP) and uterine and umbilical artery flow velocity waveforms in hypertensive pregnancies

Objective To investigate the relation between concentrations of endothelin and atrial natriuretic peptide (ANP) in maternal plasma and vasospasm in the uterine and umbilical arteries as detected by duplex pulsed colour Doppler ultrasonography in hypertensive pregnancies. Design An observational study. Subjects 32 women admitted consecutively to hospital with pregnancy induced hypertension (seven without proteinuria and 25 with proteinuria) and 78 healthy pregnant women examined at 28–0 weeks gestation. Main outcome measures Systolic/diastolic (S/D) ratio in flow velocity waveforms (FVWs) and plasma concentrations of endothelin and ANP in the 32 women with pregnancy induced hypertension; plasma concentrations of endothelin and ANP in 78 healthy pregnant women (controls). Results Pathological FVWs suggesting vasospasm in the uterine or umbilical artery, or both arteries, were found in 12 women with hypertension. Plasma ANP was significantly higher (P= 0.03) in the women with hypertension and pathological FVWs (median 23.0, range 10.1–52.8 pmol/1) than in those with hypertension and normal FVWs, (median 13.8, range 5.3–42.3 pmol/1) but corresponding plasma endothelin levels did not show any significant difference (median 1.63, range 0.51–3.33 pmol/1 and median 1.38, range 0.51–3.51 pmol/1, respectively). Conclusion Local release of endothelin from the vascular endothelium is thought to cause vasospasm in pregnancy induced hypertension but this does not seem to increase the concentration of endothelin in the maternal peripheral plasma, probably because of its rapid disappearance from the blood circulation. As ANP dilates the blood vessels, the increase of its release in hypertensive pregnancies may be a compensatory mechanism against vasospasm.

Fetal angiotensin II levels and vascular (type I) angiotensin receptors in pregnancies complicated by intrauterine growth retardation.

To investigate the status of the fetal renin-angiotensin system (RAS) in pregnancies complicated by severe intrauterine growth retardation (IUGR), and its possible relationship to elevated fetoplacental vascular resistance as indicated by abnormal umbilical artery Doppler flow velocity waveforms (FVW). Prospective survey of pregnancies falling into predefined categories and presenting at the Queen Mothers Hospital, Glasgow, over the study period. Effects of mode of delivery and gestational age were investigated using uncomplicated term pregnancies delivered vaginally (SVD group, n = 15) or by elective caesarean section (ECS group, n = 9), and normal pregnancies with spontaneous preterm onset of labour (PREM group, n = 6; normal birthweight for gestational age (31 weeks)). These groups were used as controls for the 13 IUGR cases delivered preterm (31 weeks) by caesarean section in the fetal interest. Umbilical artery FVW, birthweight, cord venous angiotensin II concentration ([cv ANG II]), fetoplacental vascular ANG II receptor concentration. Cord venous angiotensin II concentration was similar to maternal values in the ECS group (31-101 pmol/l, 95% CI), but was elevated (81-288 pmol/l, P = 0.03) after vaginal delivery. The concentration of ANG II receptors (type AT1, dissociation equilibrium constant, 1.27 nmol/l) in placental primary/secondary stem vascular tissue was lower in the SVD group (18-44 fmol/mg membrane protein, 95% CI), compared with the ECS group (29-122 fmol/mg, P = 0.03) consistent with acute receptor down-regulation by the elevated ANG II levels. No effect of gestational age on receptor number was demonstrable (P = 0.13, PREM (premature delivery) vs ECS group). In the IUGR group, [cv ANG II] (94-378 pmol/l) was markedly elevated compared with the ECS controls (P = 0.001) but receptor concentration (28-84 fmol/mg) was not significantly altered (P = 0.13). No relationships between [cv ANG II] or receptor number and umbilical artery FVW could be identified. No changes in receptor affinity were observed. These results indicate activation of the fetal RAS in IUGR and suggest that responsiveness of the fetoplacental vasculature to the peptide is not diminished as would be expected from the elevated plasma ANG II levels. ANG II may contribute to the increased fetoplacental vascular resistance observed in this disorder, but does not apparently account for the abnormal umbilical artery FVW that is observed in a proportion of IUGR cases.

Low target birth weight or growth retardation? Umbilical Doppler flow velocity waveforms and histometric analysis of fetoplacental vascular tree

The placental vascular architecture of small-for-gestational-age fetuses seems to have an impact on the flow patterns in the umbilical arteries. Blood flow velocity waveforms of the umbilical arteries were measured by Doppler ultrasonography in nine small-for-gestational-age fetuses with elevated systolic/diastolic ratios of the umbilical arteries, seven small-for-gestational-age fetuses with normal flow patterns, and 14 appropriate-for-gestational-age fetuses with normal flow patterns. After delivery histomorphometric placental investigations were performed. Reduced end-diastolic flow velocities were significantly associated with both a reduction of vascularization within the terminal villi and adverse diffusion conditions, indicating insufficient functional maturity. The perfusion and diffusion capacity of small-for-gestational-age placentas with normal umbilical artery flow velocity waveforms was similar or even slightly better compared with the appropriate-for-gestational-age control values. These data suggest that Doppler flow velocimetry in the umbilical arteries is predictive of a vascular lesion within the placentas of small-for-gestational-age fetuses.

The value of Doppler ultrasound studies within the scope of obstetric management in unexpected findings in the cardiotocograph

In a study of 30 cases with moderate or serious foetal heart rate alterations, we examined the influence of Doppler ultrasound on our obstetrical management. Normal results of Doppler umbilical artery flow velocity waveform analysis would allow us in 22 of 24 cases, to continue the pregnancy under usual control. Only in two cases with moderate foetal heart rate alterations, absence of labour and a normal Doppler result, Caesarean section was necessary because of foetal distress. A pathological Doppler result was found in six cases with intrauterine growth retardation. These risks were not known prior to the patients hospitalisation. Surprisingly, we found only moderate foetal heart rate alterations in these cases. Without any further control of the foetal heart rate, we decided to perform Caesarean section immediately after the Doppler investigation. We are of the opinion, that Doppler ultrasound could be very useful in obstetrical management to decide, if the pregnancy must be ended or could possibly be continued in cases of premature birth.

Doppler Ultrasonography of the Umbilical Cord in Normal Pregnancy

Using continuous wave Doppler ultrasonography to measure umbilical artery flow velocity waveforms (FVWs) is a safe, noninvasive means of quantifying placental resistance to blood flow. Detection of abnormally elevated resistance to umbilical perfusion may identify pregnancies complicated by uteroplacental insufficiency. Use of this technique to identify high-risk pregnancies requires ready access to standard tables of normal FVW values obtained from well-defined populations under usual clinical conditions. We report measurements of the systolic-diastolic (S-D) ratio of the umbilical artery obtained between 16 and 43 weeks in 122 normal pregnancies. A gestational-age-adjusted table of normal values is presented.

Umbilical and uterine artery flow velocity waveforms in pregnant women with systemic lupus erythematosus treated with aspirin and glucocorticosteroids.

Pregnancy in systemic lupus erythematosus (SLE) is at high risk to the mother and fetus. Impaired utero-placental perfusion may increase fetal loss and intrauterine growth retardation. We assessed the changes in impedance to blood flow in the umbilical and uterine arteries in five patients with SLE treated with low dose aspirin and corticosteroids, using Doppler ultrasound longitudinally throughout pregnancy. Blood flow velocity waveforms of the umbilical and uterine arteries were studied by transabdominal and transvaginal Doppler ultrasound, respectively. Resistance index (RI) was measured every two to four weeks from week 10 to term, and the values obtained were compared to those of normal pregnancies. All five patients delivered uneventfully. One neonate was delivered at 36 weeks (2550 g) and one neonate was growth retarded (1900 g at 38 weeks). Three women delivered at 39 weeks (3585 g, 2850 g, and 2800 g). Most umbilical artery RI values obtained throughout pregnancy were above the 95th percentile of normal pregnancies. The highest values of RI of the umbilical artery were assessed in the case of fetal growth retardation. However, most measurements of RI of the uterine artery were under the 95th percentile of normal. The improved pregnancy outcome in patients with SLE treated with aspirin and corticosteroids seems to correlate with their normal uterine artery flow velocity wave forms.

Plasma endothelin, atrial natriuretic peptide (ANP) and uterine and umbilical artery flow velocity waveforms in hypertensive pregnancies.

To investigate the relation between concentrations of endothelin and atrial natriuretic peptide (ANP) in maternal plasma and vasospasm in the uterine and umbilical arteries as detected by duplex pulsed colour Doppler ultrasonography in hypertensive pregnancies. An observational study. 32 women admitted consecutively to hospital with pregnancy induced hypertension (seven without proteinuria and 25 with proteinuria) and 78 healthy pregnant women examined at 28-40 weeks gestation. Systolic/diastolic (S/D) ratio in flow velocity waveforms (FVWs) and plasma concentrations of endothelin and ANP in the 32 women with pregnancy induced hypertension; plasma concentrations of endothelin and ANP in 78 healthy pregnant women (controls). Pathological FVWs suggesting vasospasm in the uterine or umbilical artery, or both arteries, were found in 12 women with hypertension. Plasma ANP was significantly higher (P = 0.03) in the women with hypertension and pathological FVWs (median 23.0, range 10.1-52.8 pmol/l) than in those with hypertension and normal FVWs, (median 13.8, range 5.3-42.3 pmol/l) but corresponding plasma endothelin levels did not show any significant difference (median 1.63, range 0.51-3.33 pmol/l and median 1.38, range 0.51-3.51 pmol/l, respectively). Local release of endothelin from the vascular endothelium is thought to cause vasospasm in pregnancy induced hypertension but this does not seem to increase the concentration of endothelin in the maternal peripheral plasma, probably because of its rapid disappearance from the blood circulation. As ANP dilates the blood vessels, the increase of its release in hypertensive pregnancies may be a compensatory mechanism against vasospasm.

Condition at birth of infants with previously absent or reverse umbilical artery end-diastolic flow velocities

In a case control study we assessed 47 fetuses with absent or reverse end-diastolic flow velocities (AREDFV) of the umbilical artery with respect to the mode of delivery, fetal acidosis, and abnormal neurological evaluations at the time of discharge from the department of pediatrics. We also studied a control group which was matched for gestational age and had normal umbilical artery flow velocity waveforms. Fetuses with AREDFV were delivered almost exclusively by cesarean section which was usually done for fetal distress. The number of fetuses with abnormal neurological signs was significantly increased compared to the control group. Fetuses with AREDFV showed an increased incidence of fetal acidosis. Forty per cent of these fetuses were delivered within one day of the first abnormal flow measurement; Sixty per cent were observed clinically for up to four weeks before delivery.

Quantitation of breathing-related modulation of umbilical arterial and venous flow velocity waveforms in the normal term fetus

The effect of fetal breathing activity on umbilical arterial and venous flow velocity waveforms was studied in 11 normal pregnant subjects at term during fetal behavioural state 2F (Nijhuis et al. Early Hum Dev 1982;6:177–195). A total of 1041 breathing cycles was evaluated. Our data suggest a net reduction in venous flow velocity during fetal breathing activity. In contrast to venous flow velocity, the magnitude of breathing-related modulation of arterial pulsatility is small and independent of breathing amplitude. Nevertheless, for clinical purposes umbilical arterial flow velocity waveform recording during fetal apnea is recommended.

Blood flow velocity waveforms of the middle cerebral artery and abnormal neurological evaluations in live-born fetuses with absent or reverse end-diastolic flow velocities of the umbilical arteries

We studied 37 fetuses with absent or reverse end-diastolic flow velocities (AREDFV) of the umbilical arteries with respect to the mode of delivery, fetal acidosis, resistance index of the middle cerebral arteries, and abnormal neurological evaluation at the time of discharge from the department of pediatrics. A control group with normal umbilical artery flow velocity waveforms was matched for gestational age. Fetuses with AREDFV were delivered almost exclusively by cesarean section, in most cases due to fetal distress. Metabolic changes with decreased base excess values were found more often in fetuses with AREDFV, but no difference could be detected with respect to severe fetal acidosis. The number of fetuses with abnormal neurological evaluations during the first 6 months of life was significantly higher in cases with AREDFV than in the control group. More than two thirds of the fetuses with AREDFV showed an abnormal blood flow velocity waveform of the middle cerebral arteries with elevated end-diastolic flow velocities. The combination of extreme premature delivery before 28 weeks of gestation, severe idiopathic respiratory distress syndrome, and a resistance index of the middle cerebral arteries under the 5th percentile seems to be a risk factor for early neurological morbidity in fetuses with AREDFV. Premature delivery of fetuses with AREDFV — as we did during our study in order to prevent intra-uterine death or fetal asphyxia — should therefore be critically regarded in cases under 28 weeks of gestational age and abnormal flow velocity waveforms of the middle cerebral arteries.

Umbilical artery and uteroplacental velocimetry in pregnancies complicated by idiopathic low birthweight centile.

Umbilical artery and uteroplacental Doppler flow velocity waveforms were studied in 35 pregnancies complicated by idiopathic low birthweight centile. Thirty fetuses (86%) were below the 5th centile birthweight for gestation. Fifteen (43%) had an abnormal umbilical artery systolic to diastolic ratio. Uteroplacental waveforms were recorded in 29 of the 35 pregnancies and five (17%) showed an abnormal systolic to diastolic ratio. Abnormal uteroplacental systolic to diastolic ratios were associated with a significantly earlier gestational age at delivery and significantly more cesarean sections for fetal distress compared with normal uteroplacental systolic to diastolic ratios (p less than or equal to 0.01). The absence of umbilical artery end-diastolic frequencies was associated with a significantly earlier gestational age at delivery compared with the presence of umbilical artery end-diastolic frequencies (p less than 0.005). No differences in pregnancy outcome were observed comparing normal with abnormal amniotic fluid volume assessment. These findings suggest that Doppler studies may be useful in estimating the risk of adverse perinatal outcome for small for gestational age fetuses with no identifiable cause.

Effects of Extradural Anesthesia on Umbilical and Uteroplacental Arterial Flow Velocity Waveforms

Effects of Extradural Anesthesia on Umbilical and Uteroplacental Arterial Flow Velocity Waveforms

Doppler blood flow changes and placental morphology in pregnancies with third trimester hemorrhage.

Combined real-time ultrasound and pulsed Doppler ultrasound examinations were performed in 67 patients with third trimester hemorrhage and other symptoms related to placental abruption, starting from the onset of symptoms to delivery. In 52 of the cases, placental morphology was investigated by light microscopy. Thirteen patients were ultimately given the diagnosis abruptio placentae. None of the morphological placental changes considered had any statistical relationship to placental abruption. Patients with placental centrocotyledon hemorrhages and infarction more often had abnormal umbilical artery flow velocity waveforms at the onset of symptoms, and more frequent abnormal arcuate artery flow velocity waveforms were found among those with placental infarction alone. Abnormal flow velocity waveforms in the umbilical and arcuate arteries were associated with placental abruption, both at the onset of symptoms and at the final examination before delivery. The results indicate an increased risk for placental abruption if the arcuate and/or umbilical artery flow velocity waveforms are abnormal in patients with third trimester hemorrhage.