Reproducibility of ductus venosus Doppler flow measurements at 11-14 weeks of gestation

Inter- and intra-observer variability in fetal ductus venosus blood flow measurements in high-risk fetuses at 26-32 weeks

OBJECTIVES

Early preterm fetal growth restriction is a significant contributor to perinatal morbidity and mortality. The ductus venosus pulsatility index for veins (DV PIV) is proposed as a monitoring tool because it appears to improve perinatal outcomes. The test characteristics and robustness of DV PIV have been inadequately described. The aim of this study was to investigate inter- and intra-observer variability of DV PIV.

STUDY DESIGN

Nineteen women with a gestational age between 26 and 32 completed weeks were included in this study. Doppler sonographic fetal assessment was performed by two independent maternal-fetal medicine specialists. Each sonographer alternately performed three flow tracings for each participant, in the absence of the other sonographer (six tracings in total per patient). DV PIV was calculated automatically from stored tracings by a third researcher. Inter- and intra-observer variability of DV PIV and limits of agreement were assessed using the Bland-Altman method. Comparison of the distribution was performed with Kendall's related samples test, and the intraclass correlation coefficient (ICC) was calculated.

RESULTS

In total, 114 DV measurements were taken from 19 participants with a median age of 31 years [interquartile range (IQR) 26-34 years] at a median gestational age of 28 weeks (IQR 27-29 weeks). The proportional limits of agreement for intra-observer variation were -0.48 to 0.48 and -0.39 to 0.62 for the two observers. ICCs were 0.66 [95% confidence interval (CI) 0.42-0.84] and 0.68 (95% CI 0.45-0.85). The proportional limits of agreement for inter-observer variation were -0.29 to 0.19 with an ICC of 0.89 (95% CI 0.73-0.96).

CONCLUSION

Inter-observer variation was far less than intra-observer variation, probably due to mitigation of biological variation by averaging three measurements. DV PIV has acceptable test characteristics for use in a clinical setting when the average of at least three consecutive measurements is used.

Normal reference ranges of ductus venosus Doppler indices in the period from 14 to 40 weeks' gestation

OBJECTIVE

To construct reference ranges of ductus venosus (DV) Doppler indices in normal singleton pregnancies.

METHODS

A cross-sectional study was conducted on low-risk singleton pregnancies with accurate gestational age, and normal fetuses were enrolled into the study. Measurements of DV Doppler indices were determined by experienced sonographers. Poor quality images were excluded.

RESULTS

A total of 640 fetuses underwent DV measurements, ranging from 13 to 30 for each gestational week. The relationship between gestational age and DV Doppler indices was not linear. The best-fit regression equations are as follows: preload index = (5.061 - 0.4882) × exp (-0.211 × GA) + 0.4882; peak velocity index for veins = (7.498 - 0.5609) × exp (-0.2184 × GA) + 0.5609; pulsatility index for veins = (17.9 - 0.6053) × exp (-0.2512 × GA) + 0.6053; systolic/atrial wave ratio = (300 - 2.124) × exp (-0.3649 × GA) + 2.124. Notably, during the period from 14 to 20 weeks' gestation, all of the four indices rapidly decreased and they were relatively stable or slightly decreased after that. The nomogram tables for various percentile ranges were constructed.

CONCLUSION

A nomogram for DV Doppler indices for each gestational week during the period from 14 to 40 weeks' gestation was established. These reference ranges may be a useful non-invasive tool for evaluation of fetal cardiac function.

Ductus Venosus: A Love Story of 14 Years

Ductus venosus is a tiny vessel with a central role in fetal circulation. Combining B-mode with color and pulsed Doppler is feasible to identify this vessel and evaluate the blood flow waveform at 11 to 13 weeks. The higher prevalence of abnormal A-wave in fetuses with abnormal karyotype and/or cardiac defects turned DV evaluation into a useful marker for chromosomal abnormalities and cardiopathies. Even when combined with nuchal translucency (NT) or biochemical markers, DV blood flow evaluation contributes to an increase in sensitivity and reduces false-positive rate. Abnormal ductal flow is also related to a worse fetal and perinatal outcome. In monochorionic twin pregnancies, in addition to NT measurement at 11 to 14 weeks, the Doppler assessment of DV blood flow increases relevantly the performance of screening for those at higher risk of developing twin-to-twin transfusion syndrome. This story of 14 years surely contributed to change the way first trimester screening is being implemented.

Ductus venosus pulsatility index measurement reduces the false-positive rate in first-trimester screening

OBJECTIVE

To investigate if ductus venosus (DV) pulsatility index for veins (PIV) and a-wave measurements can increase the accuracy of first-trimester Down syndrome screening in a high-risk population.

METHODS

The database of our fetal medicine unit was searched for all cases at increased first-trimester Down syndrome risk. Multivariable logistic regression was used to construct a prediction rule for chromosomal anomalies at any given maternal age, nuchal translucency multiples of the median (NT-MoM) and DV-PIV MoM. The discriminative ability of the model was assessed by using receiver-operating characteristics (ROC) analysis.

RESULTS

The study population included 445 fetuses. DV-PIV was increased (≥ 95(th) percentile) in 239 (54%) and DV a-wave was abnormal in 187 fetuses (42%). In this cohort, 80% of all chromosomal anomalies were identified by an increased DV-PIV and 68% by an abnormal a-wave. The odds of chromosomal anomalies increased by a factor of 4.2 per MoM increase in DV-PIV, adjusted for NT and maternal age. The area under the ROC curve for the prediction of chromosomal anomalies was 0.79. After correction for DV-PIV, DV a-wave did not significantly add to the prediction of chromosomal anomalies.

CONCLUSION

In a population of fetuses at increased first-trimester risk for Down syndrome, the combination in a logistic regression model of NT, DV-PIV and maternal age can improve the accuracy of screening for trisomy 21 and other chromosomal anomalies. This is the first study that models the additional value of DV-PIV as a continuous variable to NT measurement alone in a high-risk first-trimester population.

Reproducibility and repeatability of measuring the electrical impedance of the pregnant human cervix-the effect of probe size and applied pressure

Background

The utility of cervical electrical impedance spectroscopy (EIS) as a diagnostic tool is being investigated in clinical trials. We sought to assess the reliability of two different sizes of tetrapolar probes used in measuring cervical impedance.

Methods

Cervical transfer impedance was measured at 14 frequencies between 76 and 625 000 Hz from 11 pregnant subjects at term. Repeated measurements were taken with two probes (3 mm and 12 mm diameter) applied softly (approximately 0.7 Newton of force), and firmly (approximately 2.2 Newton) to the surface of the cervix by two observers. The intra-class correlation coefficient (ICC), coefficient of variation (CV) and repeatability standard deviations (SD) were derived from these measurements and compared.

Results

Measurements taken by one observer were highly repeatable for both probes as demonstrated by high ICC and low CV values. Probe performance was improved further by firm application. Firm application of the 3 mm probe resulted in ICC values that ranged from 0.936 to 0.986 (p = 0.0001) and CV values between 1.0 and 3.4%. Firm pressure with the 12 mm probe resulted in ICC values that ranged between 0.914 and 0.988 (p = 0.0001) with CV values between 0.7 and 2.1%. In addition, the repeatability SD was low across all frequencies implying that there was low intra-observer variability. Measurements taken by 2 observers with firm application of the 12 mm probe demonstrated moderate reproducibility between 9.8 and 156 kHz, the frequency range in which previous clinical studies have shown predictive association between high cervical resistivity and vaginal delivery: ICC values ranged between 0.528 and 0.638 (p < 0.05), CV values were between 3.3 and 5.2% and reproducibility SD values were also low. In contrast the 3 mm probe demonstrated poor reproducibility at all study frequencies.

Conclusion

Measuring cervical resistivity by a single observer with both the 3 and 12 mm probes is highly repeatable whilst inter-observer reproducibility is poor with the 3 mm probe but moderately good when the 12 mm probe is firmly applied to the cervix in the frequency range 9.8 to 156 kHz, consistent with our observations of probe performance in clinical trials.

Reliability of fetal middle cerebral artery velocity measurements: a randomized controlled trial of sonographer training

OBJECTIVE

The purpose of this study was to determine the reliability of fetal middle cerebral artery (MCA) peak systolic velocity (PSV) measurements at a tertiary care center and to evaluate the effect of targeted training for sonographers.

METHODS

Six sonographers were randomized to training modules for fetal MCA PSV or amniotic fluid volume (AFV) measurements. Six fetuses of uncomplicated pregnancies were selected for participation. Middle cerebral artery and AFV measurements were obtained before and after a training module. The intraobserver and interobserver variability (reliability) was calculated with intraclass correlation coefficients and was compared between groups.

RESULTS

Administration of the MCA training module increased the number of technically adequate MCA images obtained (odds ratio, 3.95; 95% confidence interval, 1.07-14.65). The intraobserver and inter-observer variability for MCA measurements was significantly reduced after the targeted training module (P = .05).

CONCLUSIONS

The reliability of fetal MCA PSV measurements improved after a targeted training program.

Reliability analysis on ductus venosus assessment at 11–14 weeks' gestation in a high-risk population

OBJECTIVE

To assess the intra- and interobserver reliability of the fetal ductus venosus (DV) blood flow measurements at 11-14 weeks' gestation in a high-risk population for chromosomal defects.

METHODS

Thirty-five consecutive singleton pregnancies at high risk for chromosomal or genetic anomalies were included. DV end-diastolic velocity (EDV) and the pulsatility index for veins (PIV) were determined by manual tracing in three sets of waveforms by a single sonographist to assess intraobserver reliability using transvaginal ultrasound. Subsequently, the EDV and the PIV were also determined in a further set by a second sonographist to assess interobserver reliability. Reliability was evaluated by means of the Intraclass Correlation Coefficient (ICC). The degree of agreement was also examined using the limits of agreement method.

RESULTS

The intraobserver reliability was 0.81 (95% C.I. 0.69-0.89) for EDV and 0.91 (95% C.I. 0.85-0.95) for the PIV, both corresponding to almost perfect reliability. The interobserver reliability was 0.50 (95% C.I. 0.20-0.70) for EDV, and 0.74 (95% C.I. 0.54-0.86) for PIV, corresponding respectively to moderate and substantial reliabilities. The 95% interval of the EDV differences (cm/s) within and between observers were (+6.1, - 4.6) and (+13.6, - 9.7), respectively. The 95% interval of the PIV differences within and between observers were (+0.32, - 0.36) and (+0.7, - 0.67), respectively.

CONCLUSIONS

Interobserver reliability for EDV is only moderate, whereas for the PIV is substantial, allowing its use for clinical purposes in a high-risk population.

First-trimester ductus venosus, nasal bones, and Down syndrome in a high-risk population

OBJECTIVE

Assessing the role of fetal ductus venosus and nasal bones evaluation in first-trimester screening for Down syndrome.

METHODS

This was a prospective cohort study in a tertiary referral fetal medicine unit involving 628 consecutive fetuses undergoing chorionic villus sampling. The indication for chorionic villus sampling was an increased risk (more than 1:300) for trisomy 21 based on maternal age and nuchal translucency screening in 313 cases (54.7%), increased maternal age in 195 (34.1%), and other in 64 (11.2%). Immediately before chorionic villus sampling, an ultrasound examination was performed. The pattern of blood flow in the ductus venosus and the presence or absence of the nasal bones was noted.

RESULTS

A satisfactory examination of both ductus venosus and nasal bones was possible in 572 fetuses. Of these, 497 (86.9%) had a normal karyotype, and 47 (8.2%) were affected with Down syndrome. The likelihood ratio for trisomy 21 was 7.05 (95% confidence interval 4.27-11.64) in the case of abnormal ductus venosus flow and 6.42 (95% confidence interval 3.86-10.67) in the case of absent nasal bones.

CONCLUSION

In addition to increased fetal nuchal translucency, Down syndrome is significantly associated with first-trimester abnormal flow velocity patterns in the ductus venosus and hypoplasia of the nasal bones.

Ductus venosus blood flow assessment at 11 to 14 weeks of gestation and fetal outcome

OBJECTIVE

To evaluate the association between abnormal ductus venosus (DV) at 11-14 weeks' gestation and chromosomal abnormalities, structural defects and fetal outcome.

METHODS

DV flow-velocity waveform (DV-FVW) and nuchal translucency thickness (NT) were prospectively evaluated in 1217 singleton pregnancies.

RESULTS

The DV-FVW was abnormal in 84 fetuses, NT was above the 95th centile in 160 fetuses and both markers were observed in 41 fetuses. Chromosomal defects were diagnosed in 22 fetuses. The sensitivity, specificity and positive and negative predictive values for an abnormal karyotype were 86.4%, 86.9%, 11.9% and 99.7%, respectively, for an increased NT. These values were 68.2%, 96.9%, 31.3% and 99.3%, respectively, for DV-FVW abnormalities and 68.2%, 97.6%, 36.6% and 99.3%, respectively, when both markers were found simultaneously. Regarding structural defects, these values were 43.8%, 92.9%, 8.3% and 99.1% for an abnormal NT, 25.0%, 92.6%, 4.8% and 98.8% for DV-FVW abnormalities and 25.0%, 97.9%, 15.4% and 98.9% for both together. Considering those cases of unexplained fetal demise, the values were 44.4%, 85.9%, 5.0% and 98.9% for NT abnormalities, 22.2%, 92.6%, 4.8% and 98.6% for an abnormal DV-FVW and 22.2%, 98%, 15.4% and 98.7% for both. In cases with increased NT, the percentage of live births with normal karyotype and no major fetal structural defects decreased from 93.8% in normal DV-FVW fetuses to 77.3% in abnormal ones.

CONCLUSION

DV assessment at 11-14 weeks' gestation is useful in screening for fetal chromosomal abnormalities and may help to reduce the false-positive rate when combined with NT measurement. Abnormal DV-FVW is also associated with an increase in adverse perinatal outcome in fetuses with enlarged NT. However, the value of DV-FVW assessment in cases with normal NT is unclear.

Ductus venosus assessment at the time of nuchal translucency measurement in the detection of fetal aneuploidy

OBJECTIVE

To assess the potential value of ductus venosus Doppler studies in the detection of fetal aneuploidy on measurement of nuchal translucency.

METHODS

The pulsatility index for veins (PIV) and the lowest velocity during atrial contraction (A-wave) were determined in the fetal ductus venosus in 3382 consecutive pregnancies at 10 to 14 weeks and studied from December 1996 to December 2001. Nuchal translucency was also measured. The population studied included 1664 pregnancies at high risk and 1718 at low risk for fetal aneuploidy.

RESULTS

In relation to the prenatal detection of trisomy 21, the ductus venosus PIV was increased in 75% (36/48), the A-wave was decreased in 58% (28/48), and nuchal translucency was enlarged in 81% (39/48) of the trisomy 21 fetuses [71% (22/31) when nuchal translucency referrals were excluded]. The corresponding figures for trisomies 18 and 13 were 71, 58 and 83%, respectively, being 33, 33 and 33% for other unbalanced anomalies.

CONCLUSION

There is a high proportion of fetuses with trisomies 21, 18 and 13 (around 75%) in which the ductus venosus PIV is increased (above the 95th percentile) at 10 to 14 weeks, this proportion being similar to that observed for increased nuchal translucency measurement.

Jugular vein and carotid artery blood flow in fetuses with increased nuchal translucency at 10-14 weeks' gestation

OBJECTIVE

The aim of our study was to obtain measurements of the jugular vein and carotid artery pulsatility index (PI) at 10-14 weeks' gestation in chromosomally normal and abnormal fetuses with or without increased nuchal translucency (NT), in order to explore whether a relationship exists between increased NT and overperfusion of the head.

METHODS

This was a prospective study involving 179 pregnant women at high risk for chromosomal anomalies or structural malformations who were referred for chorionic villus sampling or first-trimester ultrasound examination at 10-14 weeks' gestation, respectively. Color and pulsed Doppler ultrasound were used to obtain jugular vein and carotid artery blood flow velocity waveforms at the level of the mid-neck. All Doppler measurements were obtained by a single investigator. The PIs of the jugular vein and carotid artery were correlated with NT measurement and fetal karyotype.

RESULTS

Doppler measurements of the jugular vein and carotid artery were successfully obtained in 90.5% of the fetuses. The fetal karyotype was abnormal in 13 cases, including three trisomies 21 and two trisomies 18, and normal in 149 cases. In the group with normal karyotype the NT was above the 95th percentile in 22 cases (15%). No correlation between the jugular vein or the carotid artery PI and the thickness of the NT was found. There were no significant differences when comparing the values of the jugular vein and carotid artery PI between the group with normal NT and the group with increased NT, or between the group with a normal karyotype and an abnormal karyotype.

CONCLUSION

Our results suggest that NT is not related to blood flow impedance in either the carotid artery or the jugular vein. Overperfusion and venous congestion of the head do not appear to be a causative pathophysiological mechanism involved in increased NT.

Effect of fetal gender on first-trimester ductus venosus blood flow

OBJECTIVES

Recent reports have suggested that nuchal translucency (NT) measurements in the first trimester may be influenced by fetal gender. Since both NT and central venous blood flow are considered to be related to fetal cardiac function, we investigated gender-related differences in first-trimester ductus venosus Doppler indices.

METHODS

A total of 73 male and 79 female normal fetuses at 10-14 weeks of gestation were included in the study. The pulsatility index for veins (PIV), peak velocity during ventricular systole (S-wave), time-averaged maximum velocity (TAMV) and A-wave velocity (A-wave) were recorded in each case and converted to the corresponding Z-scores.

RESULTS

The mean Z-score values of PIV, S-wave and TAMV were significantly lower in male fetuses compared to female fetuses (P < 0.01 for all three indices). By contrast, A-wave velocities were not different in the two groups. The correlation between S-wave velocity and TAMV was significant in both male (P < 0.001) and female (P < 0.001) fetuses, while PIV did not appear to be related to TAMV either in males (P = 0.90) or in females (P = 0.49). A-wave velocity had a significant negative correlation with PIV in both groups. Finally, PIV was significantly correlated with S-wave velocity in female fetuses (P < 0.01) but not in males (P = 0.14).

CONCLUSION

These findings suggest that early cardiovascular development may be different in male and female fetuses.

Prenatal diagnosis of hypoplastic left heart syndrome and trisomy 18 in a fetus with normal nuchal translucency and abnormal ductus venosus blood flow at 13 weeks of gestation

We describe a case of early prenatal diagnosis of a major congenital heart anomaly and trisomy 18 in a low-risk pregnant woman. Nuchal translucency (NT) measurement at 13 weeks' gestation was 1.2 mm and Doppler evaluation of the ductus venosus detected a persistent reversed flow during atrial contraction. This finding prompted us to perform fetal echocardiography which showed hypoplastic left heart syndrome. Karyotyping following chorionic villus sampling diagnosed trisomy 18. Review of the recent literature suggests that the finding of an abnormal ductus venosus Doppler pattern in the late first trimester of pregnancy may be an early sign of either congenital cardiac or chromosomal abnormality, even in the presence of normal NT screening.

Comprehensive assessment of fetal wellbeing: which Doppler tests should be performed?

PURPOSE OF REVIEW

Doppler applications in pregnancy are expanding exponentially. Flow velocity waveforms provide important information 12 weeks to term, from maternal vessels, placental circulation and fetal systemic vessels, with implications for both mother and fetus. As applications proliferate, awareness of the complexity of fetal and placental circulations, in normal pregnancy and in sequential responses to compromise, has also grown. The necessary data are now available to establish core values in Doppler evaluation for at-risk pregnancies.

RECENT FINDINGS

Uterine arteries depict maternal vascular effects of the invading placenta, predicting the frequency and severity of pre-eclampsia and intrauterine growth restriction. New evidence suggests early treatment based on this principle, significantly reduces these impacts. Umbilical artery Doppler reflects downstream placental vascular resistance, strongly correlated with intrauterine growth restriction and the multisystem effects of placental deficiency. Abnormalities are progressive, with reduction, loss, and finally a reversal of diastolic flow. When umbilical arteries become abnormal, the differentiation of fetal status requires Doppler information from systemic vessels. Middle cerebral artery changes begin when the redistribution of cardiac output reflects rising placental resistance, demonstrating 'brain sparing' when cerebrovascular dilation occurs. In the compromised intrauterine growth retarded fetus, precordial veins illustrate fetal cardiac function, changing as the respiratory status declines. This Doppler information is combined with biophysical profile scoring to determine the need for and timing of intervention.

SUMMARY

Doppler evaluation of at-risk pregnancies provides crucial prognostic and diagnostic detail about placentation and fetal adaptation. What has been research detail is now becoming the standard of care, in comprehensive fetal-maternal assessment.

Reference values for ductus venosus Doppler flow measurements at 10-14 weeks of gestation

OBJECTIVES

To calculate reference ranges for ductus venosus Doppler measurements obtained transabdominally at 10-14 weeks of gestation.

DESIGN

Two hundred and one normal fetuses with a crown-rump length (CRL) ranging from 38 to 88 mm were examined in a cross-sectional study. The pulsatility index for veins (PIV), peak velocity during ventricular systole (S-wave), lowest forward velocity during atrial contraction (A-wave) and time-averaged maximum velocity (TAMXV) were recorded from the ductus venosus. Flow velocity waveforms were also classified as normal or abnormal according to the presence (normal) or absence or reversal (abnormal) of frequencies during atrial contraction.

RESULTS

Three of 201 fetuses showed an abnormal flow pattern (1.5%; 95% exact confidence interval, 0.3-4.3%). In the 198 fetuses with a normal flow pattern, the mean PIV ranged from 1.07 at a CRL of 38 mm to 1.00 at a CRL of 88 mm (r = -0.093; P = 0.19). A significant increase in mean blood flow velocity with increasing CRL was noted for the S-wave (27.0 cm/s to 33.6 cm/s; r = 0.17; P = 0.02), the A-wave (5.9 cm/s to 7.8 cm/s; r = 0.14; P = 0.04) and the TAMXV (19.4 cm/s to 25.3 cm/s; r = 0.19; P < 0.01). Crown-rump length-specific reference ranges for each parameter were calculated using the method of scaled absolute residuals.

CONCLUSIONS

Abnormal ductus venosus flow patterns could be observed in normal fetuses, even if they ocurred with a low prevalence. Reference values for Doppler measurements were established in fetuses with normal patterns of flow.

DOPPLERVELOCIMETRIA DO DUTO VENOSO NO CÁLCULO DE RISCO PARA SÍNDROME DE DOWN NO PRIMEIRO TRIMESTRE DA GRAVIDEZ

OBJETIVO: Investigar a validade da Dopplervelocimetria do duto venoso em detectar a síndrome de Down entre 10 e 14 semanas de gestação e propor novo cálculo de risco. PACIENTES E MÉTODOS: Foram estudados 491 fetos, consecutivamente. Em 132 casos realizou-se estudo citogenético no material obtido por biópsia de vilosidade coriônica e em 359 o resultado baseou-se no fenótipo do recém-nascido. Em todos os fetos realizaram-se, além da ultra-sonografia de rotina, a medida da translucência nucal e a Dopplervelocimetria do duto venoso. Na análise estatística foram utilizados o teste paramétrico T de "student", a análise de variância e a regressão linear. Posteriormente, calcularam-se: sensibilidade, especificidade, valores preditivos positivo e negativo, probabilidade de falso-positivo e razões de probabilidades. RESULTADOS: Ocorreram 21 casos de trissomia do cromossomo 21. Desses casos, o fluxo no duto venoso durante a contração atrial foi ausente em três casos e reverso em 17 - sensibilidade de 95,2%. No grupo de fetos normais (470 casos), oito avaliações mostraram alterações do Doppler do duto venoso (especificidade de 98,2%, valores preditivos positivo e negativo de 71,4% e 99,8%, respectivamente, e razões de probabilidades positiva e negativa de 56 e 0,1, respectivamente). CONCLUSÕES: Nossos resultados preliminares sugerem que a presença de síndrome de Down pode ser fortemente suspeitada se houver fluxo reverso ou ausente no duto venoso. Especulamos a possibilidade de cálculo de novo risco para trissomia do 21 com base no Doppler do duto venoso. Utilizando o programa de risco da Fetal Medicine Foundation como risco basal, teríamos um fator multiplicador de aproximadamente 0,1 (razão de probabilidade negativa), caso duto normal, ou de 50 (razão de probabilidade positiva), caso duto reverso ou ausente, e assim, teremos novo risco corrigido.