Screening for fetal aneuploidies and fetal cardiac abnormalities by nuchal translucency thickness measurement at 10-14 weeks of gestation as part of routine antenatal care in an unselected population

Cardiac Axis in Early Gestation and Congenital Heart Disease

Congenital heart defects represent the most common structural anomalies observed in the fetal population, and they are often associated with significant morbidity and mortality. The fetal cardiac axis, which indicates the orientation of the heart in relation to the chest wall, is formed by the angle between the anteroposterior axis of the chest and the interventricular septum of the heart. Studies conducted during the first trimester have demonstrated promising outcomes with respect to the applicability of cardiac axis measurement in fetuses with congenital heart defects as well as fetuses with extracardiac and chromosomal anomalies, which may result in improved health outcomes and reduced healthcare costs. The main aim of this review article was to highlight the cardiac axis as a reliable and powerful marker for the detection of congenital heart defects during early gestation, including defects that would otherwise remain undetectable through the conventional four-chamber view.

Nuchal Translucency and Congenital Heart Defects

Nuchal translucency comprises a temporary accumulation of fluid in the subcutaneous tissue on the back of a fetus's neck, which accompanies the crown-rump length and is observed through an ultrasound performed between 11 and 13 weeks + 6 days gestation. Nuchal translucency is considered to be above normal when values are higher than the 95th/99th percentile or equal to or higher than 2.5/3.5 mm. The first connection between increased nuchal translucency and the presence of congenital heart defects is described in the study of Hyett et al., who observed that they are directly proportional. Since that time, several studies have been conducted to understand if nuchal translucency measurements can be used for congenital heart defect screening in euploid fetuses. However, there is great variability in the estimated nuchal translucency cutoff values for congenital heart defect detection. The purpose of this review was to understand how increased nuchal translucency values and congenital heart defects are related and to identify which of these defects are more frequently associated with an increase in these values.

Efficacy of fetal cardiac axis evaluation in the first trimester as a screening tool for congenital heart defect or aneuploidy

Objective

To prove the efficacy of determining the abnormal fetal cardiac axis for screening congenital heart defects (CHDs) and predicting fetal aneuploidy at 11.0 to 13.6 weeks of pregnancy.

Methods

This retrospective study was performed at a single high-risk pregnancy center. The fetal cardiac axis was evaluated between 11.0 and 13.6 weeks of gestation in 142 fetuses. The cardiac axis in a 4-chamber view was measured as the angle between the line tracing the long axis of the heart and the line bisecting the thorax in the anteroposterior direction. A CHD was confirmed based on the second- to third-trimester fetal status or postnatal imaging. Aneuploidy was diagnosed using chorionic villus sampling, amniocentesis, or genetic testing after birth. Fisher's exact test was performed to assess the association between the fetal cardiac axis and the abnormal fetal status. A 2-way contingence table analysis was performed to confirm the efficacy of the fetal cardiac axis as a screening tool.

Results

Among the 142 fetuses, 10 had a CHD while 17 had aneuploidy. The abnormal fetal cardiac axis was significantly associated with CHDs (P=0.013) and aneuploidy (P=0.010). None of the fetuses with CHDs or aneuploidy had an isolated abnormal cardiac axis alone without other sonographic findings. The sensitivity of the fetal cardiac axis was 50.0% for CHDs and 41.2% for aneuploidy.

Conclusion

The fetal cardiac axis can be an additional helpful tool for prenatal screening of CHDs and aneuploidy in the first trimester.

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.

Pregnancy Outcome of Abnormal Nuchal Translucency: A Systematic Review

INTRODUCTION

Nuchal Translucency (NT) is the sonographic form of subcutaneous gathering of liquid behind the foetal neck in the first trimester of pregnancy. There is association of increased NT with chromosomal and non-chromosomal abnormalities.

AIM

The purpose of this systemic review was to review the pregnancy outcome of abnormal nuchal translucency.

MATERIALS AND METHODS

The present systematic review was conducted by searching English language articles from sources such as International Medical Sciences, Medline, Web of science, Scopus, Google Scholar, PubMed, Index Copernicus, DOAJ, EBSCO-CINAHL. Persian articles were searched from Iranmedex and SID sources. Related key words were "outcome", "pregnancy", "abnormal", and "Nuchal Translucency" (NT). All, randomized, descriptive, analytic-descriptive, case control study conducted during 1997-2015 were included.

RESULTS

Including duplicate articles, 95 related articles were found. After reviewing article titles, 30 unrelated article and abstracts were removed, and 65 articles were evaluated of which 30 articles were duplicate. Finally 22 articles were selected for final analysis. Exclusion criteria were, case studies and reports and quasi experimental designs. This evaluation has optioned negative relationship between nuchal translucency and pregnancy result. Rate of cardiac, chromosomal and other defects are correlated with increased NT≥2.5mm. Cardiac disease which were associated to the increased NT are heart murmur, systolic organic murmur, Atrial Septal Defect (ASD), Ventricular Septal Defect (VSD), tricuspid valve insufficiency and pulmonary valve insufficiency, Inferior Vena Cava (IVC) and Patent Ductus Arteriosus (PDA). The most common problems that related with increased NT were allergic symptoms.

CONCLUSION

According to this systematic review, increased NT is associated with various foetal defects. To verify the presence of malformations, birth defect consultations with a perinatologist and additional tests are required.

Fetal cardiac axis in non-anomalous pregnancies: does fetal gender or maternal body mass index (BMI) matter?

OBJECTIVES

To determine if cardiac axis obtained at an early ultrasound study (11-15 weeks) differs from that obtained at a late ultrasound study (18-22 weeks) in the same fetus and to evaluate the impact of fetal gender and/or maternal body mass index (BMI).

METHODS

Cardiac axes of 324 non-anomalous fetuses at 11-15 weeks gestation were measured, with follow-up measurements obtained at 18-22 weeks. Comparisons were performed based on gestational age period, fetal gender and obese/non-obese maternal status.

RESULTS

(1) Mean fetal cardiac axis did not change between 11 and 15 weeks; p = 0.8, (2) mean fetal cardiac axis was more levorotated at 11-15 weeks than measurements obtained at 18-22 weeks; 48.1 ± 7.1° versus 43.7 ± 8.9°; p < 0.0001, (3) male fetuses had less levorotated cardiac axis than female fetuses in late ultrasound studies but there was no difference between them at early ultrasound studies; 18-22 weeks male fetus, 42.7 ± 9.3° versus female fetus, 45.2 ± 8.3°; p = 0.02 and 11-15 weeks male fetus, 48.1 ± 7.0° versus female fetus, 48.4 ± 7.4°, p = 0.7, respectively, and (4) similar trends with the overall study population were observed in the comparison between fetuses of obese and non-obese women.

CONCLUSION

Fetal cardiac axis remains stable at 11-15 weeks, becoming less levorotated at 18-22 weeks. This may be attributed to increments in fetal lung volume. The differences in cardiac axis measurements between male and female fetuses examined at 18-22 weeks may also be attributable to differences in increment of fetal lung volume during this gestational age period.

Simplified first-trimester fetal cardiac screening (four chamber view and ventricular outflow tracts) in a low-risk population

OBJECTIVES

Our aim was to assess the accuracy of a simplified fetal cardiac study, inclusive of four-chamber view (4CV) and ventricular outflow tracts, performed during the 11-14 week screening by well-trained obstetricians to detect congenital heart diseases (CHDs).

METHODS

A transabdominal ultrasound was performed on 4820 singleton pregnant women at 11-14 weeks to visualize the visceral site, the 4CV, and the outflow tracts. Neonatal outcomes were recorded 6 and 12 months after birth.

RESULTS

Among the 4820 patients reviewed, 790 were excluded because of loss at prenatal or postnatal follow-up (649 cases), or inability to obtain adequate first-trimester sonographic cardiac evaluation (141 cases). Among the 4030 included cases, 32 CHD cases were detected (20 major and 12 minor); 18 of the major (90%) and five of the minor (42%) were detected or suspected in the first trimester, one major and six minor in the second trimester, and one major and one minor only after birth.

CONCLUSIONS

A simplified protocol is an effective tool to screen for CHD at 11-14 weeks.

Fetal heart defects: potential and pitfalls of first-trimester detection

Congenital heart defects (CHDs) are the leading cause of infant mortality due to birth defects. In the last 15 years, with the shift in screening for aneuploidies to the first trimester, extensive research has concentrated on early screening and detection of CHDs. Early detailed assessment of the fetal heart requires a high level of expertise in early anomaly scanning and fetal echocardiography. However, the detection of major CHDs at 11-13 weeks is influenced by their association with easily detectable markers, such as the nuchal translucency, ductus venosus blood flow and tricuspid regurgitation, and a policy decision as to the objectives of this scan and the allocation of resources necessary to achieve them. The use of transvaginal ultrasound and newer techniques are likely to improve the detection rate. However, the limitations of fetal echocardiography in the first trimester must be borne in mind, and follow-up at mid-gestational echocardiography is prudent in some cases.

Nuchal translucency and major congenital heart defects in fetuses with normal karyotype: a meta-analysis

OBJECTIVE

To pool published data regarding the sensitivity and specificity of nuchal translucency (NT) in the diagnosis of major congenital heart defects (CHDs) in fetuses with normal karyotype.

METHODS

MEDLINE and Scopus searches using combinations of the terms 'nuchal' and 'cardiac*' were complemented by perusal of references of the retrieved articles and an additional automated search using the 'search for related articles' function on PubMed. Only fetuses with normal karyotype and major CHDs were analyzed. Weighted estimates were made and summary receiver-operating characteristics curves were constructed.

RESULTS

The analysis included 20 studies (205 232 fetuses; 537 cases with major CHDs). The pooled sensitivity and specificity of NT > 95(th) centile for diagnosis of major CHDs was 44.4% (95% CI, 39.5-49.5) and 94.5% (95% CI, 94.4-94.6), respectively. The pooled sensitivity and specificity of NT > 99(th) centile was 19.5% (95% CI, 15.9-23.5) and 99.1% (95% CI, 99.1-99.2), respectively. For the subgroup of studies in which NT was measured by Fetal Medicine Foundation-certified operators, the pooled sensitivity and specificity of NT > 95(th) centile was 45.6% (95% CI, 39.6-51.7) and 94.7% (95% CI, 94.6-94.9), respectively. The corresponding estimates for NT > 99(th) centile were 21.0% (95%CI, 16.5-26.1) and 99.2% (95% CI, 99.2-99.3). The pooled positive likelihood ratio for NT > 99(th) centile was 30.5 (95% CI, 24.3-38.6). There was high across-studies heterogeneity for most estimates.

CONCLUSION

Approximately 44% of chromosomally normal fetuses with CHDs have NT > 95(th) centile and 20% have NT > 99(th) centile. However, there is high heterogeneity across studies, which largely remains even in subgroup analyses of studies of apparently similar design, potentially indicating the presence of some residual unidentified bias.

The current clinical aspects of idiopathic portal hypertension

IDIOPATHIC PORTAL HYPERTENSION (IPH) COMPRISES DISORDERS DEVELOPING INCREASED PORTAL PRESSURE IN THE ABSENCE OF CIRRHOSIS: the clear mechanisms to explain this disease are still not well recognized. IPH usually suggests a benign prognosis, but sometimes is complicated with severe hemorrhage due to ruptured esophageal varices, or massive splenomegaly. Conventional treatments for those complications for patients with cirrhosis usually works when diverted to patients with IPH, although some of those patients might require liver transplantation if the treatment fails. However, there are few consistent treatment strategies for IPH itself, its complications or the indications for liver transplantation. In this mini review, we summarize the clinical manifestations and several potential theories to explain the etiology, as well as the current treatment options for IPH.

Comparative studies of two dimensional and three dimensional ultrasonic nuchal translucency in trisomy assessments

Current two-dimensional (2D) ultrasonic marker measurements are inherent with intra- and inter-observer variability limitations. The objective of this paper is to investigate the performance of conventional 2D ultrasonic marker measurements and proposed programmable interactive three-dimensional (3D) marker evaluation. This is essentially important to analyze that the measurement on 3D volumetric measurement possesses higher impact and reproducibility vis-à-vis 2D measurement. Twenty three cases of prenatal ultrasound examination were obtained from collaborating hospital after Ethical Committee's approval. The measured 2D ultrasonic marker is Nuchal Translucency or commonly abbreviated as NT. Descriptive analysis of both 2D and 3D ultrasound measurement were calculated. Three trial measurements were taken for each method. Both data were tested with One-Sample Kolmogorov-Smirnov Test and results indicate that markers measurements were distributed normally with significant parametric values at 0.621 and 0.596 respectively. Computed mean and standard deviation for both measurement methods are 1.4495 ± 0.46490 (2D) and 1.3561 ± 0.50994 (3D). ANOVA test shows that computerized 3D measurements were found to be insignificantly different from the mean of conventional 2D at the significance level of 0.05. With Pearson's correlation coefficient value or R = 0.861, the result proves strong positive linear correlation between 2D and 3D ultrasonic measurements. Reproducibility and accuracy of 3D ultrasound in NT measurement was significantly increased compared with 2D B-mode ultrasound prenatal assessment. 3D reconstructed imaging has higher clinical values compare to 2D ultrasound images with less diagnostics information.

Early fetal echocardiography: ready for prime time?

The objective of this study was to examine the performance of early fetal echocardiography as a screening tool for major cardiac defects in a high-risk population. Fetal echocardiograms performed at 12 to 16 weeks were reviewed. Cases that did not undergo a follow-up echocardiogram at 18 to 22 weeks were excluded. Results of the early and follow-up echocardiograms were compared. Over a 4-year period, 119 early fetal echocardiograms were recorded. Of those, 81 (68%) had follow-up fetal echocardiograms. Results of the early echocardiogram were normal in 77 of 81 (95.1%) cases. Of these, the follow-up was normal in 75 of these 77 cases; in the remaining 2, the follow-up raised suspicion for a ventricular septal defect (VSD) in one and persistent left superior vena cava in the other. On the other hand, the early echocardiogram was abnormal in 4 (4.9%) cases: (1) atrioventricular canal defect, with the follow-up demonstrating a VSD; (2) hypoplastic right ventricle and transposition of the great arteries, confirmed on follow-up; (3) VSD and coarctation of the aorta, confirmed on follow-up. In the fourth case, the early echocardiogram suspected a VSD and right-left disproportion, yet the follow-up was normal. In conclusion, early fetal echocardiography appears to be a reasonable screening tool for major cardiac defects.

Additional first-trimester ultrasound markers

The first trimester (11-13 +6 weeks) ultrasound examination is useful for several reasons: determination of an accurate date of confinement, diagnostic purposes, and screening for fetal defects. Nuchal translucency measurement combined with maternal serum markers (free b-human chorionic gonadotropin and pregnancy-associated plasma protein A) is the mainstay of first-trimester screening for chromosomal defects. However, over the past decade additional ultrasound markers have been developed that improve the performance of this type of screening. The novel markers include evaluation of the nasal bone, fronto-maxillary angle measurement, and Doppler evaluations of the blood flow across the tricuspid valve and in the ductus venosus.

Nuchal translucency and cystic hygroma colli in screening for fetal major congenital heart defects in a series of 12,910 euploid pregnancies

OBJECTIVE

Many studies have shown that an increased nuchal translucency (NT) may be a good marker of fetal heart malformation, but the extent to which NT is suitable for identifying the population at risk remains unclear. We aimed to determine the value of NT measurement and of the presence of cystic hygroma colli in the screening of euploid fetuses for congenital heart defects (CHD).

METHODS

We carried out a retrospective analysis of 12 910 euploid pregnancies examined between January 1995 and August 2007 at our institution. The screening performance of NT measurements in identifying fetuses with CHD was assessed, with comparison between the use of cut-offs defined as absolute values, multiples of the median (MoM) and percentiles. The presence of cystic hygroma colli was also assessed in the prediction of CHD.

RESULTS

The incidence of major CHD was 3.4 per thousand (44/12 910). The sensitivity of NT measurement in screening for major CHD was 54.5% if the threshold was set at the 95(th) percentile, 45.4% if it was set at 3 mm, 27.3% for 3.5 mm, 50.0% for 1.5 MoM and 45.5% for 1.75 MoM. The false-positive rates for these thresholds were 8.4, 6.6, 1.7, 8.9 and 6.3%, respectively. The incidence of major CHD was 1.2% (10/813) in cases of thick NT (> 95(th) centile) and 4.3% (13/304) in cases of hygroma colli.

CONCLUSIONS

NT measurement during the first trimester is potentially useful for screening for fetal major CHD. Screening performance is consistent whether NT values are expressed as MoMs, percentiles or absolute values. The incidence of major CHD seems to be higher in cases of cystic hygroma colli.

Fetal thickened nuchal soft tissues may first appear in the second trimester in Down syndrome

PURPOSE

To describe a series of cases of late-onset fetal nuchal translucency in Down syndrome.

METHOD

In our practice area, most pregnant women usually undergo 3 different sonographic examinations: a fetal nuchal translucency examination in the 1st trimester and 2 detailed surveys of all fetal organs in the early 2nd trimester and in midpregnancy.

RESULT

During the study period (2003-2008), we detected 11 fetuses with new appearance of severe thickened nuchal soft tissues (>or=6 mm) at 14-16 weeks' gestation after a normal nuchal screening in the 1st trimester. All of these fetuses had trisomy 21. Associated structural anomalies were observed in 10/11 of the cases. In addition, there were 12 fetuses with new appearance of thickened nuchal soft tissues (<4 mm); all these fetuses had a normal karyotype and were normal at delivery.

CONCLUSION

Obstetricians should be aware that a nuchal abnormality may first appear only at 14-16 weeks' gestation. Fetal karyotyping is advocated in these cases because of the high probability of Down syndrome.

First Trimester Ultrasound Screening: An Update

For many years, the main use of ultrasound in the first trimester of pregnancy was to confirm viability and to establish gestational age. Indeed, the crown-rump length measurement in the first trimester remains the most accurate method to estimate the gestational age even today. However, improvements in ultrasound equipment and improvement in our understanding of normal and abnormal fetal development allows us now to perform a much more complete first trimester fetal evaluation. This pertains not only to the diagnosis of fetal anomalies but also to screening for fetal defects. The combination of the nuchal translucency measurement and maternal serum biochemistries (free β-hCG and PAPP-A) has been shown to be an extremely efficient way to screen for fetal aneuploidy. The addition of other first trimester markers such as the nasal bone evaluation, frontomaxillary facial angle measurement, and Doppler evaluation of blood flow across the tricuspid valve and through the ductus venosus improves the screening performance even further by increasing the detection rates and decreasing the false positive rates. Several of the first trimester markers also are useful in screening for cardiac defects. Furthermore, significant nuchal translucency thickening has been associated with a variety of genetic and nongenetic syndromes. A recently described first trimester marker called the intracerebral translucency appears to hold great promise in screening for open spine defects. Finally, it appears that a first trimester evaluation (uterine artery Doppler and the measurement of certain biochemical markers in the maternal serum) significantly improves the assessment of the risk of preeclampsia.

The nuchal translucency and the fetal heart: a literature review

In this overview the current knowledge of the relationship between an increased nuchal translucency (NT) measurement and fetal heart structure and function in chromosomally normal fetuses is reviewed. Relevant pathophysiological theories behind the increased NT are discussed. Fetuses with an increased NT have an increased risk for congenital heart disease (CHD) with no particular bias for one form of CHD over another. This risk increases with increasing NT measurement. Although the NT measurement is only a modestly effective screening tool for all CHD when used alone, it may indeed be effective in identifying specific CHD "likely to benefit" from prenatal diagnosis. The combination of an increased NT, tricuspid regurgitation and an abnormal ductus venosus (DV) Doppler flow profile, is a strong marker for CHD. A fetal echocardiogram should be performed at 20 weeks' gestation in fetuses with an NT > or = 95th percentile but < 99th percentile. When the NT measurement is > or = 99th percentile, or when tricuspid regurgitation and/or an abnormal DV flow pattern is found along with the increased NT, an earlier echocardiogram is indicated, followed by a repeat scan at around 20 weeks' gestation. The resultant increased demand for early fetal echocardiography and sonographers with this special expertise needs to be planned and provided for.

Risk assessment of trisomy 21 by maternal age and fetal nuchal translucency thickness in 7,096 unselected pregnancies in Slovenia

AIM

To evaluate the screening for trisomy 21 by maternal age and nuchal translucency in a low-risk population.

METHODS

Screening was performed in 7,096 singleton pregnancies. The estimated risk for trisomy 21, the detection rate (DR), false positive rate (FPR) and the cut-off nuchal translucency thickness to obtain a 5% FPR were calculated.

RESULTS

The median maternal age was 28.6 years. The estimated risk for trisomy 21 was 1 in 300 or greater in 2.4% (171 of 7,096) of all pregnancies and in 75% (9 of 12) of trisomy 21 pregnancies. The DR for all aneuploidies was 83.3%, and 75% for trisomy 21. The estimated FPR at risk 1 in 300 for the whole population in 2004 was 3.8%. It is predicted to remain below 4% at least until 2007; to achieve a 5% FPR in 2007 the risk limit 1 in 400 is proposed.

CONCLUSIONS

Screening for trisomy 21 in a low-risk population in Slovenia gives comparable results to those in other countries. The only result that varies is the percentage of screen positive patients at the risk limit 1 in 300. We believe the risk limit should be specifically estimated for each country based on its population distribution of maternal age.

First trimester ultrasonography in screening and detection of fetal anomalies

An obstetrical ultrasound examination provides invaluable information regarding the fetus. Until the mid-1980s, ultrasound in the first trimester was limited to localization of the pregnancy, establishing viability, and accurate dating. With the advent of high-resolution ultrasound and transvaginal scanning, a significant amount of information about the fetus can be gained and provided to the patient at a very early stage in gestation. This article provides an overview of the role of first trimester (11-13 + 6 weeks' gestation) ultrasound in screening and diagnosis of fetal anomalies. The first trimester is an ideal time for screening for aneuploidy, primarily due to the advantages that nuchal translucency (NT) measurement provides. NT measurement is also useful in establishing the risk of congenital cardiac disorders and a number of genetic and non-genetic syndromes. Significant NT thickening is associated with an increase in perinatal morbidity and mortality. Potential mechanisms resulting in increased NT are discussed. A number of new ultrasound markers for fetal aneuploidy have been investigated over the past several years, some of which appear to improve the screening efficacy of early ultrasonography. The role of these is reviewed. A number of fetal anomalies can now be consistently diagnosed in the first trimester. Their appearance at this early gestational age is discussed as well. It is clear that, data obtained by first trimester ultrasound are useful in counseling expectant parents and in planning the appropriate follow-up.

Fetal echocardiography at the time of the nuchal translucency scan

OBJECTIVE

The fetal heart is not studied routinely in the first trimester because of technical and time limitations. Our aim was to assess the feasibility of performing a fetal cardiac study in pregnancies referred for nuchal translucency (NT) screening, using high-frequency linear transabdominal transducers with a specific ultrasound preset.

METHODS

A single trained operator assessed the fetal heart in pregnancies with a fetal crown-rump length (CRL) of 60-84 mm that had been referred for NT screening. A 15- or 6-MHz transabdominal linear transducer with a specific preset suitable mainly for color-flow mapping was used to confirm or refute normal cardiac anatomy rather than to establish a specific diagnosis. Fetuses having an increased risk for congenital heart disease were referred to a tertiary center for a further examination within 1 week. This group consisted of all fetuses with NT > 95(th) centile and those in which a family history or the initial heart scan increased the risk.

RESULTS

A total of 608 fetuses with a median CRL of 65 mm was examined between 2003 and 2005. A cardiac scan was performed successfully in 456 (75%) using a 15-MHz linear transducer alone, and the additional use of a 6-MHz transducer allowed diagnostic images to be obtained in a further 152. Normal cardiac anatomy was assessed confidently within 10 min in 517/608 (85%) pregnancies; in 85 (14%) a longer time was needed and six patients were rescheduled within 2 weeks because of non-diagnostic images at the initial scan. In 571/608 (94%) the risk for congenital heart disease (CHD) was not increased and the heart was considered normal at initial echocardiography; this was confirmed by later scans and at postnatal follow-up. In 37/608 (6%) fetuses the risk for CHD was increased (35 for NT > 95(th) centile and two for family history). In this group normal heart anatomy was described in 34 fetuses and confirmed by subsequent specialist echocardiography. Cardiac defects were suspected in three fetuses (all with increased NT) and confirmed by a fetal cardiologist in each case.

CONCLUSIONS

A trained operator can perform a fetal heart study during the NT screening test using transabdominal high-resolution transducers in an acceptable length of time.

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.

Nuchal translucency measurement and congenital heart defects: modest association in low-risk pregnancies

OBJECTIVE

To assess the performance of nuchal translucency (NT) measurement in the first trimester of pregnancy as a marker for congenital heart defects (CHD) in the fetus in a low-risk obstetric population.

METHODS

Nuchal translucency screening was offered over a 3-year period to consecutive pregnant women without known a priori risk factors and attending midwife practices in three different areas in the Netherlands. In chromosomally normal fetuses and infants from the study population the NT measurements were matched with CHD detected either prenatally or postnatally.

RESULTS

NT screening was offered to 6132 women with an uptake of 83%. A total of 4876 NT measurements was performed. Pregnancy outcome data were available in 4181 cases (86%). Defects of the heart and great arteries (CHD) were diagnosed in 24 cases (prevalence 5.8/1000). Thirteen of these were classified as major (prevalence 3.1/1000). Two major CHD occurred in fetuses showing an increased NT at the first-trimester scan. The sensitivity of NT measurement > 95th and > 99th percentile for all CHD and for major CHD, was 8% and 15%, respectively. The positive likelihood ratios of NT > 95(th) and > 99th percentile for major CHD were 6, 5 and 33, respectively.

CONCLUSION

In pregnancies without known risk factors also, an increased NT is associated with major cardiac defects in the fetus and therefore represents an indication for specialized fetal echocardiography. However, this association is too weak to envisage a role for NT measurement as single screening strategy for the prenatal detection of cardiac defects.

First Trimester Down’s Syndrome Screening Shows High Detection Rate for Trisomy 21, but Poor Performance in Structural Abnormalities – Regional Outcome Results

OBJECTIVE

To evaluate whether first trimester screening markers are altered in pregnancies affected both by other chromosomal defects than trisomy 21 and structural anomalies and whether it is possible to detect these pregnancies by combined ultrasound and biochemical screening test.

METHODS

Altogether 4,776 singleton pregnancies underwent first trimester screening. Of them, 3,101 women were screened using a combination of maternal serum free hCG, pregnancy-associated plasma protein A and nuchal translucency and 1,361 women with first trimester biochemistry without ultrasound. Nuchal translucency screening was performed between the 11th and 13+6th gestational weeks, and biochemistry 1-2 weeks earlier.

RESULTS

Using a fixed cut-off rate of 1:250 for Down's syndrome, the detection rate of trisomies 21, 18 and 13 were 92, 67 and 0%, respectively. All open defects, 85% of cardiac defects and other minor defects were not detected in first trimester screening. Majority of these structural abnormalities occurred in women under 35 years of age.

CONCLUSION

First trimester Down's syndrome screening is effective in trisomy screening, but its performance in structural abnormalities is low, when used as a part of routine clinical practice. We conclude that it is too early to drop second trimester screening ultrasound entirely from antenatal care programs if a high detection rate is to be achieved also in structural defects.

Is measurement of nuchal translucency thickness a useful screening tool for heart defects? A study of 16,383 fetuses

OBJECTIVE

To determine the performance of nuchal translucency thickness (NT) measurement as a screening method for congenital heart defects (CHD) among fetuses with normal karyotype.

METHODS

An NT measurement was made in 16 383 consecutive euploid fetuses derived from an unselected pregnant population. The cut-offs for increased risk of heart defects, chosen a priori and tested prospectively, were: NT >or= 95th centile for crown-rump length, NT >or= 3 mm, and NT >or= 3.5 mm. The sensitivity and false-positive rate (FPR; 1 minus specificity) of the risk cut-offs and their positive and negative likelihood ratios (+LR and -LR) with regard to CHD were calculated.

RESULTS

Among the 16 383 fetuses with an NT measurement there were 127 cases with a diagnosis of heart defect confirmed by cardiac investigations after birth or at autopsy. Of these, 55 defects were defined as major, of which 52 were isolated (no other defects or chromosomal aberrations), corresponding to a prevalence of major heart defects in chromosomally normal fetuses/newborns of 3.3/1000. The sensitivity, FPR, +LR and -LR for NT >or= 95th centile with regard to an isolated major heart defect were: 13.5%, 2.6%, 5.2 and 0.9, respectively. For NT >or= 3.0 mm these values were: 9.6%, 0.8%, 12.0 and 0.9, and for NT >or= 3.5 mm they were: 5.8%, 0.3%, 19.3 and 0.9.

CONCLUSIONS

NT measurement is a poor screening method for isolated major CHD. A method with a much higher detection rate and with a reasonably low FPR is needed. However, increased NT indicates increased risk of fetal heart defect, and women carrying fetuses with increased NT should be offered fetal echocardiography in the second trimester.

Prenatal detection of heart defects in a non-selected population of 30,149 fetuses--detection rates and outcome

OBJECTIVES

To evaluate the detection rate of congenital heart defects (CHD) in a non-selected population and to follow outcome after diagnosis.

METHODS

All 30,149 fetuses/newborns that were scheduled to deliver at our hospital between February 1991 and December 2001 were registered prospectively. Of these, 29,460 (98%) fetuses had a prenatal ultrasound scan at our center. The routine fetal examination at approximately 18 weeks' gestation included the four-chamber view and the great arteries of the fetal heart. The follow-up period was 2-13 years.

RESULTS

Of 97 major CHDs, 55 (57%) were detected prenatally, 16% (9/55) prior to, 66% (36/55) at and 18% (10/55) after the routine scan. Forty-four percent (19/43) of the isolated CHDs, 67% (36/54) of those with associated malformations and 48% (11/23) of the isolated ductal-dependent CHDs were detected. Thirty-eight percent (37/97) had an abnormal karyotype. Of the 55 major CHDs detected, 44% (24) of the pregnancies with lethal/serious fetal malformations were terminated, 15% (8) died in utero, 42% (23) were born alive and 27% (15) were still alive after 2 years. Of the 42 CHDs detected postnatally, 2% (1) were terminated for other reasons, 98% (41) were born alive and 81% (34) were still alive after 2 years.

CONCLUSIONS

Prenatal detection of CHD is still a challenge, with a 57% detection rate only. Isolated defects are detected less frequently. The overall outcome suggests that the most severe defects are detected with the present screening setting; only 27% of the babies with major CHDs detected were still alive after 2 years. Data from long-term follow-up will be of importance for the counseling process.

Threshold of nuchal translucency for the detection of chromosomal aberration: comparison of different cut-offs

This study evaluated the sensitivities and false positive rates of the screening test using ultrasonographic measurement of thickness of nuchal translucency (NT) with different cut-offs for chromosomal aberration in a Korean population. We included 2,570 singleton pregnancies undergoing ultrasound between 11 weeks and 14 weeks of gestation in this study. We analyzed the sensitivities of NT alone for screening chromosomal aberration using three cut-offs -2.5 mm, 3.0 mm, and 95th percentile for each crown rump length (CRL). There were 31 chromosomal aberrations (1.2%) including 12 cases of trisomy 21. The numbers of chromosomal aberrations that were detected by NT with different cut-offs of 2.5 mm, 3.0 mm and the 95th percentile CRL were 22, 18 and 23, respectively. At a threshold of 2.5 mm, the sensitivity and the false positive rate for total chromosomal aberrations were 67.7% and 6.3%, respectively. At 3.0 mm, those were 54.8% and 3.5%, respectively. At the 95th percentile CRL, those were 70.9% and 5.8%, respectively. The use of CRL-dependent cut-offs for nuchal translucency improves the detection of chromosomal aberrations when compared to fixed cut-offs in a Korean population.

[Down syndrome screening by ultrasound]

The nuchal translucency is the usual subcutaneous space, between the skin and the soft tissues covering the fetus'neck spine, observed by ultrasound during the first trimester of pregnancy. It increases with gestational age. The association between nuchal translucency thickness and risk of Down syndrome was firstly observed in high risk populations as an old maternal age or a history of a previous child affected by Down syndrome. However, these studies are retrospective and only report the issue among pregnancies associated with an abnormal nuchal translucency thickness. Furthermore, as the performance of a screening test is correlated to the prevalence of the disease in the studied population, such results can not be extrapolated to the general population. To date, eleven prospective studies have been published, assessing the performance of the nuchal translucency measurement in a general population, including about 125,000 patients. The global sensitivity of this screening was 70% for a false positive rate of 5%. For an adjusted risk on the maternal age, the detection rate increased up to 77%. Although nuchal translucency measurement is an early and performing screening tool, uncertainties remain nevertheless about its reproducibility in the general population. In order to correctly measure the nuchal translucency, a previous training course is necessary to guarantee adequate and reproducible measurements.

Targeted mid-trimester ultrasound examination: how does fetal anatomic visualization depend upon the duration of the scan?

OBJECTIVE

To determine the relationship between visualization of key fetal anatomic structures during mid-trimester ultrasound examination with gestational age and duration of examination.

METHODS

One hundred ultrasound examinations at 16-22 weeks' gestation were reviewed to determine the times at which key fetal anatomic features were seen. Scans were terminated at 30 min or when a comprehensive anatomic survey was complete. Exclusion criteria included multiple gestation, maternal weight>77 kg, abdominal wall scarring, and suspected fetal anomalies.

RESULTS

Visualization of cranial anatomy including lips, face, midline, ventricles, choroid plexus, and cerebellum was achieved in 98% of patients within 30 min. The corresponding figures for spine, cardiac screening (four-chamber, aortic, and pulmonary outflow views) and for abdominal anatomy (stomach, kidneys, bladder, ventral wall, and three-vessel cord) were 91%, 91%, and 99%, respectively. A complete anatomic survey including each of the above elements was obtained by 10, 15, 20, 25, and 30 min in 8%, 31%, 53%, 72% and 81% of the subjects. Rates of complete anatomic surveys within 30 min improved by gestational age interval, from 20/30 (67%) at 16-18 weeks, to 36/44 (82%) at 18-20 weeks, and 25/26 (96%) at 20-22 weeks; this rise was primarily due to improvements in visualization of the spine and heart.

CONCLUSIONS

A comprehensive anatomical survey can be completed in 10 min or less in a minority of patients. For each 5-min time increment up to 30 min, the rate of complete surveys improves. Rates of completed anatomic surveys rise with gestational age.

Elevated first-trimester nuchal translucency increases the risk of congenital heart defects

OBJECTIVE

We sought to evaluate the association between first trimester nuchal translucency measurement and the risk for major congenital heart defect in chromosomally normal fetuses.

STUDY DESIGN

First trimester (10 weeks 4 days of gestation to 13 weeks 6 days of gestation) nuchal translucency was obtained in a large prospective multicenter National Institute of Child Health and Human Development study for Down syndrome prediction. The study, which was conducted between May 1998 and December 2000, was restricted to singleton pregnancies. Gestational age was determined by crown rump length measurements. Perinatal outcomes were determined and included the frequency of major congenital heart defect, which was defined as those cases that potentially could require surgery, intensive medical therapy, or prolonged follow-up time. Logistic regression analysis was used to determine whether nuchal translucency was a significant predictor of congenital heart defect.

RESULTS

There were 8167 chromosomally normal pregnancies, of which 21 cases of major congenital heart defect were identified at follow-up examination (incidence, 2.6/1000 pregnancies). The risk of congenital heart defect rose with increasing nuchal translucency measurements. The mean nuchal translucency value for the normal and congenital heart defect groups were 1.5 mm and 1.9 mm, respectively (P = .05). With a nuchal translucency measurement of < 2.0 mm, the incidence of congenital heart defect was 13 of 6757 pregnancies (1.9 of every 1000 pregnancies). At 2.0 to 2.4 mm, the incidence was 5 of 1032 pregnancies (4.8 of every 1000 pregnancies). At 2.5 to 3.4 mm, the incidence was 2 of 335 pregnancies (6.0 of every 1000 pregnancies). At > or = 3.5 mm, the incidence was 1 of 43 pregnancies (23 of every 1000 pregnancies). Logistic regression analysis confirmed that nuchal translucency was associated significantly with congenital heart defect (odds ratio, 2.1; 95% CI, 1.4-3.1; P = .0004).

CONCLUSION

Increased first trimester nuchal translucency measurement was associated with a higher risk of major congenital heart defect in chromosomally normal pregnancies. The practical implications of our findings are that patients with unexplained elevations of nuchal translucency may need referral for a fetal echocardiogram.

[Screening of chromosome anomalies during the first trimester]

In view of today's knowledge, it is evident that a very efficient screening for chromosome anomalies can be carried out during the first trimester. Prospective studies of a total of 200,868 pregnancies-among them 871 fetuses with trisomy 21-have shown that measuring the nuchal transparency can identify 76.8% of fetuses with trisomy 21, with a false-positive rate of 4.2%. If the measurement of nuchal transparency is combined with that of the maternal serum concentrations of free human beta-choriogonadotropin and pregnancy-associated plasma A, the detection rate is 87.0% with a false-positive rate of 5% (prospective studies of altogether 44,630 pregnancies with 215 fetuses suffering from trisomy 21). At present, further signs of Down syndrome in the first trimester are being investigated, such as the missing fetal nasal bone, the maxilla and the blood flow pattern in the ductus venosus. Well-known signs of trisomy 13 and 18, which are already visible in the first trimester, are megacystis, omphalocele, polydactyly and holoprosencephaly. Most pregnant women prefer being screened during the first instead of the second trimester. Therefore every expectant mother should be offered an appropriate examination during the first trimester. It is essential for the effectiveness of the screening that the examiners be suitably trained and that the results of the ultrasound and laboratory examinations be subjected to a regular external quality control. In Austria, there is a general consent to follow the guidelines of the Fetal Medicine Foundation.

Increased nuchal translucency with normal karyotype

Increased fetal nuchal translucency (NT) thickness between 11 and 14 weeks' gestation is a common phenotypic expression of chromosomal abnormalities, including trisomy 21. However, even in the absence of aneuploidy, nuchal thickening is clinically relevant because it is associated with an increase in adverse perinatal outcome caused by a variety of fetal malformations, dysplasias, deformations, dysruptions, and genetic syndromes. Once the presence of aneuploidy is ruled out, the risk of perinatal outcome dose not statistically increase until the nuchal translucency measurement reaches 3.5 mm or more (>99th percentile). This increase in risk occurs in an exponential fashion as the NT measurement increases. However, if the fetus survives until midgestation, and if a targeted ultrasound at 20 to 22 weeks fails to reveal any abnormalities, the risk of an adverse perinatal outcome and postnatal developmental delay is not statistically increased.

Improved first-trimester Down syndrome screening performance by lowering the false-positive rate: a prospective study of 9941 low-risk women

OBJECTIVE

To determine the performance of screening for Down syndrome (DS) and other major chromosomal abnormalities using nuchal translucency (NT), free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) in a prospective study of a non-selected population.

METHODS

Of 9941 women with an early ultrasound examination, NT was measured in 8622 singleton pregnancies with a gestational age between 10 + 3 and 13 + 6 weeks. beta-hCG and PAPP-A were analyzed in 6441 cases. Detection rates (DR) and false-positive rates (FPR) for the NT screening, the double test (beta-hCG and PAPP-A) and the combined test (NT and the double test) were calculated using a 1 : 250 cut-off.

RESULTS

NT could be measured in 97.5% of cases. The DR for DS with NT screening alone was 75% with a FPR of only 1.8%. The double test detected 73% and the combined test 91%, for FPRs of 8.8% and 2.1%, respectively. We detected 80% of fetuses with other major chromosomal abnormalities with a combination of NT screening and other ultrasound findings. Low beta-hCG and PAPP-A values (below 0.4 MoM) were observed in 0.5% of the women including all cases of triploidy and trisomy 18 and 13.

CONCLUSIONS

The performance of a screening strategy for DS using a combination of NT and the double test was superior to that using either NT or the double test alone due to a very low FPR and a higher DR.

Prenatal diagnosis ofde novo proximal interstitial deletion of 9q and review of the literature of uncommon aneuploidies associated with increased nuchal translucency

OBJECTIVES

To present the prenatal diagnosis and molecular cytogenetic analysis of de novo proximal interstitial deletion of 9q and to review the literature of uncommon aneuploidies associated with increased nuchal translucency (NT).

CASE

Obstetric ultrasound at 11 weeks' gestation revealed an increased NT thickness of 6.6 mm in a 31-year-old primigravid woman. At 13 weeks' gestation, repeat ultrasound examinations revealed a normal NT thickness of 1.8 mm. The subcutaneous nuchal fluid accumulation was no longer present at the following ultrasound scans. An amniocentesis was performed at 18 weeks' gestation.

RESULTS

Cytogenetic analysis revealed a karyotype of 46,XX,del(9)(q21.1q22.2). The parental karyotypes were normal. At 21 weeks' gestation, a 442-g female fetus was delivered with low-set ears, hypertelorism, and a thick nuchal fold. The parental origin of the interstitial deletion of 9q was analyzed with polymorphic DNA markers. With the microsatellite markers D9S238 (9q13), D9S889 (9q21.11), and D9S253 (9q22.2), two alleles inherited from the parents were seen in the proband, but with markers D9S1780 (9q21.31), D9S303 (9q21.32), D9S252 (9q21.33), and D9S316 (9q22.1), only one maternal allele was present. The deletion was of paternal origin.

CONCLUSIONS

Fetuses with uncommon aneuploidies may manifest increased NT in the first trimester. The present case provides evidence for a correlation between increased NT and interstitial 9q deletion. Prenatal identification of increased NT should alert subtle structural chromosome aberrations and prompt high-resolution karyotyping.

Nuchal translucency and fetal cardiac defects: a pooled analysis of major fetal echocardiography centers

OBJECTIVE

Increased fetal nuchal translucency is associated with increased risk for congenital heart defects. In the present study, we aimed to investigate whether fetal nuchal translucency distribution differs among different types of congenital heart defects and whether it can lead to an earlier diagnosis.

STUDY DESIGN

Four fetal echocardiography units provided data on fetuses with a congenital heart defect diagnosis in whom nuchal translucency thickness had been measured in the first trimester. Nuchal translucency data were compared per chromosomal status and type of congenital heart defect. Data on gestational age at diagnosis were also analyzed.

RESULTS

Six hundred thirty-seven cases of congenital heart defect with known karyotype and exact nuchal translucency measurements were analyzed. Nuchal translucency was > or =3.5 mm in 22.9% of chromosomally normal fetuses (n = 397) and 58.8% of chromosomally abnormal cases (n = 240). Among fetuses with normal karyotype, the proportion of cases of congenital heart defect with increased nuchal translucency was similar in each of the subtypes of congenital heart defect (P = .96). Mean gestational age at diagnosis of congenital heart defect in fetuses with normal karyotype was 22.1 weeks with nuchal translucency of <3.5 mm and 16.1 weeks with nuchal translucency of > or =3.5 mm.

CONCLUSION

Finding nuchal translucency of > or =3.5 mm may lead to an earlier diagnosis of all major types of congenital heart defects.

First-trimester screening for aneuploidy

Prenatal screening for aneuploidy in the first trimester using novel ultrasound and maternal serum markers represents a promising improvement over the currently available second-trimester screening methods. This article reviews the current status of first-trimester screening for Down syndrome and other aneuploidies and explores the issues related to implementing first-trimester screening into mainstream prenatal care in the United States.

Fetal cardiac defects and increased nuchal translucency thickness: a prospective study

OBJECTIVE

The purpose of this study was to examine prospectively the association between increased nuchal translucency thickness and major cardiac defects in chromosomally normal fetuses.

STUDY DESIGN

A prospective cohort study of 263 chromosomally normal fetuses with an increased nuchal translucency thickness at 11 to 14 weeks of gestation at a tertiary referral center was performed. The incidence of major cardiac defects was examined in relation to the fetal nuchal translucency thickness at the 11 to 14 week ultrasound examination.

RESULTS

The nuchal translucency thickness measurements ranged from 2.2 to 8.0 mm (median, 3.1 mm). There were 13 cases of major cardiac defects in this cohort, which gave a prevalence of 49.4 of every 1000 fetuses. With the use of the 99th percentile of nuchal translucency thickness, the prevalence rose to 106.7 of every 1000 fetuses.

CONCLUSION

In this population of chromosomally normal fetuses with an increased nuchal translucency thickness, the incidence of cardiac defects was high, which suggests that fetal echocardiography is indicated in this group.

Population genetic screening programmes: principles, techniques, practices, and policies

This paper examines the professional and scientific views on the principles, techniques, practices, and policies that impact on the population genetic screening programmes in Europe. This paper focuses on the issues surrounding potential screening programmes, which require further discussion before their introduction. It aims to increase, among the health-care professions and health policy-makers, awareness of the potential screening programmes as an issue of increasing concern to public health. The methods comprised primarily the review of the existing professional guidelines, regulatory frameworks and other documents related to population genetic screening programmes in Europe. Then, the questions that need debate, in regard to different types of genetic screening before and after birth, were examined. Screening for conditions such as cystic fibrosis, Duchenne muscular dystrophy, familial hypercholesterolemia, fragile X syndrome, hemochromatosis, and cancer susceptibility was discussed. Special issues related to genetic screening were also examined, such as informed consent, family aspects, commercialization, the players on the scene and monitoring genetic screening programmes. Afterwards, these questions were debated by 51 experts from 15 European countries during an international workshop organized by the European Society of Human Genetics Public and Professional Policy Committee in Amsterdam, The Netherlands, 19-20, November, 1999. Arguments for and against starting screening programmes have been put forward. It has been questioned whether genetic screening differs from other types of screening and testing in terms of ethical issues. The general impression on the future of genetic screening is that one wants to 'proceed with caution', with more active impetus from the side of patients' organizations and more reluctance from the policy-makers. The latter try to obviate the potential problems about the abortion and eugenics issues that might be perceived as a greater problem than it is in reality. However, it seems important to maintain a balance between a 'professional duty of care' and 'personal autonomy'.

Nuchal translucency and other first-trimester sonographic markers of chromosomal abnormalities

There is extensive evidence that effective screening for major chromosomal abnormalities can be provided in the first trimester of pregnancy. Prospective studies in a total of 200,868 pregnancies, including 871 fetuses with trisomy 21, have demonstrated that increased nuchal translucency can identify 76.8% of fetuses with trisomy 21, which represents a false-positive rate of 4.2%. When fetal nuchal translucency was combined with maternal serum free-beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A in prospective studies in a total of 44,613 pregnancies, including 215 fetuses with trisomy 21, the detection rate was 87.0% for a false-positive rate of 5.0%. Studies from specialist centers with 15,822 pregnancies, which included 397 fetuses with trisomy 21, have demonstrated that the absence of the nasal bone can identify 69.0% of trisomy 21 fetuses, which represents a false-positive rate of 1.4%. It has been estimated that first-trimester screening by a combination of sonography and maternal serum testing can identify 97% of trisomy 21 fetuses, which represents a false-positive rate of 5%, or that the detection rate can be 91%, which represents a false-positive rate of 0.5%. In addition to increased nuchal translucency, important sonographic markers for chromosomal abnormalities, include fetal growth restriction, tachycardia, abnormal flow in the ductus venosus, megacystis, exomphalos and single umbilical artery. Most pregnant women prefer screening in the first, rather than in the second, trimester. As with all aspects of good clinical practice, those care givers who perform first-trimester screening should be trained appropriately, and their results should be subjected to external quality assurance.

The influence of image magnification in first-trimester screening for Down syndrome by fetal nuchal translucency in Asians

OBJECTIVE

The aim of this prospective study was to evaluate the impact of image magnification in the measurements of crown-rump length (CRL) and nuchal translucency (NT) thickness for first-trimester Down syndrome screening in Asians.

METHODS

Ultrasound measurements of NT and CRL were performed in 561 consecutive Taiwanese unaffected fetuses and 11 cases of Down syndrome fetuses between 12 and 14 weeks of gestation. All sonographic images were measured by one qualified examiner to prospectively undergo first-trimester NT screening for Down syndrome. Fetal CRL and NT thickness were measured on three separated images including the original image, regular image, and the magnified image.

RESULTS

A significant mean difference (0.59 +/- 4.24 mm) of CRL was found between measurements on the original and regular image (p < 0.001). There was a significant mean difference of NT thickness measurements between the regular and magnified image (0.12 +/- 0.25 mm, p < 0.001). Seven out of the 11 cases (63.6%) of Down syndrome with NT thickness > or =2.5 mm was measured on three separated images. A significantly reduced incidence of NT thickness > or =2.5 mm on the magnified image was noted than those of the original and regular image measurements in unaffected cases (p < 0.001). Either using the assessing method by the 95th centile cutoff value of NT thickness or combined risk, our results could achieve observed detection rate of 63.6% measured on three separated images.

CONCLUSIONS

Our data indicate that the image magnification could reduce the false-positive rate by using a fixed cutoff value of NT thickness, but would have no influence on the results when using the assessing method either by the 95th centile cutoff value of NT thickness or the combined risk. In order to place the caliper more accurately, a magnified image should be recommended as a standard image in the measurements of the NT thickness.

Does nuchal translucency have a role in fetal cardiac screening?

Increased nuchal translucency is the strongest single marker for chromosomal abnormality. Consequently, it is currently becoming established as the foundation of most early screening programmes for Down syndrome. In the absence of chromosomal abnormality, increased nuchal translucency has been shown to be associated with other congenital anomalies including cardiac defects. Several datasets have now reported this association and here these are reviewed to assess the effectiveness of nuchal translucency measurement as a screening tool for the prenatal detection of congenital heart disease.