First-trimester screening for Down syndrome with ductus venosus Doppler studies in addition to nuchal translucency and serum markers

Missed Down Syndrome Cases after First Trimester False-Negative Screening-Lessons to be Learned

Background and Objectives: Here, we performed a descriptive analysis of Down syndrome (DS) cases that were misdiagnosed and/or false-negative diagnosed after first trimester traditional screening via risk evaluation using ultrasound, biochemical markers, and different software programs. Our objective was to demonstrate the clear need to improve the application of prenatal DS screening programs using standardized ultrasound measurements, accurate pregnancy dating, analytical immunoassay performance, and properly selected medians. Materials and Methods: We performed a database search for the period 2010–2015 to analyze DS cases that were false-negative diagnosed after the first trimester of pregnancy, before the introduction of cell free fetal DNA-based tests by Romanian laboratories in 2015. First-trimester screening was performed using two software programs for prenatal DS risk calculation: Astraia and Prisca. The rationale for using both software programs was to assess the full risk using the maternal age combined test (based on nuchal translucency thickness, nasal bone, ductus venosus flow, tricuspid flow, free beta-human chorionic gonadotropin level, and serum pregnancy-associated plasma protein-A) and, in some cases, the triple test. Results: We identified seven DS cases that exhibited low risk for trisomy 21, and 6540 cases with a low risk for trisomy 21 and euploid fetus in the first trimester. Using Astraia software, 14 cases were diagnosed, and three cases were missed after risk calculation. Using Prisca software, four cases were missed. Additionally, one neonate had a missed prenatal diagnosis of atrio-ventricular canal defect. Conclusion: In Romania, the evaluation of DS risk depends on patient choice (without knowing the accuracy of the utilized tests) and on the operators’ skills. Both Astraia and Prisca software were developed by experts, who can prove their performance in DS screening. However, even in an ideal situation, false-negative results are possible. The application of first and second-trimester combined screening based on biochemical markers could be improved by the implementation of standardized protocols, professional guidelines for test application, and audit control.

Does first-trimester nuchal cord affect the blood flow in the ductus venosus? A prospective observational study

INTRODUCTION

Main objective of the present study was to investigate the association between the presence of nuchal cord (NC) and the measurement of the ductus venosus pulsatility index for veins (ductus venosus (DV) PIV).

METHODS

This was a prospective study of 1974 singleton pregnancies that underwent first-trimester screening at 11-13⁺⁶ gestational weeks. Color Doppler was used to demonstrate the presence of a NC in all cases and the DV PIV was calculated routinely, as part of the standard scan. The association between the presence of a NC and the DV PIV was then examined overall and at each gestational week.

RESULTS

A NC was demonstrated in 17.1% of cases. The incidence of nuchal cord was significantly higher at 13-13⁺⁶ weeks (24.7%, n = 119) compared to the one at 12-12⁺⁶ (16.5%, n = 192) and 11-11⁺⁶ weeks (7.9%, n = 26) (p < .001). No significant correlation was found between NC presence and DV PIV (p = .344). The DV PIV was 0.99 (± 0.15) for patients without NC versus 0.99 (± 0.15) for patients with NC (p = .34).

CONCLUSIONS

There was no association between the presence of a NC at 11-13⁺⁶ gestational weeks and the DV PIV.

First trimester ultrasound tests alone or in combination with first trimester serum tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three, rather than two copies of chromosome 21; or the specific area of chromosome 21 implicated in causing Down's syndrome. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life.Non-invasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive and false negative screening tests (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first trimester ultrasound markers alone, and in combination with first trimester serum tests for the detection of Down's syndrome.

SEARCH METHODS

We carried out extensive literature searches including MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), and The Database of Abstracts of Reviews of Effects (the Cochrane Library 2011, Issue 7). We checked reference lists and published review articles for additional potentially relevant studies.

SELECTION CRITERIA

Studies evaluating tests of first trimester ultrasound screening, alone or in combination with first trimester serum tests (up to 14 weeks' gestation) for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

We included 126 studies (152 publications) involving 1,604,040 fetuses (including 8454 Down's syndrome cases). Studies were generally good quality, although differential verification was common with invasive testing of only high-risk pregnancies. Sixty test combinations were evaluated formed from combinations of 11 different ultrasound markers (nuchal translucency (NT), nasal bone, ductus venosus Doppler, maxillary bone length, fetal heart rate, aberrant right subclavian artery, frontomaxillary facial angle, presence of mitral gap, tricuspid regurgitation, tricuspid blood flow and iliac angle 90 degrees); 12 serum tests (inhibin A, alpha-fetoprotein (AFP), free beta human chorionic gonadotrophin (ßhCG), total hCG, pregnancy-associated plasma protein A (PAPP-A), unconjugated oestriol (uE3), disintegrin and metalloprotease 12 (ADAM 12), placental growth factor (PlGF), placental growth hormone (PGH), invasive trophoblast antigen (ITA) (synonymous with hyperglycosylated hCG), growth hormone binding protein (GHBP) and placental protein 13 (PP13)); and maternal age. The most frequently evaluated serum markers in combination with ultrasound markers were PAPP-A and free ßhCG.Comparisons of the 10 most frequently evaluated test strategies showed that a combined NT, PAPP-A, free ßhCG and maternal age test strategy significantly outperformed ultrasound markers alone (with or without maternal age) except nasal bone, detecting about nine out of every 10 Down's syndrome pregnancies at a 5% false positive rate (FPR). In both direct and indirect comparisons, the combined NT, PAPP-A, free ßhCG and maternal age test strategy showed superior diagnostic accuracy to an NT and maternal age test strategy (P < 0.0001). Based on the indirect comparison of all available studies for the two tests, the sensitivity (95% confidence interval) estimated at a 5% FPR for the combined NT, PAPP-A, free ßhCG and maternal age test strategy (69 studies; 1,173,853 fetuses including 6010 with Down's syndrome) was 87% (86 to 89) and for the NT and maternal age test strategy (50 studies; 530,874 fetuses including 2701 Down's syndrome pregnancies) was 71% (66 to 75). Combinations of NT with other ultrasound markers, PAPP-A and free ßhCG were evaluated in one or two studies and showed sensitivities of more than 90% and specificities of more than 95%.High-risk populations (defined before screening was done, mainly due to advanced maternal age of 35 years or more, or previous pregnancies affected with Down's syndrome) showed lower detection rates compared to routine screening populations at a 5% FPR. Women who miscarried in the over 35 group were more likely to have been offered an invasive test to verify a negative screening results, whereas those under 35 were usually not offered invasive testing for a negative screening result. Pregnancy loss in women under 35 therefore leads to under-ascertainment of screening results, potentially missing a proportion of affected pregnancies and affecting test sensitivity. Conversely, for the NT, PAPP-A, free ßhCG and maternal age test strategy, detection rates and false positive rates increased with maternal age in the five studies that provided data separately for the subset of women aged 35 years or more.

AUTHORS' CONCLUSIONS

Test strategies that combine ultrasound markers with serum markers, especially PAPP-A and free ßhCG, and maternal age were significantly better than those involving only ultrasound markers (with or without maternal age) except nasal bone. They detect about nine out of 10 Down's affected pregnancies for a fixed 5% FPR. Although the absence of nasal bone appeared to have a high diagnostic accuracy, only five out of 10 affected Down's pregnancies were detected at a 1% FPR.

Observational study comparing the performance of first-trimester screening protocols for detecting trisomy 21 in a North Indian population

OBJECTIVE

To evaluate first-trimester screening protocols for detecting trisomy 21 in an Indian population.

METHODS

The present prospective study collected data from women with singleton pregnancies and a crown-to-rump length of 45-84 mm who presented at the fetal medicine unit of a tertiary care center in North India between June 1, 2006, and December 31, 2015, for combined first-trimester screening. Maternal age, nuchal translucency, nasal bone, and maternal serum levels of free beta human chorionic gonadotropin and pregnancy-associated plasma protein A were assessed for calculating the risk of trisomy 21. Tricuspid regurgitation and qualitative analysis of ductus venosus data were available from June 2010, and were included where available. Trisomy-21 detection rates were calculated for various screening protocols and were compared.

RESULTS

There were 4523 women screened and 24 records of trisomy 21. Combined screening with maternal age, nuchal translucency, nasal bone, tricuspid regurgitation, and ductus venosus demonstrated optimal detection and false-positive rates of 93.8% and 1.9%, respectively. Screening using only maternal age yielded a detection rate of 37.5%; using fixed nuchal translucency cut-off values of 2.5 and 3 mm resulted in detection rates of 66.7% and 37.5%, respectively.

CONCLUSION

Combined first-trimester screening performed well in an Indian population; combining maternal age, nuchal translucency, nasal bone, ductus venosus, and tricuspid regurgitation yielded the most accurate screening.

Is there a role for fetal ductus venosus and hepatic artery Doppler in screening for fetal aneuploidy in the first trimester?

OBJECTIVE

The aim of the present study was to evaluate the utility of ductus venosus (DV) and hepatic artery (HA) doppler in pregnant women who have high risk for aneuploidy in first trimester combined screening.

METHODS

This prospective study was performed between February 2011 and February-2012, at a tertiary referral hospital. Singleton pregnancies with high risk for aneuploidy in combined screening test and normal nuchal translucency (NT) measurements were included in the study group. Measurements of DV Pulsatility Index of Veins (PIV) and HA Pulsatility Index (PI) were compared between the study group and controls.

RESULTS

Within the study period, 104 women with singleton pregnancies were evaluated for DV and HA measurements and among these, 64 women met the inclusion criteria. A control group that comprised 40 women with similar gestational age, normal NT measurements and low-risk in first trimester combined tests was generated. DV-PIV measurements were significantly higher (p = 0.03), whereas HA-PI measurements were similar (p > 0.05) in women who had high-risk for aneuploidy in first trimester combined test.

CONCLUSION

We concluded that the addition of DV-PIV and HA-PI measurements to the first trimester combined screening might increase the accuracy for Down syndrome detection.

Efficacy of the genetic sonogram in a stepwise sequential protocol for down syndrome screening

OBJECTIVES

The purpose of this study was to evaluate the efficacy of the genetic sonogram in Down syndrome screening for women who have received the stepwise sequential test.

METHODS

This retrospective cohort study included women with singleton pregnancies who underwent stepwise sequential (first-trimester combined and second-trimester serum) screening and then had a genetic sonogram between March 2005 and January 2010. Stepwise sequential Down syndrome risks were multiplied by either a positive or negative likelihood ratio based on the second-trimester sonographic findings to determine the final Down syndrome risk. A final Down syndrome risk of 1:270 or higher was considered screen positive.

RESULTS

A total of 6286 women fulfilled our criteria, including 17 with Down syndrome-affected fetuses. After stepwise sequential testing, the Down syndrome detection rate was 88.2% (15 of 17), and after the genetic sonogram, there was a non-significant reduction in detection to 82.4% (14 of 17; P > .05). For the 6269 unaffected pregnancies, the genetic sonogram converted 58 screen-negative results (1%) to positive and 183 screen-positive results (3.1%) to negative. The net effect was a change in the false-positive rate from 6.2% (390 of 6269) after stepwise sequential screening to 4.2% (266 of 6269) after the genetic sonogram.

CONCLUSIONS

The genetic sonogram should be applied cautiously for women who have received prior prenatal screening tests. Women with screen-positive results need to be counseled that a negative sonographic result can be falsely reassuring. Conversely, for women with screen-negative results who have a risk close to the cutoff, a sonographic examination could assist in the decision of whether to accept or reject amniocentesis.

Likelihood ratios to apply for nasal bone, ductus venosus and tricuspid flow at the 11-13 weeks' scan in down syndrome screening

OBJECTIVE

To assess the feasibility of nasal bone (NB), ductus venosus (DV) and tricuspid flow (TF) at the 11-13 weeks' scan, calculate likelihood ratios for each of the markers and evaluate their efficacy in expanded and contingent screening strategies for Down syndrome.

MATERIAL AND METHODS

NB, DV and TF were assessed in 11,261 singleton fetuses undergoing first trimester combined screening. For each marker, Down syndrome detection rate (DR), false positive rate (FPR), positive, negative and isolated likelihood ratios (PLR, NLR and iLR) were calculated. Likelihood ratios were multiplied to the combined test risk either to the entire population or to the intermediate risk group (expanded and sequential strategies, respectively).

RESULTS

Down syndrome was diagnosed in 101 pregnancies. Feasibility for marker assessment ranged from 71 to 97%, DRs for isolated markers from 20 to 54% and FPRs from 1.3 to 5.3%. PLR ranged from 10 to 15, NLR from 0.5 to 0.8 and iLR from 3.9 to 5.6. When ultrasound markers were added to both strategies, a significant FPR reduction was observed.

CONCLUSION

The application of NB, DV and TF likelihood ratios to the combined test risk, either in an expanded or contingent strategy, result in a FPR reduction.

Analysis of three different strategies in prenatal screening for Down's syndrome in twin pregnancies

OBJECTIVES

To compare the performance of three different strategies in prenatal screening for Down's syndrome in twins [nuchal translucency, the combined test, the combined test + ductus venosus pulsatility index (DVPI)].

METHODS

We included 277 twin pregnancies with two cases of trisomy 21 (both dichorionic). We performed a computer simulation of Down's syndrome NT screening, combined test screening and the combined test with the addition of DVPI screening using the commercialized software SsdwLab6. The strategies were compared using the area under the receiver operating characteristic curve.

RESULTS

NT screening false-positive rate (FPR) was 10.9% (95% CI: 8.3-13.5). The combined test FPR was 6.2% (95% CI: 4.1-8.2%) and the combined test plus DVPI was 6% (95% CI: 4-8). FPR was higher in advanced maternal age patients. Detection rate was 100% in all cases. The area under the curve was 0.987 (95% CI: 0.972-0.994) in NT screening; 0.987 (95% CI: 0.978-0.997) in the combined test and 0.983 (95% CI: 0.977-0.996) in the combined test + DVPI.

CONCLUSIONS

Down's syndrome screening is feasible in twins with low FPR. The results of this study are similar to the results achieved in singletons. The combined test appears to be the most effective. The addition of DVIP does not significantly improve the prenatal screening for trisomy 21.

Cumulative sum plots and retrospective parameters in first-trimester ductus venosus quality assurance

OBJECTIVE

This study aimed to evaluate the application of two quality assurance methods to the ductus venosus pulsatility index (DVPI), as a first-trimester aneuploidy marker, including retrospective assessment of distribution parameters and cumulative sum (CUSUM) plots.

METHODS

The DVPI was measured in 14 444 singleton fetuses at 11+0 to 13+6 weeks in two Fetal Medicine centers during a 4-year period. Sonologist-specific quality assurance distribution parameters, previously described for nuchal translucency, were assessed: the median multiples of the median (MoM), the logarithmic standard deviation of DVPI MoMs and the weekly DVPI percent decrease. Quality assurance results were compared between median MoMs and MoM-based CUSUM plots.

RESULTS

When sonologist-specific DVPI distribution parameters were retrospectively applied for quality assurance, a 1.0 median MoM, a 0.1 median logarithmic standard deviation and a 3.4 median weekly DVPI drop percentage were observed. CUSUM plots showed good agreement with 0.9-1.1 MoMs range for median MoM, in the assessment of sonologist-specific performances.

CONCLUSION

Retrospective and prospective DVPI quality assurance methods appear to be applicable to DVPI at 11+0 to 13+6 weeks. Its use should be encouraged if DVPI is to be added to first-trimester Down syndrome or cardiac defects screening.

Screening performance for trisomy 21 comparing first trimester combined screening and a first trimester contingent screening protocol including ductus venosus and tricuspid flow

OBJECTIVE

To compare the standard first trimester combined risk assessment for trisomy 21 with a contingent screening protocol including tricuspid flow and ductus venosus flow.

MATERIAL AND METHOD

Women with singleton pregnancies and a first trimester combined risk assessment>1:1000 were included. They all had additional assessment of the ductus venosus and the tricuspid flow. We compared screening performance in two screening strategies: (a) First trimester combined screening strategy based on the individual risk results from the routine screening test and (b) Contingent screening strategy based on a combination of the routine test results and additional ultrasound markers.

RESULTS

We included 917 women in the study, 894 in the euploid group and 23 in the trisomy 21 group. Using a contingent screening strategy resulted in a significant decrease in screen positive rate from 48.3% to 17.7% (p<0.001) in the studied population. There was no statistical difference in detection rate between the two screening strategies.

CONCLUSION

There is increasing evidence in favour of using additional ultrasound markers as part of contingent screening protocols in the first trimester. We do suggest performing further studies in routine clinical settings to provide validation of the available risk algorithms.

Is the addition of the ductus venosus useful when screening for aneuploidy and congenital heart disease in fetuses with normal nuchal translucency?

OBJECTIVE

The aim of this study was to examine the possible role of Doppler ultrasound assessment of ductus venosus (DV) blood flow at 11⁺⁰-13⁺⁶ weeks' gestation in fetuses with normal nuchal translucency (NT) in screening for autosomal trisomies (AT) and for congenital heart diseases (CHD) in chromosomally normal fetuses.

METHODS

First-trimester combined screening for trisomy 21 (T21) was carried out prospectively for 7 years in singleton pregnancies. NT and the pulsatility index for DV (DVPI) were calculated. The DV was analyzed according to its association with AT and CHD. The detection rate (DR), false-positive rate (FPR), positive predictive value (PPV), and odds ratio (OR) for abnormal DV were calculated.

RESULTS

Abnormal DV as an early marker of euploid CHD gives a DR of 12.5%, an FPR of 4.3%, a PPV of 1.4%, and a negative predictive value (NPV) of 99.5%, with an OR of 3.1 (95% CI 1.3-7.4). Moreover, abnormal DV as an early marker of AT shows a DR of 35.7%, an FPR of 4.3%, a PPV of 1.2%, an NPV of 99.9%, and an OR of 12.3 (95% CI 4.1-36), and the values are 33.3, 4.3, 0.97, and 99.9% and 11 (95% CI 3.2-36.9), respectively, for T21.

CONCLUSIONS

Our data supports the association between increased DVPI and CHD or AT. The sensitivity of this marker is not strong enough to be used a screening test.

First trimester contingent test as a screening method for Down's syndrome. A prospective study in the general population

OBJECTIVES

To evaluate the possibility of implementing a contingent test as a screening method for Down's syndrome (DS) in the first trimester of pregnancy, and assess its sensitivity (Sen) and false positive rate (FPR).

METHODS

Prospective study covering a 4-year study period (July 2006-June 2010). Pregnant women were offered a combined test (CT) as the first step of a contingent test. An intermediate risk group is identified in the CT (1/101 and 1/1000) and offered an ultrasound assessment of secondary s (nasal bone, ductus venosus, tricuspid regurgitation).

RESULTS

CTs were performed on 10,452 pregnant women (24 cases of DS). In the intermediate risk group, which had 7 cases of DS, we performed secondary ultrasound marker assessment on 98.1% (1,017/1,036). The CT and the contingent test had a Sen of 83% (95% CI; 67.9-98) (20/24) and 70.8% (95% CI; 52.6-88.9) (17/24) with an FPR of 3% (95% CI; 2.7-3.3) (316/10,430) and 2% (95% CI; 1.7-2.3) (220/10,408), respectively.

CONCLUSIONS

With the contingent test, we managed to reduce the FPR, but the Sen was too low for use as a screening method for DS.

First-trimester screening for chromosomal abnormalities by integrated application of nuchal translucency, nasal bone, tricuspid regurgitation and ductus venosus flow combined with maternal serum free β-hCG and PAPP-A: a 5-year prospective study

OBJECTIVE

To investigate the performance of first-trimester screening for chromosomal abnormalities by integrated application of nuchal translucency thickness (NT), nasal bone (NB), tricuspid regurgitation (TR) and ductus venosus (DV) flow combined with maternal serum free β-human chorionic gonadotropin (fβ-hCG) and pregnancy-associated plasma protein-A (PAPP-A) at a one-stop clinic for assessment of risk (OSCAR).

METHODS

In total, 13,706 fetuses in 13,437 pregnancies were screened for chromosomal abnormalities during a period of 5 years. Maternal serum biochemical markers and maternal age were evaluated in combination with NT, NT + NB, NT + NB + TR, and NT + NB + TR + DV flow data in 8581, 242, 236 and 4647 fetuses, respectively.

RESULTS

In total, 51 chromosomal abnormalities were identified in the study population, including 33 cases of trisomy 21, eight of trisomy 18, six of sex chromosome abnormality, one of triploidy and three of other unbalanced abnormalities. The detection rate and false-positive rate (FPR) for trisomy 21 were 93.8% and 4.84%, respectively, using biochemical markers and NT, and 100% and 3.4%, respectively, using biochemical markers, NT, NB, TR and DV flow.

CONCLUSION

While risk assessment using combined biochemical markers and NT measurement has an acceptable screening performance, it can be improved by the integrated evaluation of secondary ultrasound markers of NB, TR and DV flow. This enhanced approach would decrease the FPR from 4.8 % to 3.4 %, leading to a lower number of unnecessary invasive diagnostic tests and subsequent complications, while maintaining the maximum level of detection rate. Pre- and post-test genetic counseling is of paramount importance in either approach.

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.

The assessment of nuchal translucency and serum markers for down syndrome screening with ductus venosus Doppler measurements in the first trimester

OBJECTIVE

The aim of the study was to improve nuchal translucency (NT) and serum marker Down syndrome (Tri21) screening methods by including fetal ductus venosus (DV) Doppler measurements.

MATERIAL AND METHODS

A total of 213 pregnant women were screened consecutively by combining maternal age, fetal NT and maternal serum pregnancy associated plasma protein A (PAPP-A) and free β-human chorionic gonadotropin (f β-HCG) values at 11-14 weeks of gestation. Also, a DV Doppler analysis was performed for the contribution to the screening for Tri21 and other fetal anomalies or adverse pregnancy outcomes.

RESULTS

Twelve fetuses had DV PI measurements above the 95th percentile and two (17%) developed intrauterine growth retardation. DV PI values negatively correlated with birth weight (p=0.013, r=0.171). Two patients had T 21 among the study group (0.9%) with abnormal biochemical screening results. In these with Tri21, the combined test risk was above the suggested limit (>1/250). PAPP-A was <0.4 MoM in 23, and f β-HCG was >1.91 MoM in 49 patients. The rates of false positivity were 10% for PAPP-A and 22% for f β-HCG. The sensitivity, specificity, positive and negative predictive values of the combined test was 100%, 95%, 20% and 100%, respectively.

CONCLUSION

The combined test has high sensitivity and specificity for Tri21 detection. The addition of DV Doppler ultrasound in the first trimester might have the advantage of predicting some adverse pregnancy outcomes. However, in the Turkish population, further studies with larger numbers of patients will be needed to establish the usefulness of DV for the detection of Tri21 or the prediction of some major cardiac anomalies.

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.

Complete trisomy 21 vs translocation Down syndrome: a comparison of modes of ascertainment

OBJECTIVE

To compare the indications for invasive prenatal testing resulting in the detection of translocation Down syndrome and complete trisomy 21.

STUDY DESIGN

This case control study was based on a large amniocentesis and chorionic villi samples database (n = 534,795). All specimens with translocation Down syndrome (n = 203) comprised the translocation group and were compared with a maternal age-matched group (4 to 1, n = 812) in which complete trisomy 21 was detected. Women with a normal karyotype were randomly selected (n = 812) and served as controls. Indications for invasive testing were compared among the 3 paired groups using χ(2) analysis.

RESULTS

There were no differences in the incidence of abnormal first- and second-trimester screening tests between the translocation Down syndrome and the complete trisomy 21 groups. History of prior aneuploidy was significantly more frequent in the translocation Down syndrome group, as compared with either complete trisomy 21 fetuses or normal controls.

CONCLUSION

Fetuses with translocation Down syndrome present with the same screening abnormalities as fetuses with complete trisomy 21.

Abnormal first-trimester ductus venosus blood flow: a marker of cardiac defects in fetuses with normal karyotype and nuchal translucency

OBJECTIVE

To evaluate the independent contribution of ductus venosus (DV) blood flow assessment at 11-14 weeks' gestation to the prediction of congenital heart defects (CHD) in chromosomally normal fetuses, irrespective of the value of the nuchal translucency thickness (NT).

METHODS

During a 4-year period, all singleton pregnancies from 11 + 0 to 13 + 6 weeks' gestation were scanned for NT and DV blood flow in a tertiary center. Abnormal DV blood flow was defined as either absent or reversed flow during atrial contraction (AR-DV). Fetal echocardiography was performed in all cases with either NT > 99(th) percentile or AR-DV. Follow-up was assessed by postnatal examination or autopsy in cases of termination of pregnancy or perinatal death.

RESULTS

A total of 6120 pregnancies were scanned at a median gestational age of 12 weeks, and 45 cases of CHD were detected. AR-DV was found in 206 fetuses, of which 145 (70.4%) had a normal karyotype. Among fetuses with AR-DV and normal karyotype, 11 cases of CHD were diagnosed, giving a sensitivity of 24.4%, a positive predictive value of 7.6% and an odds ratio of 9.8. Increased NT (> 99(th) centile) was present in 55 of the 145 (37.9%) cases with AR-DV and normal karyotype, and in 6/11 (54.5%) of those with CHD. Thus, the group of 90 fetuses with abnormal DV blood flow and normal NT contained five cases of CHD, for a sensitivity of 11.1%, a positive predictive value of 5.5% and an odds ratio of 8.5. Right-heart anomalies were predominant in those cases with isolated AR-DV (4/5), but no specific CHD pattern was found in those with increased NT. The detection rate of CHD by the combined use of increased NT and/or AR-DV in the first trimester improved from 28.9% (13/45) to 40.0% (18/45).

CONCLUSIONS

In experienced hands, abnormal DV blood flow in the first trimester is an independent predictor of CHD and should constitute an indication for early echocardiography. In this study, the use of DV blood flow assessment increased early detection of CHD by 11% with respect to the use of NT measurement alone.

Influence of nuchal cord on ductus venosus assessment at 11 to 13 + 6 weeks' gestation

OBJECTIVES

To assess the influence of the presence of nuchal cord (NC) on the evaluation of the fetal ductus venosus flow velocity waveform (DV-FVW).

METHODS

This prospective study included 1174 normal non-selected singleton pregnancies between 11 and 13 + 6 weeks' gestation. We recorded the presence or absence of NC around the fetal neck, and assessed its relationship with the qualitative assessment and quantitative measurement of the DV-FVW.

RESULTS

We observed NC around the fetal neck in 6.73% of cases and detected reversed flow of the a-wave of the DV-FVW in 2.98% of cases. In the group without NC, 21 of 1095 had reversed flow in the DV-FVW (1.9%; 95% CI, 1.28-3.02), whereas in the group with NC, 14 of 79 had reversed flow in the DV-FVW (17.7%; 95% CI, 16.67-40.35). We found a lower pulsatility index in fetuses without NC in comparison to those with NC (P < 0.001). We also found an association between the presence of NC and an increased occurrence of absent and reversed a-wave of the flow velocity waveforms (P < 0.001). On multivariate logistic regression analysis, a much higher occurrence of reversed DV-FVW a-wave was detected in fetuses with NC and smaller crown-rump length, and a much higher occurrence of absent DV-FVW a-wave was found in fetuses with NC and a higher maternal body mass index.

CONCLUSIONS

The presence of NC modifies the sonographic findings in the qualitative and quantitative evaluation of the DV-FVW.

Ductus venosus pulsatility index as an antenatal screening marker for Down's syndrome: use with the Combined and Integrated tests

OBJECTIVES

To assess the value of ductus venosus blood flow (expressed as pulsatility index, DVPI) in antenatal Down's syndrome screening when used with the Combined and Integrated tests.

METHODS

DVPI measurements between 10 and 13 weeks' gestation in 66 Down's syndrome and 7184 unaffected pregnancies were collected from women attending the Hospital Clinic, Barcelona, for antenatal care from 1999 to 2007 and combined with the Serum Urine and Ultrasound Screening Study (SURUSS) data to model screening performance, safety and cost-effectiveness of the screening tests with and without DVPI.

RESULTS

The median DVPI multiple of the normal median in Down's syndrome pregnancies was 1.55 (95% CI 1.36-1.73). As a single screening marker without using maternal age, DVPI has a 62% detection rate for a 5% false-positive rate. At a 90% detection rate (first trimester measurements at 11 weeks' gestation) the addition of DVPI reduced the false-positive rate of the Combined test from 8.5% to 4.6% and the Integrated test from 2.0% to 1.1%, with a corresponding reduction in fetal losses from diagnostic procedures. There was no material loss of cost-effectiveness.

CONCLUSION

Addition of DVPI measurements to the Combined and Integrated tests substantially improves the efficacy and safety of antenatal Down's syndrome screening.

Prenatal testing for Down syndrome: comparison of screening practices in the UK and USA

Prenatal testing for Down Syndrome is a topic covered in every genetic counselor's training as it constitutes the main workload of genetic counselors in prenatal settings. Most Western countries nowadays offer some type of testing for Down Syndrome. However, practices vary according to country with regards to what tests are offered, insurance coverage and the legal situation concerning the option of terminating an affected pregnancy. In view of the growing interest in international genetic counseling issues, this article aims to compare prenatal testing practices in two English-speaking countries: the United Kingdom and the United States of America. A case will be presented to highlight some of the differences in practice. The topic underlines important implications for genetic counseling practice, such as patients' understanding of testing practices, risk perception, counseling provision and impact of prenatal testing results.

Role of uterine artery Doppler in interpreting low PAPP-A values in first-trimester screening for Down syndrome in pregnancies at high risk of impaired placentation

OBJECTIVES

Low maternal serum levels of pregnancy-associated plasma protein-A (PAPP-A) are associated with both increased risk of aneuploidies and impaired trophoblastic invasion, while high uterine artery (UtA) resistance is associated with impaired trophoblastic invasion but not with an increased risk of aneuploidies. The aim of this study was to determine whether high UtA resistance plays a role in explaining low PAPP-A levels in the absence of aneuploidies.

METHODS

This was a prospective study of 116 singleton pregnancies at high risk for impaired placentation (having at least one major risk factor: prior history of pre-eclampsia, pregestational diabetes mellitus, chronic hypertension, chronic kidney disease, body mass index >30, autoimmune disorder, thrombophilia or recurrent pregnancy loss), booked for routine assessment of risk for aneuploidies by means of the first-trimester combined screening test (nuchal translucency thickness (NT) + PAPP-A + beta-human chorionic gonadotropin (beta-hCG)). Measurement of NT and the mean UtA pulsatility index (PI) were carried out at the 11 to 13 + 6-week scan. All values were calculated in multiples of the median (MoM) adjusted for gestational age. A cut-off risk of 1/270 at time of sampling was adopted to differentiate high- from low-risk groups for trisomy 21.

RESULTS

There were 108 patients deemed to be at low risk for trisomy 21 and eight at high risk. None had chromosomal defects, giving a false-positive rate for trisomy 21 of 6.9%. The greatest differences between patients at low risk and those at high risk for trisomy 21 were found in their PAPP-A (0.98 vs. 0.38 MoM, P < 0.01) and beta-hCG (1.09 vs. 1.77 MoM, P = 0.04) values. Greater NT thickness (1.02 vs. 0.90 MoM) and higher mean UtA-PI (1.05 vs. 0.96 MoM) were recorded in the high-risk group, although the differences did not reach statistical significance (P = 0.19 and 0.40, respectively). After log-transformation there were no significant correlations between mean UtA-PI and NT and between mean UtA-PI and beta-hCG. There was a significant negative linear correlation between mean UtA-PI and PAPP-A (r = -0.331; P < 0.01). After adjusting the PAPP-A values by UtA-PI, the false-positive rate for trisomy 21 decreased to 2.6%.

CONCLUSION

Mean UtA-PI at the 11 to 13 + 6-week scan may be an effect-modifier variable for PAPP-A that should be taken into account in the first-trimester combined screening for aneuploidies, at least in pregnancies at high risk for impaired placentation.

Comparison of modes of ascertainment for mosaic vs complete trisomy 21

OBJECTIVE

We sought to compare the indications for amniocentesis leading to the detection of either mosaicism of trisomy 21 (mosaic-T21) or complete trisomy 21 (T21).

STUDY DESIGN

A retrospective review of a large amniocentesis database (n = 494,163) was conducted. All specimens with mosaic-T21 (n = 124) were compared with a maternal age-matched group of T21 fetuses (n = 496). Samples with normal karyotypes were matched for maternal age and served as normal controls (n = 496). The chi(2) testing was used for statistical analysis.

RESULTS

The presence of an abnormal first-trimester screen, abnormal sonographic findings, and specifically the single sonographic abnormalities of either a cystic hygroma or a cardiac anomaly were significantly less common in the mosaic-T21 as compared with the T21 group. There were no such differences between the mosaic-T21 and the normal control group.

CONCLUSION

Fetuses with mosaic-T21, similar to those with normal karyotype, do not present with the same abnormal screening tests as fetuses with T21.

Learning curve for Doppler assessment of ductus venosus flow at 11 + 0 to 13 + 6 weeks' gestation

OBJECTIVE

To determine the number of scans necessary for training sonographers to examine accurately the ductus venosus at 11 + 0 to 13 + 6 weeks' gestation.

METHODS

Ten sonographers with prior extensive experience in the measurement of nuchal translucency thickness were given practical training in the accurate assessment of the ductus venosus. They were then asked to examine the ductus venosus during the routine 11 + 0 to 13 + 6 weeks' scan. Each scan was assessed by an experienced sonographer and classified as being successful or unsuccessful (failure to obtain a waveform, poor quality image with contamination or wrong classification of the A-wave). Each sonographer performed a total of 300 examinations, the data were analyzed in 15 groups of 20 examinations and in each group the percentage of unsuccessful examinations was calculated.

RESULTS

In the total 3000 cases examined by the 10 sonographers there were 2849 (95.0%) successful examinations and 151 unsuccessful, including 104 failures to obtain a waveform, 30 cases where the quality of the image was considered to be inadequate and 17 cases in which the classification of the A-wave was wrong. The overall frequency of unsuccessful examinations decreased significantly with the number of scans carried out (r = 0.982, P < 0.0001). The sonographers required an average of 80 examinations before they could successfully examine the ductus in at least 19 of a group of 20 scans. Although one of the 10 trainees achieved this standard within the first block of 20 scans some of the sonographers required training in 100 cases.

CONCLUSION

Competence in Doppler assessment of the ductus venosus is achieved only after extensive supervised training.

Nuchal Translucency and First Trimester Risk Assessment

First-trimester risk assessment for fetal aneuploidy using nuchal translucency (NT) measurement is rapidly gaining popularity in the United States. In combination with maternal serum markers in the first trimester, the screening performance is exceptionally good, with detection rates of more than 80% at a screen positive rate of 5%. Recently, the method has been validated for screening for Down syndrome and other aneuploidies in multicenter trials in the United States and elsewhere. Compliance with established criteria for measurement of the NT is essential to achieve uniform reliability and high screening test sensitivity. There is an international consensus about the importance of specific training in the NT examination, conformity to standards of NT measurement, and regular audit for quality assurance. In the United States, the Nuchal Translucency Quality Review program has been developed to administer credentialing and quality review for registered practitioners. The Nuchal Translucency Quality Review credentials signify the proficiency of the sonographer or sonologist in NT measurement and participation in a regular quality assurance audit. We encourage accreditation of clinical sites offering first-trimester risk assessment to ensure the highest quality care.

Aneuploidy screening in the first trimester

This article reviews the performance of first trimester screening for chromosomal anomalies using various combinations of ultrasound and maternal serum biochemical modalities. Detection rates in excess of 90% can be routinely achieved for Trisomy 21, Trisomy 13, Trisomy 18 using a combination of fetal nuchal translucency (NT) thickness and maternal serum free ss-hCG and PAPP-A at 11 + 0 to 13 + 6 weeks of gestation.

[Abdominal vascular malformations and Down syndrome]

Malformations of the abdominal venous system are rare vascular disorders. These entities are associated with other malformations and with chromosomal anomalies such as trisomy 21. Abdominal venous malformations are probably the most frequent congenital vascular malformations in Down syndrome. Prenatal diagnosis allows the early follow-up and treatment of complications. We present a case of Down syndrome associated with an abdominal venous malformation diagnosed at the first trimester of pregnancy.

First-trimester screening

Screening for fetal chromosome abnormalities, particularly for trisomy 21, has made dramatic advances. Better screening demonstrates that "high-risk" patients--particularly over age 35--can have lower risk of defects than younger unscreened women. This has caused reduction of amniocentesis for older patients and made screening available for younger patients who have the universal 2% to 3% risk. This means lower procedural-related losses of normal fetuses, and better resource allocation. The trend toward first-trimester detection of structural defects continues; a normal survey is reassuring and helps exclude major defects. Based on screening results, patients can be triaged into early follow-up and possible amniocentesis as 14 to 16 weeks, or a later detailed anatomic survey at 18 to 20 weeks.

An increased thermal index can be achieved when performing Doppler studies in obstetric sonography

OBJECTIVE

The present study was aimed at evaluating acoustic outputs during clinical ultrasound examinations, as expressed by the thermal index (TI) and the mechanical index (MI), during the second half of pregnancy and comparing acoustic outputs between B-mode and Doppler examinations.

METHODS

Patients with suspected fetal growth problems undergoing Doppler studies of the fetal circulation in addition to B-mode sonography were selected. Examinations took place between 21 and 40 weeks' gestation. An obstetrician collected data prospectively. Sonographers were unaware of the data being sought. The analysis of variance test was applied for differences in continuous variables.

RESULTS

A total of 63 examinations were evaluated. The mean gestational age +/- SD was 31.6 +/- 5.1 weeks. The mean duration of the total examinations was 17.6 +/- 8.6 minutes, whereas the Doppler studies lasted 0.9 +/- 0.8 minutes. The TI was significantly higher in the pulsed wave Doppler studies (mean, 1.5 +/- 0.5; range, 0.9-2.8) and color flow imaging studies (mean, 0.8 +/- 0.1; range, 0.6-1.2) compared with B-mode sonography (mean, 0.3 +/- 0.1; range, 0.1-0.7; P < .01). During the examination, 190 B-mode MI variations were recorded (mean, 1.1 +/- 0.1), which were comparable with those of the 31 color flow Doppler studies (mean, 1.0 +/- 0.1; P = .09) but higher than the 190 pulsed wave Doppler MI variations (mean 0.9 +/- 0.2; P < .001).

CONCLUSIONS

Increased acoustic output levels, as expressed by TI levels, are reached during obstetric Doppler studies. In particular, TI levels may reach 1.5 and higher. Doppler procedures should be performed with caution and be as brief as possible during obstetric sonography.

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.

An update on antenatal screening for Down's syndrome and specific implications for assisted reproduction pregnancies

Since the introduction of antenatal serum screening for Down's syndrome (DS) more than two decades ago, several screening approaches have been utilized in routine clinical practice. The current DS screening strategies involve mid-trimester serum biochemistry tests, first trimester tests combining sonographic markers and serum biochemistry and integration of first and second trimester markers. In this review, we evaluate the performance of DS screening strategies according to the Serum, Urine and Ultrasound Screening Study (SURUSS), the First and Second Trimester Evaluation of Risks (FASTER) Trial and the Serum Biochemistry and Fetal Nuchal Translucency Screening (BUN) Study. We also evaluate the performance of first trimester screening in studies and meta-analyses by other groups. Specific issues related to assisted reproduction technology (ART) pregnancies are also addressed in this review.