Uterine and fetal umbilical artery flow velocity waveforms in normal first trimester pregnancies

In 85 normal singleton pregnancies between 8 and 13 weeks gestation, Doppler flow velocity waveform recordings were attempted from the left and right uterine artery and fetal umbilical artery. Acceptable waveforms were obtained from the uterine arteries in 83 and from the fetal umbilical artery in 61 of the 85 pregnancies. There was virtually no difference between the left and right uterine artery on average. The marked decrease in pulsatility (PI) and resistance (RI) indices from both uterine arteries reflects the ongoing process of secondary trophoblast invasion into the muscular part of the spiral arteries. Absent end-diastolic velocities were observed in 59 of 61 fetal umbilical artery flow velocity waveform recordings. PI values from the fetal umbilical artery suggest unaltered umbilical placental vascular resistance during the first trimester of pregnancy.     

Fetal brain sparing is strongly related to the degree of increased placental vascular impedance

BACKGROUND: Doppler ultrasound examination has become an established method of clinical surveillance in high-risk pregnancies. Doppler indication of fetal brain sparing (BS) is an acknowledged sign of circulation redistribution during chronic hypoxia. OBJECTIVES: To evaluate the relationship between placental vascular resistance and signs of BS in middle cerebral artery (MCA) blood flow velocity. METHODS: The MCA, uterine artery, and umbilical artery (UA) were located by color Doppler ultrasound in 103 high-risk pregnancies at risk for intrauterine fetal hypoxia. The blood velocity spectrum was analyzed for the following parameters: pulsatility index (PI) and signs of notching in the uterine arteries. Z-score was calculated for the MCA PI. RESULTS: Signs of BS in the MCA were correlated to increased placental vascular impedance. The degree of BS in the MCA expressed as Z-scores was correlated to increasing vascular impedance, both in the umbilical and uterine arteries, and to adverse outcome of pregnancy. The greatest deviation in MCA PI Z-scores was seen in preterm pregnancies. CONCLUSION: A clear correlation exists between increasing placental vascular impedance and BS in the MCA. Preterm pregnancies express the greatest deviation from the mean MCA PI.     

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.     

Umbilical and uterine flow velocity waveforms in pregnancies complicated by major fetal anomalies

A continuous wave Doppler unit was used to obtain umbilical and uterine artery flow velocity waveforms in pregnancies complicated by a major fetal abnormality. A total of 139 examinations were performed on 32 women between 26 to 41 weeks' gestation, and the records were reviewed to determine the changes associated with fetal malformation. The systolic/diastolic (A/B) ratio was used as an index of blood flow resistance in the umbilical artery and the systolic minus diastolic divided by systolic (A-B)/A for the branches of the uterine artery. Seventeen out of 32 patients showed high systolic/diastolic ratio in waveforms taken from the umbilical artery. In 30 out of 32 patients the uterine artery waveform was normal (in two patients the results were equivocal). It appears that a fetal mechanism may determine the changes in the umbilical placental circulation resulting in an umbilical artery pattern of high flow resistance in more than half of the patients with congenital anomalies.     

Fetal superior mesenteric artery blood flow velocimetry in normal and high-risk pregnancy

THE AIM: To record blood flow velocimetry in the fetal superior mesenteric artery in normal pregnancy and to evaluate if blood flow recordings in the vessel might predict adverse outcome in high-risk pregnancy. METHODS: The fetal superior mesenteric artery blood velocimetry was recorded in a cross sectional manner in 75 normal pregnancies between 27 and 41 weeks of gestation. Reference curves were performed for pulsatility and resistance indices. The superior mesenteric artery was also located in 48 singleton pregnancies complicated by pregnancy-induced hypertension and/or intra-uterine growth retardation. Middle cerebral artery, umbilical artery and vein and uterine artery velocimetry were also recorded. RESULTS: Superior mesenteric artery PI and RI values expressed an increase in resistance to blood flow with gestational age after 32 weeks of gestation. In all except eight high-risk pregnancies the fetal mesenteric artery PI values were within normal range. Among the pregnancies with absent or reversed blood flow in the umbilical artery, all had abnormal mesenteric artery pulsatility index (PI) (> 97.5th percentiles), one fetus died intrauterine and two others died after delivery due to prematurity, growth retardation and necrotizing enterocolitis. In the remaining fetuses with increased mesenteric artery PI, necrotizing enterocolitis was diagnosed in three cases. CONCLUSIONS: Increased vascular resistance in the mesenteric artery might be a late sign of fetal circulation redistribution and frequently related to necrotizing enterocolitis in the newborn.     

Uteroplacental blood flow velocity-time waveforms in normal and complicated pregnancy

Summary. A simple continuous wave Doppler ultrasound system for recording arterial flow velocity waveforms in branches of the uterine artery in the placental bed is described. Twelve normal pregnancies were studied serially from 20 weeks to delivery. The diastolic flow velocity expressed as a percentage of the systolic provides an index of downstream vascular bed resistance and perfusion. This always exceeded 50% in normal pregnancy and there was a small increase with gestational age indicative of a decreasing flow resistance. Of the 91 complicated pregnancies, studied because of potential uteroplacental insufficiency and fetal risk, 25 resulted in the birth of an infant small-for-gestational-age. In 15 the uterine artery flow velocity waveform revealed a pattern of low diastolic flow velocity. It is postulated that these represent a subgroup of growth-retarded fetuses in whom there is reduced uterine artery perfusion. Reduced uterine artery diastolic flow velocity in these patients was associated with reduced umbilical artery diastolic flow velocity on the fetal side of the placenta. In contrast the 10 small-for-gestation infants associated with normal uterine artery waveforms suggest a primary fetal cause. Twelve patients with severe hypertensive disease of pregnancy were studied. Nine were associated with reduced uterine artery diastolic flow velocity (reduced uterine artery perfusion) consistent with vasospasm in the branches of the uterine artery in the placental bed.     

Umbilical artery flow velocity waveforms and cord blood viscosity.

The role of cord blood viscosity in determining the umbilical artery Doppler flow velocity waveform (FVW) was investigated in 22 normal pregnancies and 29 complicated pregnancies. FVWs were quantified by calculating the pulsatility index (PI). There was a significant correlation between an abnormal PI (more than 2 SD from the mean) and fetal growth retardation (less than 5th birthweight centile), cesarean section for fetal distress, and raised cord blood hematocrit. However, there was no relationship between whole blood or plasma viscosity measurements and the umbilical artery PI.     

Flow velocity waveforms in the maternal uteroplacental and fetal umbilical placental circulations

A simple continuous-wave Doppler ultrasound system was used to record arterial flow velocity time waveforms from branches of the maternal uterine artery in the placental bed and the fetal umbilical arteries. The systolic-diastolic ratio of flow velocities was measured as an index of peripheral resistance. In normal pregnancy both circulations exhibit high diastolic flow velocities caused by low resistance. The study group consisted of 172 pregnancies with high fetal risk of which 53 resulted in delivery of a small-for-gestational age infant. The last study-to-delivery interval was less than 10 days. In the small-for-gestational age fetuses in whom both umbilical and uterine studies were normal there was good fetal outcome (19 cases). Neonatal morbidity occurred among those with abnormal umbilical studies with low diastolic flow velocities, indicating high resistance. Of these studies there were two subgroups. An abnormal uterine study (13 cases) indicated a primary maternal uteroplacental lesion and a normal study (21 cases) a primary fetal lesion. In cases of severe maternal hypertension, abnormal uterine artery waveforms were associated with abnormal umbilical artery waveforms.     

Doppler measurements in fetoplacental vessels after maternal betamethasone administration

OBJECTIVE: To observe the influence of maternal betamethasone administration for fetal lung maturation on the arterial, venous and intracardiac blood flow of the fetus and the uterine arteries. METHODS: Twenty-seven women with singleton pregnancies were examined before the first, and 30 min and 8, 24, 48 and 72 h after the second of two single doses of 8 mg of betamethasone. We recorded blood flow velocity waveforms of the umbilical artery (UA), the middle cerebral artery, the uterine arteries, the ductus venosus, the inferior vena cava and the right hepatic vein, the pulmonary trunk, the ductus arteriosus and the right and left intraventricular inflow of the heart. RESULTS: The resistance index of the UA showed a significant transient decrease 30 min (p = 0.024) after the second betamethasone dose. The peak systolic velocity of the ductus arteriosus increased significantly 30 min after the 2nd dose (p = 0.009) and then returned to non-significant values. No significant change was observed in any of the other vessels. CONCLUSION: Betamethasone causes short-term changes in fetal blood flow. However, this effect seems to be mild and reversible and does not appear to contraindicate the use of corticosteroids to promote fetal lung maturation.     

Effects of therapeutic amniocentesis on uterine and umbilical artery velocimetry in cases of severe symptomatic polyhydramnios

The objective of this study was to determine the effects of removal of amniotic fluid in cases of symptomatic severe polyhydramnios on Doppler waveform indices of the uterine and umbilical arteries and flow velocities of the uterine arteries. Nine women underwent therapeutic amniocentesis during ten pregnancies for symptomatic polyhydramnios due to Beckwith-Wiedemann Syndrome (n = 1), esophageal atresia (n = 2), chorioangioma (n = 1), twin–twin transfusion syndrome (n = 3), a presumed autosomal recessive syndrome (n = 2), and an unbalanced double translocation (n = 1; partial dup 3q and partial del 9p syndrome). An average of 2.78 ± 0.9 (range 1–4) 1 of fluid were removed at each procedure between the gestational ages of 18 and 34 weeks (mean of 28 weeks). The systolic/diastolic (S/D) ratio, pulsitility index (PI), and resistance index (RI) of the uterine and umbilical arteries were obtained before and after the procedure using color and pulsed Doppler. After angle correction, the peak systolic velocity (PSV) and mean velocity (MV) in centimeters/second (cm/s) of the uterine arteries were also determined. The presence or absence of a uterine artery waveform notch was determined. Dominant uterine arteries were defined as those with lower impedance indices or higher flow velocities. Statistical analysis was performed with the Wilcoxon signed-rank test. Significance was set at P < 0.05. There was a significant increase in the median value of the uterine artery MV (43.8 vs. 81.1 cm/s, P = 0.005) and PSV (74.2 vs. 125.5 cm/s, P = 0.007) after amniocentesis. The uterine S/D (3.0 vs. 1.84, P = 0.007), PI (1.12 vs. 0.68, P = 0.008), and RI (0.60 vs. 0.45, P = 0.005) impedance indices significantly decreased following amniocentesis. When uterine arteries were categorized as dominant vs. nondominant, there were greater improvements in impedance indices and flow velocities in the nondominant uterine arteries. There were three cases of unilateral and one case of bilateral early diastolic notches of the uterine artery waveforms which either resolved (n = 4) or improved (n = 1). There was no effect on the umbilical artery impedance indices. Therapeutic amniocentesis significantly improved uterine artery impedance indices and resulted in improved flow velocities, while there was no effect on umbilical artery waveform indices. The procedure resulted in the disappearance or improvement of the uterine waveform notch. Our findings suggest that in cases of severe polyhydramnios abnormal uterine artery velocimetry may not be due to lack of trophoblastic invasion of the spiral arteries but to increased intrauterine pressure secondary to polyhydramnios.     

The usefulness of uterine artery doppler velocimetry in high risk pregnancy diagnostic (PIH and/or IUGR)

OBJECTIVES: High risk pregnancy was defined as developing of pregnancy induced hypertension or/and growth retardation in the course of gestation. DESIGN: The main aim of the study is to analyze the usefulness of uterine artery doppler velocimetry in high risk pregnancy diagnostic. MATERIALS AND METHODS: 610 single pregnancies were included in the study. First group of normal pregnancies where -530 single normal pregnancies between 19 and 39 gestation weeks. S/D, RI & PI in both uterine arteries were assessed. There were assessed flow velocity waveforms also for detection of notches. At the next stage an examined group with 80 pregnant women was formed where in the course of gestation pregnancy induced hypertension and/or fetal growth retardation. 24 hour monitoring of the blood pressure in the examined group was performed. Obtained data from both groups was calculated and statistically analyzed. RESULTS: Mean values for flow velocity waveform indices were estimated for both groups: controls S/D 2,35 (SD 0,61), RI 0,56 (SD 0,11), PI 0,96 (SD 0,32), examined group S/D 2,99 (SD 1,16), RI 0,63 (SD 0,12), PI 1,26 (SD 0,51). There is significant difference between values for all flow parameters p < 0,001. In the control group we observed notches in 11,8% of all women and in the examined (hypertension and/or growth restriction) group in 81,3% (p<0,001). The sensitivity is 81,3% and specificity 88,2%. MoMRIs for both uterine arteries were calculated to compare data from control and examined group. In the examined group 41,3% RI results were above calculated MoM and there is significant difference between both groups (p <0,001). The sensitivity is 41,3% and specificity 89,5%. In the group of the hypertensive pregnant women where mean systolic blood pressure in 24 hour monitoring was above 130 mm Hg we observed notches in 61,1% of flow velocity waveforms in uterine arteries. In the group of normal pregnancies there were 11,8% notches and there is significant difference between both groups (p<0,001). CONCLUSIONS: The uterine artery velocimetry values of S/D, RI, PI decrease with the progression of gestation. There are no significant differences between right and left uterine artery doppler velocimetry. There are significant differences for values and percentage of notches in both groups. Extremely high rate of notches is observed in the group with most elevated blood pressure (daily mean value over 130mm Hg). It is possible to calculate obstetrical risk assessing values for blood flow in uterine arteries in pregnancy. It can be helpful to estimate methods detecting elevated risk for hypertension and/or growth retardation in pregnancy.     

Umbilical artery and uteroplacental blood flow velocity waveforms in normal pregnancy--a cross-sectional study

Umbilical and arcuate artery blood flow velocity waveforms (FVW) were recorded in 125 normal singleton pregnancies from 20 to 42 weeks of gestation. The FVW were analysed for pulsatility index (PI), peak systolic velocity/minimum diastolic velocity ratio (S/D ratio), rising slope (RS) and descending slope (DS). Both in the umbilical and arcuate arteries, values for all variables declined with advancing gestation, indicating decreasing placental vascular resistance. The umbilical artery PI was unaffected by the fetal heart rate, but the arcuate artery PI was negatively correlated to the maternal heart rate (r = -0.40). The arcuate artery PI decreased by 0.00394 with each beat per minute increase in maternal heart rate. Normal limits (mean +/- 2 SD) were established for umbilical artery PI corrected for gestational age, and arcuate artery PI corrected for gestational age and maternal heart rate.     

Umbilical and uterine artery flow velocity waveforms in pregnancy associated with major fetal abnormality

Flow velocity waveforms from the umbilical artery and branches of the uterine artery in the placental bed were recorded using continuous wave Doppler ultrasound. The records of 26 patients with pregnancy complicated by major fetal abnormality were reviewed to determine the changes of a primary fetal disturbance. The systolic/diastolic (A/B) ratio was used as an index of blood flow resistance. In 13 of the 26 patients the umbilical artery waveform systolic/diastolic ratio was high. It is postulated that in these patients there is a process of obliteration of small arteries in the placenta that is triggered by the abnormal fetus. In all patients the uterine artery waveform was normal. In seven of these 13 patients the infant had a birthweight greater than 10th centile. Placental weights were examined. A small placenta expressed as either low weight for gestational age or low placental/fetal weight ratio was associated with a normal umbilical artery waveform. It is suggested that fetuses in these groups have a low growth potential. In contrast a high placental/fetal weight ratio was associated with an abnormal umbilical artery waveform pattern.     

Ultrasound Doppler evaluation of uteroplacental and fetoplacental circulation in pre-eclampsia

Summary Blood flow velocity waveforms (FVW) were recorded weekly from the umbilical and arcuate arteries in 58 hospitalised women with a pregnancy complicated by pre-eclampsia. The maximum velocity waveform was analysed for pulsatility index (PI) and the results from the final antenatal examination were related to the outcome of pregnancy. The umbilical artery FVW was abnormal in 36% of the pre-eclamptic pregnancies, as was the arcuate artery FVW in 42%. No difference in FVW was found between mild and severe pre-eclampsia. Abnormal FVW in the umbilical artery was associated significantly both with intra-uterine growth retardation (IUGR) (P<0.001) and with signs of fetal distress (FD) (P<0.05). Abnormal arcuate artery FVW was associated with FD (P<0.05), but not with IUGR. The outcome of pregnancy was related to Placenta Waveform Class, which was derived from the blood velocity on both maternal and fetal sides of placenta. The results suggest that ultrasound Doppler examination of the umbilical artery is a useful aid in monitoring pregnancies complicated by preeclampsia, but that arcuate artery examination needs further evaluation.     

Doppler sonographic examinations of uteroplacental, fetoplacental, and fetal hemodynamics and their prognostic value in preterm labor.

Doppler examinations of different uteroplacental vessels (uterine arteries, arcuate arteries), umbilical artery, fetal thoracic aorta, and median cerebral artery were performed on 55 patients with idiopathic preterm labor (24.5 to 32.5 weeks). Thirty normal pregnancies of corresponding gestational age served as a control group. Significant differences of median values between the preterm labor and control group were found only for the resistance index (RI) in the central arcuate artery and for the pulsatility index (PI) in the fetal thoracic aorta. In about twenty percent of pregnancies in preterm labor, pathological values of RI and PI in uteroplacental and fetal vessels account for the presence of an impaired perfusion. Elevated PI in the uterine artery placental site and normal RI in the fetal thoracic aorta, correlate significantly to a shorter prolongation of pregnancy, lower gestational age on birth, and lower birth weight. The combination of these two blood flow indices (maternal PI greater than 0.90 and fetal RI less than 0.90) allow us to predict a preterm birth in a high percentage of cases (sensitivity 87.5%, specificity 100%, positive predictive value 100%, negative predictive value 93%).     

Umbilical and uterine artery flow velocity waveforms in pregnancy associated with major fetal abnormality

Summary. Flow velocity waveforms from the umbilical artery and branches of the uterine artery in the placental bed were recorded using continuous wave Doppler ultrasound. The records of 26 patients with pregnancy complicated by major fetal abnormality were reviewed to determine the changes of a primary fetal disturbance. The systolic/diastolic (A/B) ratio was used as an index of blood flow resistance. In 13 of the 26 patients the umbilical artery waveform systolic/diastolic ratio was high. It is postulated that in these patients there is a process of obliteration of small arteries in the placenta that is triggered by the abnormal fetus. In all patients the uterine artery waveform was normal. In seven of these 13 patients the infant had a birthweight > 10th centile. Placental weights were examined. A small placenta expressed as either low weight for gestational age or low placental/feta1 weight ratio was associated with a normal umbilical artery waveform. It is suggested that fetuses in these groups have a low growth potential. In contrast a high placental/fetal weight ratio was associated with an abnormal umbilical artery waveform pattern.     

Placental ischemia and changes in umbilical and uteroplacental arterial and venous hemodynamics

Objective: To relate Doppler velocimetry findings in fetoplacental and uteroplacental circulation to placental histomorphology. Material and methods: In 14 uncomplicated and 31 high-risk pregnancies Doppler velocimetry was performed in umbilical artery and vein, and in maternal uterine veins and arteries during the second half of gestation. Histopathology of the placentas was examined, especially for signs of ischemia and inflammation. Results: All fetuses in uncomplicated pregnancies had normal flow velocity waveforms in umbilical artery; in the high-risk group, 18 fetuses had abnormal flow (increased PI or absent/reverse end-diastolic flow). The latter group had more often high ischemic score and infarctions in the placenta than found in pregnancies with normal umbilical artery flow (p?<?0.001 and p?=?0.02, respectively). Similarly, the abnormal uterine artery flow pattern (uterine artery score 3–4) occurred more often with high ischemic score and placenta infarctions (p?<?0.001 and p?<?0.001, respectively). No significant associations were found between the uterine venous flow type and placental ischemia. Conclusion: Placental ischemic morphological changes were associated with Doppler ultrasound signs of increased resistance to arterial blood flow, both on the fetal and maternal sides of the placenta. No significant relation to the uterine venous flow velocities was found.     

The effects of ritodrine infusion on fetal myocardial function and fetal hemodynamics

The effects of ritodrine infusion on fetal myocardial function and fetal hemodynamics were studied in 18 singleton, healthy, pregnant women with premature uterine contractions. Ritodrine was given intravenously for 2 1/2 h. In 10 cases both M-mode echocardiographs of the fetal heart and measurements of the blood flow in the fetal descending thoracic aorta were made before and after the infusion. No changes took place in the functional parameters or ventricular size of the fetal heart during the infusion. Fetal heart rate increased significantly. In the aorta both the volumetric flow and time-averaged systolic peak, mean and end-diastolic velocities increased significantly, while there were no changes in wave-form indices. In 8 other cases, blood velocity waveform indices were measured by color Doppler flow mapping from the fetal middle cerebral, renal and umbilical arteries. During the infusion the waveform indices decreased significantly in the middle cerebral and renal arteries. There was no change in the indices of the umbilical artery. Ritodrine did not cause any unfavorable changes in the fetal myocardial function or blood flow in the aorta and umbilical artery. The decreased waveform indices in fetal middle cerebral and renal arteries might indicate decreased vascular resistance in these vessels.     

Umbilical artery flow velocity waveforms and placental resistance: the effects of embolization of the umbilical circulation

Embolization of the umbilical placental circulation in fetal lambs was carried out to occlude the small vessels of the placental vascular bed and to observe the effect on the umbilical artery flow and flow velocity waveforms. Thirteen singleton fetuses were studied from day 120 of pregnancy. Embolization was achieved by injecting approximately 9 X 10(6) microspheres of 15 micron diameter into the fetal placental cotyledons along the umbilical arteries over 9 days. Umbilical and uterine flows were measured by radioactive microsphere counting. The umbilical placental resistance was increased (0.25 to 0.35 mm Hg.ml.min-1) by embolization, and there was an increase in the umbilical artery systolic/diastolic ratio. Embolization produced a significant fall in umbilical flow expressed either as total flow (312 to 237 ml.min-1) or when normalized by reference against splanchnic flow (3.36 to 1.53). We conclude that the umbilical artery flow velocity waveform systolic/diastolic ratio measures the reflection coefficient at the peripheral vascular bed (the "resistance vessels") of the placenta.     

Doppler umbilical and uterine flow waveforms in severe pregnancy hypertension

Summary. Doppler studies of the umbilical and uteroplacental bed arterial flow velocity waveforms were performed in a series of women suffering from severe proteinuric pregnancy hypertension. Ninety-five women were studied and the mean interval between the last study and delivery was 1–4 days. An abnormally elevated umbilical artery systolic:diastolic (AB) ratio was present in 61 (64%) of the women. All 10 perinatal deaths were associated with pregnancies with an abnormal umbilical artery AB ratio. An elevated umbilical artery AB ratio was significantly associated with small-for-gestation and neonatal morbidity. Infants associated with extremely high umbilical artery AB ratios (≥ 99th centile) spent twice as long in the neonatal nursery as those with a lower value. There was no relation between the duration of hypertension and the umbilical study result. The uteroplacental bed artery flow velocity waveform did not correlate with fetal or neonatal mortality or morbidity. Patients with abnormal uteroplacental AB ratios also had abnormal umbilical artery AB ratios. We conclude that an abnormal fetal umbilical artery Doppler flow velocity waveform correlates with adverse fetal outcome in severe proteinuric pregnancy hypertension and suggest that the associated placental lesion may precede the maternal hypertension.