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

OBJECTIVE: To study the power spectrum distribution of heart rate and umbilical artery flow velocity variability in fetuses with increased nuchal translucency thickness (NT). METHODS: 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. RESULTS: 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. CONCLUSION: The autonomic nervous system does not seem to play a role in the altered cardiovascular homeostasis in the presence of increased fetal NT.     

Characteristics of blood flow in intrauterine growth-restricted fetuses with hypercoiled cord.

OBJECTIVE: To clarify the characteristics of fetoplacental blood flow of growth-restricted fetuses with hypercoiled umbilical cord. SUBJECTS: Eight growth-restricted fetuses with hypercoiled cord. METHODS: Flow velocity waveforms of the umbilical cord artery and vein, fetal abdominal aorta and fetal inferior vena cava were analyzed. RESULTS: The resistance index in the umbilical artery in the hypercoiled cases was lower than that in normal fetuses. Early-diastolic reversed flow was observed in the abdominal aorta in some cases. In all cases, umbilical venous pulsation was observed in the entire cord until delivery. In one case, fetal heart failure occurred, resulting in pre-mature delivery. An atrophic type of single umbilical artery was observed in four cases. CONCLUSION: Fetal blood flow disturbance caused by a hypercoiled umbilical cord may be a cause of growth restriction.     

Power spectrum analysis of heart rate and blood flow velocity variability measured in the umbilical and uterine arteries in early pregnancy: a comparative study.

OBJECTIVE: To compare power spectral derived variability parameters from the fetal side of the placental circulation with those from the maternal side of the placental circulation, during early pregnancy. METHODS: Doppler velocity waveforms were obtained from both the umbilical and the uterine arteries in a study group of 40 pregnant women between 10 and 14 (n = 25) and 15 and 20 (n = 15) weeks of gestation. The coefficient of variation of both the beat-to-beat heart rate variability and the blood flow velocity variability was determined. The ratio of the integrated low-frequency components (< 0.2 Hz) and the integrated high-frequency components (> 0.2 Hz) from normalized power spectrum analysis (LH-ratio) was established, to reflect sympathovagal balance. RESULTS: The coefficient of variation and LH-ratio of fetal heart rate variability constitute only a fraction of the same maternal heart rate variability parameters. Nevertheless a highly significant increase (P < 0.001) in LH-ratio was demonstrated with advancing gestational age. The coefficient of variation and LH-ratio of blood flow velocity variability were significantly lower in the fetal umbilical artery only in the 10-14-weeks' gestation group. Due to a decrease of the maternal uterine blood flow velocity variability parameters with advancing gestational age, statistically equal fetal and maternal values for coefficient of variation and LH-ratio were found in the 15-20 weeks' gestation group. CONCLUSIONS: The increase in LH-ratio of fetal heart rate variability indicates functional development of the fetal autonomic nervous system at 15-20 weeks' gestation. The umbilical blood flow velocity variability may be secondary to maternal uterine arterial flow variability rather than due to primary changes in fetal cardiovascular function.     

Umbilical cord morphologic characteristics and umbilical artery Doppler parameters in intrauterine growth-restricted fetuses.

OBJECTIVE: To compare prenatal morphometric changes of umbilical cord components in intrauterine growth-restricted fetuses with and without abnormal umbilical artery Doppler parameters. METHODS: Consecutive singleton intrauterine growth-restricted fetuses at a gestational age of older than 20 weeks were compared with matched appropriate-for-gestational-age fetuses. Intrauterine growth restriction was defined in the presence of a sonographic abdominal circumference below the 5th percentile for gestational age at the time of sonography and a birth weight below the 10th percentile. The sonographic examination included pulsed Doppler measurements of the umbilical artery resistance index and measurements of the umbilical cord cross-sectional area and the umbilical cord vessel area. RESULTS: A total of 84 intrauterine growth-restricted fetuses and 168 appropriate-for-gestational-age fetuses were included in the study. All umbilical cord components (umbilical cord cross-sectional area, vein area, artery area, and Wharton jelly area) were smaller in the intrauterine growth-restricted fetuses. The prevalence of lean umbilical cords (cross-sectional area < 10th percentile for gestational age) was significantly higher in intrauterine growth-restricted fetuses compared with appropriate-for-gestational-age fetuses (73.8% versus 11.3%; P < .0001). A significant and progressive reduction of the umbilical vein area corresponding to the degree of umbilical artery Doppler parameter abnormality was found. The umbilical artery area was not related to the hemodynamic changes of the blood flow in the umbilical arteries. CONCLUSIONS: The proportion of lean umbilical cords was higher in intrauterine growth-restricted fetuses than in appropriate-for-gestational-age fetuses. Umbilical vein caliber decreases significantly with worsening of umbilical artery Doppler parameters.     

Fetal heart rate and umbilical artery velocity variability in fetuses with congenital cardiac defects: a preliminary study.

OBJECTIVE: To examine whether variabilities in fetal heart rate and umbilical artery flow velocity are possible markers for hemodynamic dysfunction in fetuses with a congenital heart defect. METHODS: Doppler studies of the umbilical artery velocity waveform were performed at 20-35 weeks of gestation in 13 patients with a congenital heart defect. We determined absolute and variability values for heart rate and flow velocities from umbilical artery velocity waveforms of at least 18 s duration. We compared these findings with normal controls matched for gestational age. RESULTS: Fetuses with a congenital heart defect displayed decreased umbilical artery peak systolic and time-averaged velocities. However, variability in peak systolic and time-averaged velocities and fetal heart rate variability were increased compared with normal controls. Absolute fetal heart rates were similar between the two groups. CONCLUSIONS: Marked cardiovascular changes occur in the fetus with a congenital heart defect compared with the normal healthy fetus. We propose that variability in fetal heart rate and umbilical artery blood flow velocity could be additional markers for impaired homeostasis in the presence of fetal congenital heart disease.     

Umbilical vein blood flow in growth-restricted fetuses.

OBJECTIVE: To determine whether umbilical blood flow is reduced in a subset of growth-restricted (IUGR) fetuses when expressed as flow per kilogram or flow per unit of specific sonographic fetal measurements. DESIGN: Prospective. SUBJECTS: Thirty-seven IUGR fetuses were examined by Doppler ultrasound within 4 h of the last non-stress test prior to delivery. This population was divided into three groups of varying clinical severity according to the characteristics of umbilical arterial pulsatility index (PI) and heart rate. METHODS: Absolute and weight-specific umbilical vein (UV) flow were calculated from measurements of UV diameter and UV mean velocity. Umbilical vein diameter, velocity and UV flow were calculated also per unit head (HC) or abdominal circumference (AC) and correlated with gestational age. RESULTS: Umbilical vein flow (UVf) per kilogram fetal weight was significantly lower in the more severe IUGR fetuses (abnormal umbilical arterial PI) than in normally grown comparable fetuses (P < 0.001). Umbilical vein flow per unit HC was significantly lower in the three groups (P < 0.001) than in the control population. The UV diameter/HC ratio was normal whereas UV velocity/HC ratio was significantly lower in IUGR fetuses than in comparable controls. CONCLUSIONS: The present study clearly establishes that umbilical venous blood flow is reduced in IUGR fetuses on a weight-specific basis. The sonographic growth parameter which best distinguishes umbilical flow differences of IUGR fetuses from normal fetuses is the head circumference.     

Longitudinal changes in the ductus venosus, cerebral transverse sinus and cardiotocogram in fetal growth restriction.

OBJECTIVE: To evaluate the changes in flow velocity waveforms in the transverse cerebral sinus in growth-restricted fetuses and to correlate these changes with (1) flow velocity waveforms in the ductus venosus and (2) changes in computerized analysis of the fetal cardiotocogram. DESIGN: Fetuses between 22 and 37 weeks' gestation with an estimated fetal weight below the fifth centile were included in this prospective longitudinal study. Doppler measurements of the umbilical artery, descending aorta, middle cerebral artery, transverse cerebral sinus and ductus venosus were recorded. Fetal heart rate was analyzed by a computer system according to the Dawes-Redman criteria. RESULTS: We measured a significant correlation between pulsatility index in the cerebral transverse sinus and in the ductus venosus over the study period and at delivery. There was a negative correlation between these indices and short- and long-term variability of the fetal heart rate. There was a parallel increase in pulsatility in the ductus venosus and the transverse cerebral sinus. These changes were inversely correlated with fetal heart rate variability and preceded fetal distress. CONCLUSION: Cerebral venous blood flow in IUGR fetuses may be a useful additional investigation to discriminate between fetal adaptation and fetal decompensation in chronic hypoxemia.     

Staging of intrauterine growth-restricted fetuses.

OBJECTIVE: The purpose of this study was to evaluate the value of cardiovascular, ultrasonographic, and clinical parameters for developing a staging classification of intrauterine growth-restricted (IUGR) fetuses delivered at 32 weeks or earlier. METHODS: Intrauterine growth restriction was defined as the presence of an estimated fetal weight below the 10th percentile. Intrauterine growth-restricted fetuses were staged according to the following parameters, with the presence of any 1 parameter in a stage placing the fetus in that stage: stage I, an abnormal umbilical artery or middle cerebral artery pulsatility index; stage II, an abnormal middle cerebral artery peak systolic velocity, umbilical artery absent/reversed diastolic flow, umbilical vein pulsation and an abnormal ductus venosus pulsatility index; and stage III, reversed flow at the ductus venosus or reversed flow at the umbilical vein, an abnormal tricuspid E wave (early ventricular filling)/A wave (late ventricular filling) ratio, and tricuspid regurgitation. Each stage was divided into A (amniotic fluid index [AFI] <5 cm) and B (AFI >5 cm). The presence of maternal abnormalities was also reported. RESULTS: Seventy-four IUGR fetuses delivered at 32 weeks or earlier were included. Gestational age at delivery was greater in stage I fetuses compared with the other stages. Birth weight decreased with advancing stages. Stage III fetuses had the lowest AFI. There was a direct correlation between the severity of staging and both perinatal mortality and mortality occurring between 20 weeks' gestation and before the neonates were discharged from the hospital (P < .05). CONCLUSIONS: The staging system proposed here may allow comparison of outcome data for IUGR fetuses and may be valuable in determining more timely delivery for these high-risk fetuses.     

Fetal adrenal artery velocimetry measurements in appropriate-for-gestational age and intrauterine growth-restricted fetuses.

OBJECTIVE: To investigate adrenal artery blood flow in the fetus. DESIGN AND METHOD: Sixty-two appropriate-for-gestational-age (AGA) and 20 intrauterine growth-restricted (IUGR) fetuses were recruited to this cross-sectional study between 22 and 42 weeks of pregnancy in a tertiary referral fetal medicine unit of a university hospital. ENDPOINTS: Doppler velocimetry of the fetal adrenal, umbilical (UA), renal and middle cerebral arteries (MCA). Pulsatility index (PI), resistance index (RI), peak systolic velocity (PSV), time-averaged maximum velocity (TAMXV) and cerebroplacental ratio (MCA RI/UA RI; CPR). Obstetric outcome. RESULTS: The adrenal artery was detected in 82% of the fetuses. All flow velocity waveforms obtained from the adrenal artery indicated low impedance blood flow. No significant changes in PI, RI, PSV and TAMXV occurred with advancing gestation. The blood flow parameters of the adrenal artery did not differ between AGA and IUGR fetuses. In five IUGR fetuses with signs of redistribution of cardiac output in favor of the brain, the adrenal artery velocimetry results were unremarkable. The adrenal artery PI, RI, PSV and TAMXV values were higher in female fetuses than in male fetuses (P < 0.05). A relationship was observed between the velocity measurements and the estimated fetal weight (P < 0.01). CONCLUSIONS: The fetal adrenal artery could be readily detected. We observed no redistribution of blood flow in favor of the fetal adrenals in IUGR fetuses which were not severely compromised.     

Assessment of fetal heart rate variability and velocity variability by Doppler velocimetry of the descending aorta at 10-20 weeks of gestation.

OBJECTIVES: Determination of gestational age-related modulations in fetal heart rate and descending aorta blood flow velocity in the early human fetus and comparison of aortic variability data with data obtained from the umbilical artery. It is hypothesized that these modulations present in the umbilical artery also occur in the descending aorta. METHODS: Doppler studies of descending aorta velocity waveforms were performed at 10-20 weeks in 55 normal pregnant women. In 24 of the 55 women, Doppler recordings from both the descending aorta and the umbilical artery were collected. Absolute values and variability of fetal heart rate, peak systolic and time-averaged velocities were determined from flow velocity waveforms of at least 18 s in duration. RESULTS: From 10 to 20 weeks of gestation, the descending aorta peak systolic and time-averaged velocities increased, whereas the fetal heart rate decreased. The descending aorta peak systolic variability also increased. However, the time-averaged velocity variability and fetal heart rate variability remained constant during the study period. In the subset of 24 women, the fetal heart rate variability and velocity variability data from the descending aorta and umbilical artery were not significantly different. CONCLUSIONS: Reproducible fetal heart rate and velocity variability data can be derived from the descending aorta and umbilical artery. The increase in heart rate variability observed in the umbilical artery was not seen in recordings obtained from the descending aorta. Different fetal activity states may be the underlying mechanism for these heart rate variability discrepancies.     

Fetal heart rate and umbilical artery velocity variability in pregnancies complicated by insulin-dependent diabetes mellitus.

OBJECTIVES: To examine the variability in fetal heart rate and absolute flow velocity, which are possible hemodynamic markers of cardiovascular homeostasis in pregnancies complicated by diabetes mellitus. METHODS: Doppler studies of umbilical artery velocity waveforms were performed at 12-21 weeks of gestation in 16 women with well-controlled type I (insulin-dependent) diabetes mellitus. From umbilical artery velocity waveforms of at least 13 s in duration, we determined absolute values and beat-to-beat variability for fetal heart rate and umbilical artery flow velocities and compared these findings with normal controls matched for gestational age. RESULTS: Fetuses of diabetic women displayed increased fetal heart rate variability and umbilical artery peak systolic velocity. Fetal heart rate, umbilical artery time-averaged velocity and variability in umbilical artery flow velocity were not essentially different between the two groups. CONCLUSION: Fetal heart rate variability and umbilical artery peak systolic velocity may be markers for fetal cardiovascular homeostasis in pregnancies complicated by insulin-dependent diabetes mellitus.     

Umbilical venous volume flow in the normally developing and growth-restricted human fetus.

OBJECTIVE: To determine the reproducibility of measurement of umbilical venous volume flow components and to calculate umbilical venous volume flow in normal and growth-restricted (small-for-gestational age) fetuses in a cross-sectional study. METHOD: Using Labview and Imaq-vision software, the cross-sectional inner area of the umbilical vein was traced. Vessel area (mm2) and Doppler-derived time-averaged flow velocity (mm/s) were multiplied to calculate volume flow (mL/min) including flow per kg fetal weight. The coefficient of variation for vessel area and flow velocity scans and tracings were determined (n = 13; 26-35 weeks). Normal charts for components and volume flow were constructed (n = 100; 20-36 weeks) and related to data from growth restricted fetuses (birth weight < 5th centile) (n = 33; 22-36 weeks). In growth-restricted fetuses the umbilical artery pulsatility index was also obtained. RESULTS: Reproducibility: The coefficient of variation was 5.4% (vessel area) and 7.3% (time-averaged velocity) for scans and 6.6% and 10.5% for measurements, resulting in a coefficient of variation of 8.1% (scans) and 11.9% (measurements) for volume flow. A gestational age-related increase exists for vessel area, time-averaged flow velocity and umbilical venous volume flow from 33.2 (SD, 15.2) mL/min at 20 weeks to 221.0 (SD, 32.8) mL/min at 36 weeks of gestation, but there is a reduction from 117.5 (SD, 33.6) mL/min to 78.3 (SD, 12.4) mL/min for volume flow per kg fetal weight. In small-for-gestational age fetuses, the values were below the normal range in 31 of 33 cases for volume flow and in 21 of 33 cases for volume flow per kg fetal weight. Umbilical artery pulsatility index was significantly different between the subsets with normal and those with reduced volume flow per kg fetal weight. CONCLUSIONS: Measurements of umbilical venous vessel area and time-averaged velocity resulted in acceptable reproducibility of volume flow calculations, which show a seven-fold increase at 20-36 weeks of gestation. In growth-restricted fetuses, volume flow is significantly reduced. When calculated per kg/fetus, the values were reduced in 21 (63.6%) out of 33 cases.     

Antenatal prediction of intraventricular hemorrhage in fetal growth restriction: what is the role of Doppler?

OBJECTIVE: To evaluate relationships between neonatal intraventricular hemorrhage and altered brain blood flow in preterm growth-restricted fetuses. METHODS: One hundred and thirteen growth-restricted fetuses (birth weight < 10th centile and umbilical artery pulsatility index > two standard deviations above gestational age mean) which delivered prematurely (< 34.0 weeks) were studied. Three expressions of altered brain blood flow were defined: 'brain sparing'= middle cerebral artery pulsatility index > two standard deviations below the gestational age mean, 'centralization' = ratio of middle cerebral artery/umbilical artery pulsatility indices (cerebroplacental ratio) > two standard deviations below the gestational age mean, and 'redistribution' = absent or reversed umbilical artery end-diastolic velocity. Intraventricular hemorrhage was graded after Papile (I-IV) by cranial ultrasound performed within 7 days of delivery. RESULTS: Sixty-seven (59.3%) fetuses had brain sparing, 84 (74.3%) had centralization and 51 (45.1%) had redistribution. Fifteen (13.3%) neonates had intraventricular hemorrhage and were more likely to have a biophysical profile < 6, earlier delivery for fetal indications, lower cord artery pH, HCO3, hemoglobin, and platelets, a 10-min Apgar score < 7 and high perinatal mortality (5/15; 33.3%). No associations between intraventricular hemorrhage and brain sparing or centralization were identified. However, neonates with intraventricular hemorrhage had significantly higher umbilical artery pulsatility index deviations from the gestational age mean and a relative risk of 4.9-fold for intraventricular hemorrhage with redistribution (95% confidence interval, 1.5-16.3; P < 0.005). Multiple logistic regression revealed significant associations between intraventricular hemorrhage and a low 10-min Apgar score (r = 0.30, P < 0.005) and low hemoglobin (r = 0.28), gestational age at delivery (r = 0.25) and birth-weight centiles (r = 0.23) (P < 0.05). No Doppler parameter was identified as an independent contributor to intraventricular hemorrhage. CONCLUSION: While loss of umbilical artery end-diastolic velocity early in gestation significantly increases the risk for neonatal intraventricular hemorrhage, prematurity and difficult transition to extrauterine life remain the most important determinants of intraventricular hemorrhage.     

Temporal sequence of abnormal Doppler changes in the peripheral and central circulatory systems of the severely growth-restricted fetus.

OBJECTIVE: To identify the temporal sequence of abnormal Doppler changes in the fetal circulation in a subset of early and severely growth-restricted fetuses. METHODS: This was a prospective observational study in a tertiary care/teaching hospital. Twenty-six women who were diagnosed with growth-restricted fetuses by local standards before 32 weeks' gestation and who had abnormal uterine and umbilical artery Doppler velocimetry were enrolled onto the study. To compare Doppler changes as a function of time, pulsed-wave Doppler ultrasound was performed on five vessels in the fetal peripheral and central circulations. Doppler examinations were performed twice-weekly and on the day of delivery if the fetal heart rate tracing became abnormal. Doppler indices were scored as abnormal when their values were outside the local reference limits on two or more consecutive measurements. Biometry for assessment of fetal growth was performed every 2 weeks. Computerized fetal heart rates were obtained daily. Delivery was based on a non-reactive fetal heart rate tracing and not on Doppler information. Patients with a severely growth-restricted fetus who were delivered for maternal indications such as pre-eclampsia were excluded. Perinatal outcome endpoints included: intrauterine death, gestational age at delivery, newborn weight, central nervous system damage of grade 2 or greater, intraventricular hemorrhage and neonatal mortality. RESULTS: Mean gestational age and newborn weight at delivery were 29 (standard deviation (SD), 2) weeks and 818 (SD, 150) g, respectively. The sequence of Doppler velocimetric changes was described by onset time cumulative curves that showed two time-related events. First, for each vessel there was a progressive increase in the percent of fetuses developing a Doppler abnormality. Second, severely growth-restricted fetuses followed a progressive sequence of acquiring Doppler abnormalities which were categorized into 'early' and 'late' Doppler changes. Early changes occurred in peripheral vessels (umbilical and middle cerebral arteries; 50% of patients affected 15-16 days prior to delivery). Late changes included umbilical artery reverse flow, and abnormal changes in the ductus venosus, aortic and pulmonary outflow tracts (50% of patients affected 4-5 days prior to delivery). The time interval between the occurrence of early and late changes was significantly different (P < 0.0001) and late changes were significantly associated with perinatal death (P < 0.01). CONCLUSIONS: Doppler velocimetry abnormalities develop in different vessels of the severely growth-restricted fetus in a sequential fashion. Late changes in vascular adaptation by the severely growth-restricted fetus are the best predictor of perinatal death.     

Do heart rate and velocity variability derived from umbilical artery velocity waveforms change prior to clinical pregnancy-induced hypertension?

OBJECTIVE: To investigate the hypothesis that alterations in heart rate variability, peak systolic velocity variability and time-averaged velocity variability in the human umbilical artery may predict early signs of dysfunctional fetal-placental coupling in pregnancies that later develop pregnancy-induced hypertension. METHODS: Doppler flow velocity recordings from the umbilical artery were performed at 10-20 weeks of gestation in 12 nulliparous women who subsequently developed pregnancy-induced hypertension. From umbilical artery velocity waveforms of at least 12 s in duration we determined absolute values and beat-to-beat variability in fetal heart rate, peak systolic and time-averaged velocity and compared these findings with those in normal nulliparous pregnant women matched for gestational age. RESULTS: Absolute values for fetal heart rate, peak systolic and time-averaged velocity as well as beat-to-beat variability in fetal heart rate did not differ significantly between women later developing pregnancy-induced hypertension and normal controls. However, variability in peak systolic velocity and time-averaged velocity were decreased in women who subsequently developed pregnancy-induced hypertension. CONCLUSIONS: Whereas fetal heart rate variability was similar, umbilical artery flow velocity variability was reduced in women developing pregnancy-induced hypertension compared with controls. It is proposed from this study that variability of the umbilical artery flow velocity is associated with mechanical changes in the vascular bed of women who later develop pregnancy-induced hypertension.     

New Doppler index for prediction of perinatal brain damage in growth-restricted and hypoxic fetuses.

OBJECTIVE: To evaluate the new vascular score, hypoxia index (HI), in the prediction of sonographically detected structural brain lesions in neonates within the first week after delivery of growth-restricted fetuses. METHODS: This prospective study included 29 growth-restricted fetuses delivered between 31 and 40 gestational weeks. Doppler umbilical artery (UA) and middle cerebral artery (MCA) resistance indices (RI) were recorded at 48-h intervals for at least 2 weeks before delivery. The cerebroumbilical ratio (C/U ratio = MCA-RI/UA-RI) and the HI (the sum of the daily reductions in C/U ratio, i.e. percentage below the cut-off value of 1, over the period of observation) were calculated. After delivery, neonatal outcome was evaluated according to obstetric parameters and ultrasound examinations of the brain. Doppler indices, C/U ratio and HI, as well as neonatal clinical and biochemical parameters, were tested as potential predictors of brain lesions using the C4.5 data-mining algorithm. RESULTS: Neonatal brain lesions were detected in 13 growth-restricted fetuses. Of all the parameters tested by the C4.5 data-mining algorithm, only HI was identified as a predictor of neonatal brain lesions. HI also showed better correlation with neonatal biochemical parameters, such as umbilical venous partial pressure of oxygen and umbilical venous pH, compared with the C/U ratio. CONCLUSIONS: HI, which takes into account cumulative oxygen deficit, could significantly improve the prediction of a poor neurological outcome in pregnancies complicated by growth restriction and hypoxia.     

Ductus venosus shunting in growth-restricted fetuses and the effect of umbilical circulatory compromise.

OBJECTIVE: To determine the degree of ductus venosus (DV) shunting in fetuses with intrauterine growth restriction (IUGR) and the effect of various degrees of umbilical circulatory compromise. METHODS: This was a cross-sectional observational study. Sixty-four fetuses with IUGR (estimated weight < or = 2.5(th) percentile) underwent ultrasound examination. The diameter, velocity, and blood flow were determined in the DV and intra-abdominal umbilical vein (UV), and the fraction of shunting and DV : UV diameter ratios were calculated. Placental compromise was classified according to either normal umbilical artery (UA) pulsatility index (PI), UA-PI > 97.5(th) percentile, or absent or reversed end-diastolic flow velocity (A/REDV). Regression analysis was used to construct mean values, and SD scores were used to determine differences compared with a reference population (n = 212) after ln- or power-transformation. RESULTS: In the 64 growth-restricted fetuses, the average DV shunting was 39% compared with 25% in the reference group (overall P < 0.0001). The corresponding values in the subgroups with normal UA-PI, UA-PI > 97.5(th) percentile, and A/REDV were 31%, 35%, and 57%, respectively. Fetuses with IUGR and normal UA-PI (SD score: mean, 0.48; 95% CI, 0.04-0.92) did not shunt significantly more than did the reference fetuses (SD score: mean, 0.0; 95% CI, - 0.15 to 0.15), but those with UA-PI > 97.5(th) percentile (SD score: mean, 0.85; 95% CI, 0.41-1.29), and particularly those with A/REDV (SD score: mean, 1.56; 95% CI, 1.0-2.12) did shunt significantly more. With more DV shunting, these fetuses distributed correspondingly less umbilical blood to the liver, one of the mechanisms being a lower perfusion pressure as reflected in the lower DV blood velocity (P < 0.0001). CONCLUSIONS: DV shunting is higher and the umbilical blood flow to the liver is less in fetuses with IUGR, particularly in those with the most severe umbilical hemodynamic compromise.     

Combination of fetal Doppler velocimetric resistance values predict acidemic growth-restricted neonates.

OBJECTIVE: This study was undertaken to determine the efficacy of combination Doppler velocimetric resistance values of the umbilical artery and ductus venosus in predicting growth-restricted neonates with acidemia. METHODS: This retrospective case-control study included 61 gravidas complicated by intrauterine growth restriction with acidemia and 65 control pregnancies. The Doppler velocimetric resistance values obtained from the growth-restricted and control fetuses were in turn compared with the median values derived from another 192 normal pregnancies to adjust the biometric bias due to gestational age. RESULTS: Based on the pulsatility index of the umbilical artery and pulsatility index for the vein of the ductus venosus, the areas under the receiver operating characteristic curves were 0.7992 and 0.6749, respectively, for predicting growth-restricted neonates with acidemia. With a combination of the pulsatility indices of the umbilical artery and the pulsatility indices for the vein of the ductus venosus, the predictive accuracy of the growth-restricted neonates with acidemia increased, with sensitivity of 0.79 and specificity of 0.79 and an area under the receiver operating characteristic curve of 0.8441. CONCLUSIONS: Compared with single-vessel assessment, combining the pulsatility indices of the umbilical artery and the pulsatility indices for the vein of the ductus venosus provides the greatest accuracy in predicting growth-restricted neonates with acidemia.     

Central arterial hemodynamics in small-for-gestational-age fetuses before and during maternal hyperoxygenation: a Doppler velocimetric study with particular attention to the aortic isthmus.

OBJECTIVE: Hemodynamic changes indicating a normalization of fetal blood flow redistribution during maternal oxygen administration have been suggested to be of positive prognostic value in growth-restricted fetuses. The aortic isthmus has been suggested as a site for early detection of blood flow redistribution as well as for verification of a response to maternal hyperoxygenation. The present study was performed to investigate whether this concept could be confirmed in a study involving fetuses assumed to have only a moderate disturbance in fetoplacental hemodynamics. DESIGN AND SUBJECTS: Twenty-five singleton fetuses with an estimated weight less than -2 SD below the gestational age-related mean and without any malformation or chromosomal aberration were studied between 27 and 38 (median 34) weeks of gestation. METHODS: Velocity waveforms from the mitral valve, aortic valve, middle cerebral artery, aortic isthmus and umbilical artery were recorded before and during maternal breathing of 100% oxygen. RESULTS: Nine fetuses demonstrated absent or reversed end-diastolic velocity (ARED) in the aortic isthmus while forward flow was present in the umbilical artery. The cerebral artery pulsatility index (PI) increased with oxygen administration and there was a decrease in the aortic isthmus PI. Variables obtained from the other recording sites did not change with maternal hyperoxygenation. CONCLUSIONS: ARED in the aortic isthmus appears to be an early sign of blood flow redistribution in this group of fetuses. Maternal oxygenation results in velocity waveform changes that suggest an increase of cerebral vascular resistance and a redistribution of blood from the brain to the vascular beds supplied by the descending aorta. The aortic isthmus is a suitable site to verify this response.     

Qualitative venous Doppler waveform analysis improves prediction of critical perinatal outcomes in premature growth-restricted fetuses.

BACKGROUND: Our aim was to test the hypothesis that qualitative ductus venosus and umbilical venous Doppler analysis improves prediction of critical perinatal outcomes in preterm growth-restricted fetuses with abnormal placental function. METHODS: Patients with suspected intrauterine growth restriction (IUGR) underwent uniform fetal assessment including umbilical artery (UA), ductus venosus (DV) and umbilical vein (UV) Doppler. Absent or reversed UA end-diastolic velocity (UA-AREDV), absence or reversal of atrial systolic blood flow velocity in the DV (DV-RAV) and pulsatile flow in the umbilical vein (P-UV) were examined for their efficacy to predict critical outcomes (stillbirth, neonatal death, perinatal death, acidemia and birth asphyxia) before 37 weeks' gestation. RESULTS: Seventeen (7.6%) stillbirths and 16 (7.1%) neonatal deaths were observed among 224 IUGR fetuses. Forty-one neonates were acidemic (19.8%) and seven (3.1%) had birth asphyxia. Logistic regression showed that UA-AREDV had the strongest association with perinatal mortality (R(2) = 0.49, P < 0.001), stillbirth (R(2) = 0.48, P < 0.001) and acidemia (R(2) = 0.22, P = 0.002) while neonatal death was most strongly related to DV-RAV and P-UV (R(2) = 0.33, P = 0.007). UA waveform analysis offered the highest sensitivity and negative predictive value and DV-RAV and P-UV had the best specificity and positive predictive values for outcome prediction. Overall, DV-RAV or P-UV offered the best prediction of acidemia and neonatal and perinatal death irrespective of the UA waveform. In fetuses with UA-AREDV, prediction of asphyxia and stillbirth was significantly enhanced by venous Doppler. CONCLUSION: Prediction of critical perinatal outcomes is improved when venous and umbilical artery qualitative waveform analysis is combined. The incorporation of venous Doppler into fetal surveillance is therefore strongly suggested for all preterm IUGR fetuses.