First-trimester diagnosis of nuchal anomalies: significance and fetal outcome

Application of chromosome microarray analysis and karyotyping in diagnostic assessment of abnormal Down syndrome screening results

Background

Down syndrome (DS) is the most common congenital cause of intellectual disability and also leads to numerous metabolic and structural problems. This study aims to explore the application value of chromosomal microarray analysis (CMA) and karyotyping in prenatal diagnosis for pregnant women with abnormal DS screening results.

Methods

The study recruited 1452 pregnant women with abnormal DS screening results including 493 with an enlarged nuchal translucency thickness (NT ≥ 2.5 mm) and 959 with an abnormal second-trimester maternal serum biomarker screening results. They underwent amniocentesis to obtain amniotic fluid for CMA and karyotyping.

Results

CMA identified 74/1452 abnormal results, which was more efficient than karyotyping (51/1452, P < 0.05.) CMA is equivalent to traditional karyotyping for identifying aneuploidies. Compared to karyotyping CMA identified 1.90% more copy number variants (CNVs) ranging from 159Kb to 6496Kb. However, 34.4% of them were recurrent pathogenic CNVs associated with risk of neurodevelopmental disorders. CMA identified 13 variants of uncertain significance (VUS) results and 1 maternal uniparental disomy (UPD) of chromosome 7. Karyotyping identified 3 mosaic sex chromosome aneuploidy and 4 balanced translocation which could not be identified by CMA. In enlarged NT group, karyotyping identified 80.9% abnormal results while in serum screening group karyotyping identified 35.7%. However, the incidence of pathogenic/likely pathogenic (P/LP) CNVs was nearly the same in both groups. That was because aneuploidies and gross duplication/deletion were previously screened out by NT scan.

Conclusions

CMA and karyotyping have both advantages and disadvantages in prenatal diagnosis of pregnant women with abnormal DS screening results. However, there was not enough evidence to support routine CMA in pregnant women with abnormal DS screening results.

Outcome of antenatally diagnosed cystic hygroma - Lessons learnt

PURPOSE

This study is carried out to characterize the prognosis and outcome of antenatally diagnosed cystic hygroma in a series of registered pregnancies.

METHODS

This is a prospective cohort study, carried out over a period of 4 years (Jan 2016-Sept 2019). All the pregnancies referred from the department of obstetrics with antenatally detected cystic hygroma or increased nuchal thickness on level II ultrasonography suggestive of lymphangiomas were registered in the Pediatric Surgery outpatient department. Amniocentesis, fetal ECHO and fetal MRI (if indicated)were done. Prognosis was explained to the family and mode of delivery was planned as per the obstetric indications. Postnatal evaluation included general physical examination along with ultra sound (USG)doppler of the lesion. The neonates were admitted in neonatal surgical ICU for the administration of intralesional bleomycin in a dose of 0.3 IU/kg under strict observation. All the babies were followed up at 3, 6 and 12 months. Results were segregated as excellent, good and still in follow up cohort as per the final outcome. The fetal neck masses detected antenatally and the age at first dose of bleomycin were compared with the number of sclerotherapy doses required to achieve good response.

RESULTS

Only nine patients out of 626 registered pregnancies (1.4%) were diagnosed with cystic hygroma. One antenatal mother opted for termination of pregnancy at 19 weeks of gestation and another patient was lost to follow up after receiving two doses of bleomycin in postnatal period. Maternal hypothyroidism was noted in two pregnancies. Antenatal USG shows increased nuchal thickness in 2 cases (first trimester) and 6 cases in level II scan. Amniocentesis shows normal fetal karyotyping in all these pregnancies. Fetal ECHO suggests normal biventricular function in 100% cases while fetal MRI done in one case completely ruled out any aerodigestive compromise. Mode of delivery is found to be planned elective LSCS in 57% of cases while normal vaginal delivery attained in 43% of cases as per the obstetric guidelines. Six cases achieved good response with >50% reduction in size out of which 4 cases received the dose at the first 10 days of life. Complete disappearance of lesion at the end of 6 months of follow up were seen in two babies.

CONCLUSIONS

Antenatal screening for early detection of fetal cystic hygroma with possible associated congenital aneuploidies helps in prognostication and planning the mode of delivery. A multimodality approach during intra and postpartum increases safety margin. Even huge neck masses without associated anomalies carry fair prognosis. Intralesional bleomycin is safe and prevents surgical morbidity.

Cystic Hygroma: A Preliminary Genetic Study and a Short Review from the Literature

BACKGROUND

The objective of this study is to examine the hypothesis that cystic hygroma (CH) with normal karyotype can manifest as a Mendelian inherited trait, and that a genetic similitude with hereditary lymphedema exists. To reach this goal, we investigated the prevalence of genetic variants in angiogenesis and lymphangiogenesis genes in a cohort of euploid fetuses with CH that almost resolved before delivery. A short review of cases from literature is also reported.

METHODS AND RESULTS

Five fetuses were screened using a next-generation sequencing approach by targeting 33 genes known to be associated with vascular and lymphatic malformations. The genetic evaluation revealed two novel variants in KDR and KRIT1 genes.

CONCLUSION

A review of the literature to date revealed that an association exists between CH and hereditary lymphedema and, similar to lymphedema, CH can be inherited in autosomal recessive and autosomal dominant manner, with the latter most likely associated with a better prognosis. About KDR and KRIT1 genes, no other similar associations are reported in the literature and caution is needed in their interpretation. In conclusion, we thought that a genetic test for the outcome of familial CH could be of enormous prognostic value.

Analysis of cystic hygroma diagnosed in the prenatal period: 5-years' experience at a tertiary hospital in Southeastern Turkey

PURPOSE

Our aim was to evaluate the association of cystic hygroma (CH) with fetal malformations and also to investigate the outcome of fetuses with CH diagnosed in the prenatal period.

METHODS

We divided the CH patients into two main groups as isolated CH or CH associated with the congenital structural abnormality (CSA) by measuring the thickness of CH and showing other fetal abnormalities. Pregnancy outcomes were recorded as spontaneous abortion, elective termination, intrauterine death, live birth, postnatal death, and lost to follow-up.

RESULTS

There were 74 cases of fetal CH including 19 in CSA-CH group and 55 in isolated-CH group diagnosed between 11 and 21 weeks' gestation. Karyotype analysis of these 28 patients revealed 18 (64.2%) normal karyotypes. Pregnancy outcomes included 54 elective terminations, five postnatal deaths, one spontaneous abortion, six live births, four intrauterine deaths, and four patients were lost to follow-up.

CONCLUSION

In the presence of any CSA concurrent with CH, prognosis may be considered as poor and any additional help of fetal karyotyping is questionable. But fetal karyotyping may be advocated in counseling patients with isolated CH, in which a better prognosis and resolvement of CH may be expected in case of a normal karyotype.

Prenatal Ultrasound Evaluation and Outcome of Pregnancy with Fetal Cystic Hygromas and Lymphangiomas

Cystic hygroma is a type of lymphangioma, which is a vascular anomaly associated with lymphatic malformations and formed by fluid accumulation mainly located at the cervi-cofacial and axillary regions. Cystic hygroma is mostly located in the neck (75%), followed by axilla (20%), retroperitoneum and intra-abdominal organs (2%), limbs and bones (2%), and mediastinum (1%). It is often associated with chromosome aneuploidies, hydrops fetalis, and even intrauterine fetal demise. The prognostic factors of the fetal cystic hygroma or lymphan-gioma are chromosome abnormalities, hydrops fetalis, septations, or thickness of the cystic hygroma and are associated with other major malformations. Prenatal managements including ultrasound serial follow-up, magnetic resonance imaging, or even intrauterine injection of sclerosing agents are suggested. For fetus with the risk of airway obstruction at delivery, ex utero intrapartum treatment is also indicated. Detailed prenatal counseling is necessary for better neonatal outcome.

Prenatal management, pregnancy and pediatric outcomes in fetuses with septated cystic hygroma

It has been reported that, compared with simple increased nuchal translucency, fetal cases with septated cystic hygroma (CH) are more likely to face perinatal handicaps. However, pediatric outcomes and proper prenatal counseling for this anomaly have not yet been truly defined. We performed this study to determine pregnancy and pediatric outcomes of fetuses with septated CH. We searched records for cases with septated CH and collected data for structural abnormalities, karyotype analysis, and pregnancy outcomes. Fetuses born with septated CH were also evaluated for their pediatric outcomes. Sixty-nine fetuses with septated CH were enrolled in the study. Results showed that chromosomal abnormalities were present in 28 fetuses (40.6%), and the most common aneuploidy was Turner syndrome (n=14, 20.3%); 16 (23.2%) of the remaining cases, in which aneuploidy was not found, had coexistent structural malformations; 25 (36.2%) cases had normal karyotype and morphology. The total number of live births and infants with unfavorable neurologic follow-up were 13 (18.8%) and 2 (2.9%), respectively. Septated CH is associated with poor perinatal outcomes; therefore, karyotype analysis and ultrasonographic anomaly screening should be performed as initial steps, and expectant management should be offered to couples with euploid fetuses that have normal morphology.

Analysis of the impact of PAPP-A, free β-hCG and nuchal translucency thickness on the advanced first trimester screening

OBJECTIVES

The intention of this study is to analyze the impact of the single parameters NT, PAPP-A and free β-hCG used in combined first trimester screening and to determine their contribution in the risk assessment.

METHODS

A retrospective risk assessment on the advanced first trimester screening (AFS) algorithm was made to determine the effect of a particular parameter while the remaining ones were fixed for calculation. Afterward data were recalculated by the AFS module. Test performance was measured by receiver operating characteristics (ROC) curves and their area under curve (AUC).

RESULTS

Among the 14,862 cases are 14,748 healthy fetuses, 86 with trisomy 21, 22 with trisomy 18 and 6 with trisomy 13. Some settings obtain at default cut-off a very high sensitivity. However, a lack of specificity, as a high false-positive rate, too. The ROC analysis was best for NT, followed by PAPP-A. Free β-hCG showed the lowest AUC. Combining PAPP-A and free β-hCG offered a better AUC than each parameter alone. Best test performance was obtained by including all three parameters.

DISCUSSION

A detection rate of 69 % for testing NT discretely is in order with present study data. PAPP-A is following and free β-hCG is not useful with a test positive rate of about a third. The detection rate of the biochemical parameters combined is higher than for NT alone, but results in a five times higher punctuation rate. All parameters together in the AFS provide the best test performance. The impact of each parameter NT, PAPP-A and free-β-hCG in a combined test strategy is nearly a third. Thus, every single parameter is needed to provide a high detection rate for all of the trisomies and minimize the number of unnecessary invasive diagnostics.

Increased nuchal translucency, normal karyotype and infant development

OBJECTIVE

To investigate whether chromosomally normal fetuses with a nuchal translucency (NT) ≥ 99th percentile(3.5 mm) in the first trimester have an increased risk of delayed development at 2 years of age.

METHODS

The study included children of women from 10 Danish hospitals who had fetal NT either ≥ 99th percentile (Group 1) or <95th percentile (Group 2) in the first trimester. The groups were matched by gender,gestational age at birth and maternal age. There were twice as many children in Group 2 as in Group 1. Follow-up was conducted at 2 years of age, infant development being assessed by the 'Ages and Stages Questionnaire'. The cutoff value for delayed development was defined as the 5th percentile from the first 100 questionnaires from Group 2.

RESULTS

In a 1-year period 202 of 33 266 fetuses (0.6%)had NT ≥ 3.5 mm. Of these, 99 (49.0%) were liveborn with normal karyotype and normal ultrasound findings during pregnancy. The response rate to the ASQ was 83.3% in Group 1 and 71.4% in Group 2. A low ASQ score was found in 1.3% (1/80) and 4.4% (6/137)in Groups 1 and 2, respectively (P = 0.265), but no difference was found in the mean ASQ score between the two groups (P = 0.160).

CONCLUSION

Fetuses with NT ≥ 99th percentile, normal karyotype and normal ultrasound findings during pregnancy had no increased risk of developmental delay at 2 years of age compared with fetuses with normal NT(<95th percentile).

Adverse pregnancy outcomes after abnormal first-trimester screening for aneuploidy

Women with abnormal results of first trimester screening but with a normal karyotype are at risk for adverse pregnancy outcomes. A nuchal translucency of greater than 3.5 mm is associated with an increased risk of subsequent pregnancy loss, fetal infection, fetal heart abnormalities, and other structural abnormalities. Abnormal levels of first trimester analytes are also associated with adverse pregnancy outcomes, but the predictive value is less impressive. As a single marker, pregnancy-associated plasma protein (PAPP)-A level less than 1st percentile has a good predictive value for subsequent fetal growth restriction. Women with PAPP-A level less than 5th percentile should undergo subsequent risk assessment with routine maternal serum afetoprotein screening with the possible addition of uterine artery pulsatility index assessment in the midtrimester.

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.

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.

Estudo da translucência nucal, ducto venoso, osso nasal e idade materna na detecção de cromossomopatia fetal em uma população de alto risco

OBJETIVO: Avaliar a translucência nucal, o ducto venoso, o osso nasal e a idade materna > 35 anos como testes de rastreamento para aneuploidias entre 12 e 14 semanas de gestação em pacientes de alto risco. MATERIAIS E MÉTODOS: Estudo prospectivo observacional envolvendo 92 gestantes entre 12 e 14 semanas submetidas a biópsia de vilo corial por alto risco de trissomia, baseado na medida da translucência nucal (17,4%) e idade materna >35 anos (78,3%). Antes da biópsia de vilo corial, realizaram-se medida da translucência nucal, avaliação de fluxo no ducto venoso e identificação do osso nasal. Calcularam-se a sensibilidade, a especificidade, o valor preditivo positivo e o valor preditivo negativo para testes realizados em paralelo e em seqüência. RESULTADOS: Encontrou-se alteração cromossômica em 12 (13,5%) fetos; 7 (58,3%) apresentavam trissomia 21. Osso nasal foi identificado em todos os fetos com trissomia. Translucência nucal, ducto venoso e idade materna isolados mostraram baixa sensibilidade (41,67-58,33%) e baixo valor preditivo positivo (10-45,45%). A associação translucência nucal + ducto venoso + idade materna apresentou o melhor resultado (sensibilidade: 100%; especificidade: 6,49%; valor preditivo positivo: 14,29%; valor preditivo negayivo: 100%). CONCLUSÃO: Em gestantes com idade > 35 anos, a associação translucência nucal + ducto venoso mostra-se como a mais sensível para a indicação de procedimento invasivo.

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.

Clinical first-trimester routine screening for Down syndrome in singleton pregnancies in northern Finland

OBJECTIVE

The purpose of this study was to compare the efficacy of both separate and combined maternal serum testing and fetal nuchal translucency measurement in the first trimester screening for Down syndrome in northern Finland.

STUDY DESIGN

The following screening tests were evaluated: measurement of nuchal translucency (NT) alone; serum screening (pregnancy-associated plasma protein A [PAPP-A] and free beta subunit of human chorionic gonadotropin [beta-hCG]) alone; and combined screening (NT plus PAPP-A and free beta-hCG).

RESULTS

The participants comprised 7534 pregnant women during the 10+0-12+6 weeks of pregnancy. All 7534 women participated in serum screening, and 4765 women participated in combined screening. In the serum screening-alone group, there were 30 cases of trisomy 21, of which 23 (76%) were detected. In the combined-screening group, there were 24 cases of trisomy 21 and 21 (87.5%) were detected. In the combined-screening group NT alone detected 15 cases of Down syndrome (62%).

CONCLUSION

Combined screening is the method of choice for Down syndrome screening.

[Increased nuchal translucency and cystic hygroma in the first trimester: prenatal diagnosis and neonatal outcome]

OBJECTIVE

A prospective study of pregnancy outcome in fetuses with increased nuchal translucency above the 95th centile (group NT) or cystic hygroma (group CH) at 10 to 14 weeks of gestation was performed.

PATIENTS AND METHODS

Maternal and fetal data (nuchal translucency, caryotype, pregnancy outcome) and infant follow-up of 223 fetuses with first trimester nuchal translucency thickness (183 NT and 40 CH) were analysed.

RESULTS

The measurement of nuchal translucency thickness shows a significant difference between group CH and NT (7.4+/-2.9 mm compared 3.7+/-0.8 mm). Chromosomal abnormalities were present in 55% (22/40) in group CH, with 9 cases/22 (40.9%) of Turner syndrome, compared with 14.2% (26/183) in group NT with trisomy 21 in 15 cases/26 (57.7%) (P<0.05). The rate of unfavourable outcome of pregnancy (spontaneous abortion, elective termination of pregnancy, serious structural anomalies) was 80% (32/40) in group CH compared with 18% (33/183) in group NT (P<0.05). In chromosomally normal pregnancies, the rate of fetus with no visible serious structural anomalies was 44.4% (8/18) in group CH compared with 93% (146/157) in group NT (P<0.05).

DISCUSSION AND CONCLUSION

Our data show ultrasonographic evaluation of the fetal nuchal translucency thickness at the first trimester is actually indispensable. Neonatal outcome and malformation rate in fetuses with increased nuchal translucency or cystic hygroma are different, even with normal karyotype.

[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.

Karyotype and outcome of fetuses diagnosed with cystic hygroma in the first trimester in relation to nuchal translucency thickness

OBJECTIVES

To determine the incidence and to examine the karyotype and the outcome of fetuses diagnosed with cystic hygroma (CH) at 11-14 weeks of gestation.

METHODS

The presence of bilateral cystic anechoic cavities in the neck, nuchal translucency (NT), malformations and hydrops was prospectively recorded in 6894 ultrasound examinations in the first trimester, between 2001 and 2004.

RESULTS

Forty-two fetuses (0.62%) were diagnosed with CH in the first trimester of pregnancy and 60% of these had an abnormal karyotype. NT was > or = 3 mm in 83% and hydrops was present in 40% of the cases. The karyotype was abnormal in 25 (69%) of these, showing trisomy 18 and 45,XO more often than trisomy 21. NT was <3 mm in seven cases (17%); no hydrops was present and only one had an abnormal karyotype (47 + 18). Eight babies with CH without aneuploidy or hydrops were born alive, seven among them were without malformations and are developing normally at 1 to 18 months of age, the remaining one presented with CHARGE syndrome.

CONCLUSIONS

CH is an independent entity from NT and its association with increased NT carries a poor prognosis.

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.

Increased nuchal translucency and distended jugular lymphatic sacs on first-trimester ultrasound

OBJECTIVE

To investigate the presence and volume of jugular lymphatic sacs (JLS) in first-trimester fetuses with normal nuchal translucency thickness (NT) and in those with increased NT.

METHODS

This was a prospective study of 26 fetuses with NT > 95(th) percentile, which were compared with 137 fetuses with normal NT. Following crown-rump length (CRL) and NT measurement the neck region of the fetus was studied by transvaginal ultrasound. The JLS presented as spheroidal translusencies in the anterolateral region of the neck.

RESULTS

The prevalence of JLS differed significantly between fetuses with enlarged NT and the control group (P < 0.0001). In the group of 26 fetuses with increased NT, 22 had clearly visible JLS. Chorionic villus sampling revealed aneuploidy in 10 and euploidy in 16 fetuses. In the control group two fetuses, with NT values of 2.8 mm and 2.9 mm, had JLS; pregnancy outcome was normal in both cases. Logistic regression analysis in the total study group showed that an increase in NT was associated with a greater probability of JLS being present (for NT = 3-3.5 mm, probability = 0.67; for NT > 3.5 mm, probability = 0.93). In fetuses with JLS, an increase in CRL was associated with a significant increase in right JLS volume (r = 0.51; P-value = 0.01) and a non-significant increase in left sac volume (r = 0.40; P-value = 0.09). Increase in NT was not associated with a significant increase in JLS volume.

CONCLUSION

There is a significant association between increased NT and the presence of JLS on first-trimester ultrasound. In our opinion, the pathophysiological explanation for increased NT lies in a disturbance in lymphangiogenesis.

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 distribution of fetal nuchal translucency thickness in normal Korean fetuses

The aim of present study was to establish normative data for the distribution of nuchal translucency (NT) thickness in normal Korean fetuses. The data were collected from pregnant women with singleton pregnancies in whom fetal ultrasound was performed and the fetal NT thickness was measured between 11 and 14 weeks of gestation. Among them, a total of 2,577 fetuses with a known normal outcome were included in this study. The distribution of multiple of median (MoM) values of the NT thickness with crown-rump length (CRL) in 10-mm intervals and the 95th percentile of MoM were calculated with the linear regression method. The present study showed that NT measurements increase with increasing CRL and a false positive rate increases with increasing gestational age. Therefore, a fixed cut-off point through the first trimester was not appropriate and each NT measurement should be examined according to the gestational age. The present study offers normative data of the fetal NT thickness in a Korean population, which can be used as reference for screening chromosomal aberrations or other congenital abnormalities in the first trimester.

Outcome of pregnancy in chromosomally normal fetuses with increased nuchal translucency in the first trimester

OBJECTIVES

To study the outcome of chromosomally normal pregnancies with increased nuchal translucency at the 10-14-week scan.

DESIGN

Retrospective study of 1320 chromosomally normal singleton pregnancies with nuchal translucency of > or = 3.5 mm. In addition to fetal karyotyping these patients were managed with follow-up scans at 14-16 and 20-22 weeks, specialist fetal echocardiography and in selected cases by infection screening and further genetic testing.

RESULTS

In the 1320 pregnancies there were 68 (5.15%) spontaneous abortions or intrauterine deaths, 18 (1.36%) neonatal and infant deaths and 154 (11.67%) terminations of pregnancy. In the 1080 (81.82%) survivors, 60 (5.56%) had abnormalities requiring medical or surgical treatment or leading to mental handicap. The chance of a livebirth with no defects in the group with nuchal translucency of 3.5-4.4 mm was 86%, for those with translucency of 4.5-5.4 mm it was 77%, for those with translucency of 5.5-6.4 mm it was 67%, and for those with translucency of > or = 6.5 mm it was 31%.

CONCLUSIONS

Increased fetal nuchal translucency is associated with chromosomal abnormalities, many fetal defects and genetic syndromes. In the majority of cases a series of antenatal investigations, including fetal karyotyping, detailed scans, fetal echocardiography, as well as genetic testing and infection screening, that can be completed by 20 weeks of gestation would distinguish between the pregnancies destined to result in adverse outcome and those leading to the delivery of infants without major defects.

First-trimester ultrasound

There has been an increase in the use of fetal ultrasound in the first trimester. This article reviews the published literature with emphasis on fetal nuchal translucency (NT). When measured according to well-defined guidelines, increased NT identifies about 80% of chromosomal anomalies for a false-positive rate of about 5%. Increased NT may indicate the presence of structural defects or genetic disorders, and it is relatively frequently seen in monochorionic pregnancies prone to develop twin-twin transfusion syndrome.

Evaluation of first trimester maternal serum and ultrasound screening for Down's syndrome in Eastern and Northern Finland

The current trend in prenatal diagnosis is that trisomy screening is being moved to the first trimester and ultrasonographic nuchal translucency measurement is included in risk calculation. It is likely that biochemical screening in the second trimester will gradually be given up. In Eastern and Northern Finland, during the year 1999 we offered first-trimester ultrasonographic and serum screening for trisomy 21, with measurements of maternal serum PAPP-A and beta-hCG. A total of 2515 pregnant women participated in the screening, yielding the detection of eight foetuses with Down's syndrome. Six affected foetuses (75%) were detected by means of first-trimester serum screening. Since we were in the phase of collecting data for the Finnish medians for PAPP-A and beta-hCG, the women were not given the estimates of risk for trisomy 21. Only 1602 of the 2515 enrolled women had the combination of first-trimester ultrasonographic and serum screening performed, and in that group there were five foetuses with Down's syndrome. The combination ultrasonographic and serum approach yielded a Down's syndrome detection rate of 80% (four out of five) with a 5% false positive rate, whereas in nuchal translucency based-screening the detection rate was 60%, with a 5% false positive rate.

The role of ductus venosus blood flow assessment in screening for chromosomal abnormalities at 10-16 weeks of gestation

OBJECTIVE

To evaluate the role of ductus venosus blood flow assessment at 10-16 weeks' gestation in screening for chromosomal abnormalities.

METHODS

Ductus venosus blood flow was prospectively evaluated in 1371 consecutive pregnancies between 10 and 16 weeks of gestation. The pulsatility index for veins was calculated. All cases were screened for chromosomal defects combining maternal age and fetal nuchal translucency thickness.

RESULTS

A chromosomal abnormality was found in 20 cases. The overall detection rate, specificity, positive predictive value, negative predictive value and odds ratio for chromosomal abnormalities were 65%, 95.7%, 18.3%, 99.5% and 41 (95% CI 16-108), respectively, when using the 95th centile pulsatility index as a cut-off.

CONCLUSIONS

These preliminary results suggest that evaluation of the ductus venosus pulsatility index at 10-16 weeks' gestation is a useful second-line screening test for chromosomal defects. A combination of nuchal translucency measurement and ductus venosus assessment might increase specificity while maintaining an optimal detection rate for chromosomal abnormalities. Such a policy could identify 55% of all chromosomal abnormalities and about 69% of autosomal trisomies, reducing the need for invasive testing to less than 1%.

Nuchal translucency and its relationship to congenital heart disease

Nuchal translucency refers to the normal subcutaneous space, observed on first trimester ultrasound evaluation, between the skin and cervical spine. Increased nuchal translucency is known to be associated with an increased risk of aneuploidy, particularly Trisomy 21, and recent studies have also identified increased nuchal translucency as a nonspecific marker for various genetic syndromes and multiple structural anomalies, to include congenital heart disease. This increased risk applies to euploid and aneuploid pregnancies and is directly related to the degree of nuchal translucency thickening. This article reviews the role of nuchal translucency as a screening tool for congenital heart disease.

First trimester screening for structural fetal abnormalities: nuchal translucency sonography

Nuchal translucency refers to the normal subcutaneous space, observed on first trimester ultrasound examination, between the skin and the cervical spine in the fetus. Increased nuchal translucency is known to be associated with an increased risk of aneuploidy, particularly Down syndrome. In addition to this association with aneuploidy, multiple studies have now identified increased nuchal translucency as a nonspecific marker of a wide range of fetal structural abnormalities, to include congenital diaphragmatic hernia, cardiac defects, and various genetic syndromes. The degree of nuchal translucency is directly related to the prevalence of fetal anomalies and may have prognostic significance, especially when found in association with other anomalies. The pathophysiology of increased nuchal translucency is uncertain but may be the result of cardiac failure or alterations in lymphatic drainage. Increased nuchal translucency may identify pregnancies that require further assessment, to include additional sonographic evaluation and possible fetal echocardiography. Further evaluation is required to assess the role of nuchal translucency screening in the general population.

First trimester screening for aneuploidy: nuchal translucency sonography

Prenatal diagnosis of fetal aneuploidy is a continuously and rapidly evolving area of research. Currently in the United States, the standard of care for screening pregnancies for aneuploidy involves assessment of maternal age together with the use of multiple second trimester maternal serum markers. This screening approach identifies approximately 60% of pregnancies with fetuses affected with Down syndrome and provides results in the second trimester of pregnancy. First trimester screening for aneuploidy by using nuchal translucency sonography is one of the most promising areas of research in the detection of Down syndrome. This screening method involves measuring the normal space located between the cervical spine and overlying fetal skin at 10 to 14 weeks' gestation. Studies from both high risk and unselected patient populations suggest significant advantages to this approach for Down syndrome detection compared with currently available second trimester screening methods. The combination of first trimester biochemical screening and nuchal translucency measurements may further improve the efficacy of prenatal screening for aneuploidy. The article reviews studies suggesting a role for nuchal-translucency-based aneuploidy screening and describes areas of ongoing research in this field.

The value of sonography in early pregnancy for the detection of fetal abnormalities in an unselected population

OBJECTIVE

To determine the value of early pregnancy sonography in detecting fetal abnormalities in an unselected obstetric population. DESIGN Prospective cross-sectional study. All women initially underwent transabdominal sonography and when the anatomical survey was considered to be incomplete, transvaginal sonography was also performed (20.1%). Nuchal translucency was measured and karyotyping was performed as appropriate.

SETTING

University Department of Obstetrics and Gynaecology.

PARTICIPANTS

6634 sequential unselected women (mean maternal age 29.9 years, range 13-50; mean gestational age 12+4 weeks, range 11+0-14+6), carrying 6443 live fetuses participated in this study.

MAIN OUTCOME MEASURE

Detection rate of fetal anomalies and the associated cost per case detected in early pregnancy.

RESULTS

The incidence of anomalous fetuses was 1.4% (92/6443) including 43 chromosomal abnormalities. The detection rate for structural abnormalities was 59.0% (37/63, 95% CI 46.5-72.4) and the specificity was 99.9% in early pregnancy. When the first and second trimester scans were combined, the detection for structural abnormalities was 81.0% (51/63, 95% CI 67.7-89.2). Seventy-eight percent (31/40) of chromosomal abnormalities (excluding three cases of XXY) were diagnosed at 11-14 weeks, either because of a nuchal translucency greater than or equal to the 99th centile for gestational age (43%; 17/40, 95% CI 27.4-60.4), or due to the presence of structural abnormalities (35%; 14/40, 95% CI 21.2-52.8). Sixty-five percent (15/23) of cases of trisomy 21 were also diagnosed either because of having a nuchal translucency greater than or equal to the 99th centile (57.0%; 13/23) or due to the presence of a structural abnormality (9.0%; 2/23). Overall, the detection rate of structurally abnormal fetuses was 59% (37/63) in early pregnancy and 81% in combination with the second trimester scan. The cost per abnormality diagnosed in early pregnancy is estimated to be pound sterling 6258 per structurally abnormal fetus, pound sterling 7470 per chromosomal abnormality and pound sterling 4453 per anomalous fetus.

CONCLUSION

The majority of fetal structural and chromosomal abnormalities can be detected by sonographic screening at 11-14 weeks, but the second trimester scan should not be abandoned.

Can nuchal cord cause transient increased nuchal translucency thickness?

When detected in a first trimester scan, an increased thickness of nuchal translucency (NT) may be associated with chromosomal, cardiac or genetic disorders. However, less attention has been devoted to the outcome of those fetuses who have confirmed normal anatomies and karyotyping, but have abnormal first trimester scans. Thus, a challenging new issue is how to counsel such cases of transient increased NT in which the translucency rapidly vanishes with no evidence of other underlying abnormalities. Two cases of transient increased thickness of NT are reported. In both, a nuchal cord was ultrasonographically demonstrated and a thorough work-up revealed chromosomally and anatomically normal fetuses. The pathophysiological theories behind these observations and their significance are discussed. Based on these observations, we suggest that transvaginal sonography combined with Doppler flow studies should be utilized for the presize detection of cord patterns to accomplish the work-up in cases of increased NT.

UK multicentre project on assessment of risk of trisomy 21 by maternal age and fetal nuchal-translucency thickness at 10-14 weeks of gestation. Fetal Medicine Foundation First Trimester Screening Group

BACKGROUND

Prenatal diagnosis of trisomy 21 currently relies on assessment of risk followed by invasive testing in the 5% of pregnancies at the highest estimated risk. Selection of the high-risk group by a combination of maternal age and second-trimester maternal serum biochemistry gives a detection rate of about 60%. We investigated assessment of risk by a combination of maternal age and fetal nuchal-translucency thickness, measured by ultrasonography at 10-14 weeks of gestation.

METHODS

The risk of trisomy 21 was estimated for 96127 women of median age 31 years (range 14-49) with singleton pregnancies. Ultrasonography was done by 306 appropriately trained sonographers in 22 centres. Risk of trisomy 21 was calculated from the maternal age and gestational-age-related prevalence, multiplied by a likelihood ratio depending on the deviation from normal in nuchal-translucency thickness for crown-rump length. The distribution of risks was investigated and the sensitivity of a cut-off risk of 1 in 300 was calculated. Phenotype was assessed by fetal karyotyping or clinical examination of liveborn infants.

FINDINGS

The estimated trisomy-21 risk, from maternal age and fetal nuchal-translucency thickness, was 1 in 300 or higher in 7907 (8.3%) of 95476 normal pregnancies, 268 (82-2%) of 326 with trisomy 21, and 253 (77.9%) of 325 with other chromosomal defects. The 5% of the study population with the highest estimated risk included 77% of trisomy-21 cases.

INTERPRETATION

Selection of the high-risk group for invasive testing by this method allows the detection of about 80% of affected pregnancies. However, even this method of risk assessment requires about 30 invasive tests for identification of one affected fetus.

Antenatal screening for Down's syndrome

BACKGROUND

In 1968 the first antenatal diagnosis of Down's syndrome was made and screening on the basis of selecting women of advanced maternal age for amniocentesis was gradually introduced into medical practice. In 1983 it was shown that low maternal serum alpha fetoprotein (AFP) was associated with Down's syndrome. Later, raised maternal serum human chorionic gonadotrophin (hCG), and low unconjugated oestriol (uE3) were found to be markers of Down's syndrome. In 1988 the three biochemical markers were used together with maternal age as a method of screening, and this has been widely adopted. PRINCIPLES OF ANTENATAL SCREENING FOR DOWN'S SYNDROME: Methods of screening need to be fully evaluated before being introduced into routine clinical practice. This included choosing markers for which there is sufficient scientific evidence of efficacy, quantifying performance in terms of detection and false positive rates, and establishing methods of monitoring performance. Screening needs to be provided as an integrated service, coordinating and managing the separate aspects of the screening process. SERUM MARKERS AT 15-22 WEEKS OF PREGNANCY: A large number of serum markers have been found to be associated with Down's syndrome between 15 and 22 weeks of pregnancy. The principal markers are AFP, hCG or its individual subunits (free alpha- and free beta-hCG), uE3, and inhibin A. Screening performance varies according to the choice of markers used and whether ultrasound is used to estimate gestational age (table 1). When an ultrasound scan is used to estimate gestational age the detection rate for a 5% false positive rate is estimated to be 59% using the double test (AFP and hCG), 69% using the triple test (AFP, hCG, uE3), and 76% using the quadruple test (AFP, hCG, uE3, inhibin A), all in combination with maternal age. Other factors that can usefully be taken into account in screening are maternal weight, the presence of insulin dependent diabetes mellitus, multiple pregnancy, ethnic origin, previous Down's syndrome pregnancy, and whether the test is the first one in a pregnancy or a repeat. Factors such as parity and smoking are associated with one or more of the serum markers, but the effect is too small to justify adjusting for these factors in interpreting a screening test.

URINARY MARKERS AND FETAL CELLS IN MATERNAL BLOOD

Urinary beta-core hCG has been investigated in a number of studies and shown to be raised in pregnancies with Down's syndrome. This area is currently the subject of active research and the use of urine in future screening programmes may be a practical possibility. Other urinary markers, such as total oestriol and free beta-hCG may also be of value. Fetal cells can be identified in the maternal circulation and techniques such as fluorescent in situ hybridisation can be used to identify aneuploidies, including Down's syndrome and trisomy 18. This approach may, in the future, be of value in screening or diagnosis. Currently, the techniques available do not have the performance, simplicity, or economy needed to replace existing methods.

DEMONSTRATION PROJECTS

Demonstration projects are valuable in determining the feasibility of screening and in refining the practical application of screening. They are of less value in determining the performance of different screening methods. Several demonstration projects have been conducted using the triple and double tests. In general, the uptake of screening was about 80%. The screen positive rates were about 5-6%. About 80% of women with positive screening results had an invasive diagnostic test, and of those found to have a pregnancy with Down's syndrome, about 90% chose to have a termination of pregnancy. ULTRASOUND MARKERS AT 15-22 WEEKS OF PREGNANCY: There are a number of ultrasound markers of Down's syndrome at 15-22 weeks, including nuchal fold thickness, cardiac abnormalities, duodenal atresia, femur length, humerus length, pyelectasis, and hyperechogenic bowel. (ABSTRA

Outcome of chromosomally normal livebirths with increased fetal nuchal translucency at 10-14 weeks' gestation

The aim of this study was to determine the outcome of chromosomally normal livebirths with increased fetal nuchal translucency at 10-14 weeks' gestation. Clinical follow up of 89 chromosomally normal livebirths that in fetal life had a minimum nuchal translucency thickness of 3.5 mm and a comparison group of 302 infants whose fetal nuchal translucency thickness at 10-14 weeks of gestation was less than 3.5 mm was performed. Major abnormalities, mainly structural defects of the cardiovascular or skeletal systems, were found in 10.1% (nine of 89) of the group with increased translucency, compared to 2% (five of 302) in those with translucency of less than 3.5 mm (chi2=11.9, p<0.001). Delay in achievement of developmental milestones was observed in one of the infants with increased translucency and in one of the comparison group. The findings of this study show that in chromosomally normal fetuses increased nuchal translucency thickness at 10-14 weeks of gestation is a marker for fetal abnormalities including structural defects and genetic syndromes.

First trimester sonographic detection of chromosomal abnormalities in an unselected population

OBJECTIVE

To investigate the role of first trimester sonography in detecting chromosomal abnormalities in an unselected obstetric population.

METHODS

2281 women (mean maternal age 30 years [range 16-47]; mean gestational age 12(+3) weeks [range 11-14]) underwent transabdominal scanning to assess fetal structure and, if anatomical survey was considered to be incomplete (31% of cases), transvaginal sonography was also performed. Measurement of nuchal translucency was included and karyotyping performed as considered appropriate.

RESULTS

There were 16 chromosomal abnormalities; 13 (81%) were diagnosed at 11-14 weeks either because of a nuchal translucency greater than or equal to the 99th centile for gestational age (7/16; 44% [95% CI 25-63]) or due to the presence of structural abnormalities (6/16; 38% [95% CI 14.2-61.8]). Seventy-five percent of cases of trisomy 21 were also diagnosed either because of having a nuchal translucency greater than or equal to the 99th centile (5/8; 63%) or due to the presence of a structural abnormality (1/8; 13%).

CONCLUSIONS

A significant proportion of fetal chromosomal abnormalities can be detected by first trimester sonographic screening to assess fetal structural appearance. The sensitivity of detection can be improved by combining measurement of nuchal translucency with detailed examination of fetal anatomy.

Noninvasive first-trimester screening for fetal aneuploidy

We reviewed all studies concerning noninvasive first trimester screening for fetal aneuploidy obtained from a MEDLINE search through June 1996 with additional sources identified through cross-referencing. Three screening and diagnostic modalities are of potential application in noninvasive first trimester testing for fetal aneuploidy: ultrasound, maternal biochemical markers, and analysis of fetal cells retrieved from maternal sources. Sensitivities of the sonographic finding of nuchal translucency thickness in combination with maternal age for trisomy 21, performed between 10 and 14 weeks of gestation in experienced hands, and maternal biochemical markers independently may be as high as 86 percent and 60 percent, respectively. Sensitivity, specificity, and predictive values of these diagnostic modalities alone, in combination with each other, or in conjunction with other predisposing factors such as maternal age, in large low risk populations have not currently been established. Analysis of fetal cells retrieved from maternal sources, although more complex, may offer definitive noninvasive prenatal diagnosis yet is not currently available in clinical practice. We conclude that noninvasive first trimester screening for fetal aneuploidy modalities including sonographic examination for nuchal translucency thickness and maternal biochemical markers, is feasible. Clinical feasibility; and all-encompassing clinical management paradigms of these and other early noninvasive first trimester screening methods for fetal aneuploidy, are not yet available.