Aberrant right subclavian artery: embryology, prenatal diagnosis and clinical significance.

Introduction: The right subclavian artery normally arises as the first vessel from the brachiocephalic trunk. An aberrant right subclavian artery (ARSA) arises directly from the aortic arch and crosses behind the trachea towards the right arm. This variant occurs in approximately 1-2% of the population; however, the frequency increases in individuals with chromosomal abnormalities such as trisomy 21 and 22q11.2 microdeletion. Prenatal identification of ARSA therefore has a role in screening for such conditions. Methods: Databases were searched for studies reporting the prenatal ultrasound evaluation of ARSA and its frequency in normal fetuses and in those with chromosomal abnormalities. Results: A total of 23 studies were evaluated. Feasibility for the ultrasound evaluation of ARSA was 85-95%. The sonographic detection of ARSA is best in the three-vessel trachea view; however, sagittal and coronal imaging of the aortic arch may be useful. ARSA in isolation was not found to be associated with chromosomal abnormalities. The prevalence of ARSA in chromosomally abnormal fetuses was up to 24-fold higher than in normal fetuses, but the majority of chromosomally abnormal fetuses with ARSA had additional abnormal ultrasound findings, particularly cardiac abnormalities. Conclusions: The prenatal detection of ARSA is a clinically useful prenatal marker for chromosomal abnormalities. In isolation, it is unlikely to be associated with pathogenic genetic variants. The ultrasound diagnosis of ARSA should prompt meticulous assessment of associated abnormalities. Invasive diagnostic testing should be offered to patients with non-isolated ARSA or in the presence of non-reassuring screening results or other risk factors.

Reexamining the optimal nuchal translucency cutoff for diagnostic testing in the cell-free DNA and microarray era: results from the Victorian Perinatal Record Linkage study.

BACKGROUND: The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine recently recommended offering genetic counseling and diagnostic testing for enlarged nuchal translucency at ≥3.0 mm, regardless of previous negative screening with noninvasive prenatal testing. OBJECTIVE: This study aimed to perform a population-based, individual record linkage study to determine the optimal definition of an enlarged nuchal translucency for the detection of atypical chromosome abnormalities. STUDY DESIGN: This was a retrospective study of women resident in Victoria, Australia, undergoing combined first-trimester screening during the 24-month period from January 2015 to December 2016. Linkages between statewide results for combined first-trimester screening, prenatal diagnostic procedures, and postnatal cytogenetic results from products of conception and infants up to 12 months of age were used to ascertain the frequency and type of chromosome abnormality by gestation and nuchal translucency measurement. An atypical chromosome abnormality was defined as any major chromosome abnormality other than whole chromosome aneuploidy involving chromosomes 21, 18, 13, X, and Y. RESULTS: Of the 81,244 singleton pregnancies undergoing combined first-trimester screening, 491 (0.60%) had a nuchal translucency of ≥3.5 mm, 534 (0.66%) had a nuchal translucency of 3.0 to 3.4 mm, and 80,219 (98.74%) had a nuchal translucency of < 3.0 mm. When grouped by nuchal translucency multiples of the median (MoM), 192 (0.24%) had a nuchal translucency of ≥3.0 MoM, 513 (0.63%) had a nuchal translucency of 1.9 to 2.9 MoM, and 80,539 (99.13%) had a nuchal translucency of <1.9 MoM. A total of 1779 pregnancies underwent prenatal or postnatal diagnostic testing, of which 89.60% were performed by whole-genome single-nucleotide polymorphism chromosomal microarray. The frequency of total major chromosome abnormalities was significantly higher in the group with a nuchal translucency of ≥3.5 mm (147 of 491, 29.94%) than the group with a nuchal translucency of 3.0 to 3.4 mm (21 of 534, 3.93%) or a nuchal translucency of <3.0 mm (71 of 80,219, 0.09%) (P<.001). There were 93 atypical chromosome abnormalities in the total screened cohort. The frequency of an atypical chromosome abnormality was 4.07% (95% confidence interval, 2.51-6.22), 0.37% (95% confidence interval, 0.05-1.35), and 0.09% (95% confidence interval, 0.07-0.11) in the groups with a nuchal translucency of ≥3.5 mm, 3.0 to 3.4 mm, and <3.0 mm, respectively. The frequency of atypical chromosome abnormalities was 4.69% (95% confidence interval, 2.17-8.71), 2.53% (95% confidence interval, 1.36-4.29), and 0.09% (95% confidence interval, 0.07-0.11) in the groups with a nuchal translucency of ≥3.0 MoM, 1.9 to 2.9 MoM, and <1.9 MoM, respectively. When defining thresholds for offering diagnosis with chromosomal microarray at 11 to 13 weeks, both a nuchal translucency threshold of 1.9 MoM and a fixed threshold of 3.0 mm captured 22 of 93 fetuses (23.7%) with an atypical chromosome abnormality. Of these, 50.0% had a coexisting fetal abnormality on ultrasound. However, the gestation-specific threshold of 1.9 MoM had a better specificity than 3.0 mm. The positive predictive value of an enlarged nuchal translucency for any atypical chromosome abnormality was 1 in 47 for nuchal translucency of >3.0 mm and 1 in 32 for nuchal translucency of >1.9 MoM. Our nuchal translucency threshold of 1.9 MoM captured 0.87% of fetuses, thus approximating the 99th centile. CONCLUSION: A gestational age-adjusted nuchal translucency threshold of 1.9 MoM or 99th centile is superior to the fixed cutoff of 3.0 mm for the identification of atypical chromosome abnormalities. The risk of an atypical chromosome abnormality in a fetus with an enlarged nuchal translucency is more than tripled in the presence of an additional ultrasound abnormality.

A minimum estimate of the prevalence of 22q11 deletion syndrome and other chromosome abnormalities in a combined prenatal and postnatal cohort.

STUDY QUESTION: What is the frequency of major chromosome abnormalities in a population-based diagnostic data set of genomic tests performed on miscarriage, fetal and infant samples in a state with >73 000 annual births? SUMMARY ANSWER: The overall frequency of major chromosome abnormalities in the entire cohort was 28.2% (2493/8826), with a significant decrease in the detection of major chromosome abnormalities with later developmental stage, from 50.9% to 21.3% to 15.6% of tests in the miscarriage, prenatal and postnatal cohorts, respectively. WHAT IS KNOWN ALREADY: Over the past decade, technological advances have revolutionized genomic testing at every stage of reproduction. Chromosomal microarrays (CMAs) are now the gold standard of chromosome assessment in prenatal diagnosis and pediatrics. STUDY DESIGN, SIZE, DURATION: A population-based cohort study including all chromosome analysis was performed in the Australian state of Victoria during a 24-month period from January 2015 to December 2016. All samples obtained via invasive prenatal diagnosis and postnatal samples from pregnancy tissue and infants ≤12 months of age were included. PARTICIPANTS/MATERIALS, SETTING, METHODS: A research collaboration of screening and diagnostic units in the Australian state of Victoria was formed (the Perinatal Record Linkage collaboration), capturing all instances of prenatal and postnatal chromosome testing performed in the state. Victoria has over 73 000 births per annum and a median maternal age of 31.5 years. We analyzed our population-based diagnostic data set for (i) chromosome assessment of miscarriage, prenatal diagnosis and postnatal samples; (ii) testing indications and diagnostic yields for each of these cohorts; (iii) and the combined prenatal/infant prevalence of 22q11.2 deletion syndrome (DS) as a proportion of all births ≥20 weeks gestation. MAIN RESULTS AND THE ROLE OF CHANCE: During the 24-month study period, a total of 8826 chromosomal analyses were performed on prenatal and postnatal specimens in Victoria. The vast majority (91.2%) of all chromosome analyses were performed with CMA.The overall frequency of major chromosome abnormalities in the entire cohort was 28.2% (2493/8826). There was a significant decreasing trend in the percentage of chromosome abnormalities with later developmental stage from 50.9% to 21.3% to 15.6% in the miscarriage, prenatal and postnatal cohorts, respectively (χ2 trend = 790.0, P < 0.0001). The total frequency of abnormalities in the live infant subgroup was 13.4% (244/1816). The frequencies of pathogenic copy number variants (CNVs) detected via CMA for the miscarriage, prenatal and postnatal cohorts were 1.9% (50/2573), 2.2% (82/3661) and 4.9% (127/2592), respectively. There was a significant increasing trend in the frequency of pathogenic CNVs with later developmental stage (χ2 trend = 39.72, P < 0.0001). For the subgroup of live infants, the pathogenic CNV frequency on CMA analysis was 6.0% (109/1816). There were 38 diagnoses of 22q11.2 DS, including 1 miscarriage, 15 prenatal and 22 postnatal cases. After excluding the miscarriage case and accounting for duplicate testing, the estimated prevalence of 22q11 DS was 1 in 4558 Victorian births. LIMITATIONS, REASONS FOR CAUTION: Clinical information was missing on 11.6% of postnatal samples, and gestational age was rarely provided on the miscarriage specimens. We were unable to obtain rates of termination of pregnancy and stillbirth in our cohort due to incomplete data provided by clinical referrers. We therefore cannot make conclusions on pregnancy or infant outcome following diagnostic testing. Childhood and adult diagnoses of 22q11 DS were not collected. WIDER IMPLICATIONS OF THE FINDINGS: Our study marks a complete transition in genomic testing from the G-banded karyotype era, with CMA now established as the first line investigation for pregnancy losses, fetal diagnosis and newborn/infant assessment in a high-income setting. Integration of prenatal and postnatal diagnostic data sets provides important opportunities for estimating the prevalence of clinically important congenital syndromes, such as 22q11 DS. STUDY FUNDING/COMPETING INTEREST(S): L.H. is funded by a National Health and Medical Research Council Early Career Fellowship (1105603); A.L. was funded by a Mercy Perinatal Research Fellowship; J.H. was funded by a National Health and Medical Research Council Senior Research Fellowship (10121252). The funding bodies had no role in the conduct of the research or the manuscript. Discretionary funding from the Murdoch Children's Research Institute has supported the prenatal diagnosis data collection and reporting over the years.Dr Ricardo Palma-Dias reports a commercial relationship with Roche Diagnostics, personal fees from Philips Ultrasound, outside the submitted work. Debbie Nisbet reports a commercial relationship with Roche Diagnostics, outside the submitted work. TRIAL REGISTRATION NUMBER: NA.

Association between timing of diagnosis of trisomy 21, 18, and 13 and maternal socio-economic status in Victoria, Australia: A population-based cohort study from 2015 to 2016.

OBJECTIVES: To explore the association between timing of diagnosis of common autosomal trisomies, maternal age, and socio-economic status (SES). DESIGN: Retrospective study of cytogenetic diagnoses of trisomy 21 (T21), trisomy 18 (T18), and trisomy 13 (T13) in Victoria, Australia, in 2015 to 2016, stratified by timing (prenatal less than 17 weeks gestation, prenatal including or greater than or 17 weeks gestation, and postnatal before 12 months of age), maternal age, and SES region. Utilisation of prenatal testing following a live-born T21 infant was ascertained via record linkage. RESULTS: Among 160 230 total births were 571 diagnoses of T21 and 246 of T18/T13. The overall and live birth prevalences of T21 were 3.56 and 0.47 per 1000 births, respectively. Compared with women from disadvantaged SES regions, women from high SES regions were more likely to have a prenatal diagnosis of a trisomy before 17 weeks than after (P < .01) and less likely to have a live-born T21 infant than a prenatal diagnosis (P < .01). There was a significant trend to higher live birth rates of T21 with lower SES (P = .004). The majority (68.5%) of women who gave birth to a live infant with T21 did not utilise prenatal testing. CONCLUSION: There is a significant relationship between lower SES, later prenatal diagnosis of trisomy, and higher live birth rate of T21 in Victoria.

Quality management of nuchal translucency ultrasound measurement in Australia.

BACKGROUND: Nuchal translucency measurement has an established role in first trimester screening. Accurate measurement requires that technical guidelines are followed. Performance can be monitored by auditing the distribution of measurements obtained in a series of cases. AIMS: The primary aim is to develop an accessible, theory-based educational program for individuals whose distribution of measurements at audit falls outside an acceptable range, and assess operator performance following this intervention. MATERIALS AND METHODS: Operators whose nuchal translucency measurement distributions fall outside a normal range (38-65% above the median) were expected to undergo a teleconference tutorial. Accessible from anywhere in Australia, the one hour tutorials were run by a senior sonographer (to explain technical ultrasound aspects) and the audit program manager (to explain the audit process). RESULTS: In 2011, 83 operators attended the teleconference tutorials. Compared to a random comparison group of operators meeting standard in 2011, teleconference tutorial attendees were significantly more likely to: (i) operate in rural or regional, rather than metropolitan, centres (P = 0.001); (ii) be less experienced (P < 0.0005); and (iii) have lower annual scan numbers (P = 0.0012). Improvement in nuchal translucency measurement quality was seen after one audit cycle and was maintained over subsequent years. The mean percentage of the study cohort reaching standard over the five-year audit was 77.8% which was not statistically different from the average for the comparison cohort of all other audited operators (79.3%; P = 0.61). CONCLUSIONS: Teleconference tutorials are a convenient, accessible and effective way to obtain immediate and sustained improvement in operator performance.

The Association of Sonographic Evidence of Adenomyosis with Severe Endometriosis and Gene Expression in Eutopic Endometrium.

STUDY OBJECTIVE: To examine the presence of sonographic evidence of adenomyosis (SEOA) in patients undergoing laparoscopic surgery for the investigation of endometriosis and to assess if there is an association between SEOA and endometriosis severity. Using gene expression analysis, we also aimed to determine if gene expression in eutopic endometria differed in patients with and without adenomyosis. DESIGN: A prospective study (Canadian Task Force classification II-2). SETTING: A tertiary medical center. PATIENTS: Reproductive-age women who underwent laparoscopic surgery after presenting to a pelvic pain-focused gynecology clinic. INTERVENTIONS: Endometrial tissue, detailed patient questionnaires, pathology, and surgical notes were collected. Sonographic data from tertiary ultrasounds performed up to 12 months before surgery were retrospectively added (n = 234, researchers blinded to surgical and pathological findings). Gene array data from endometrial biopsies (n = 41) were used to analyze differential gene expression; patients were divided into 2 groups according to the presence or absence of SEOA. MEASUREMENTS AND MAIN RESULTS: Of the 588 patients recruited, 234 (40%) had an available pelvic scan and were included in this study. The average age of the included women was 30.6 years, with 35% having SEOA. Patients with SEOA were 5.4 years older (p = .02). There was no significant difference in the rates of endometriosis between groups; however, patients with SEOA were more likely to have stage IV endometriosis (41% vs 9.8%, p <.001). Patients with SEOA were also more likely to have other markers of severe endometriosis such as endometriomas and deep infiltrating endometriosis (p <.001). No significant difference was observed in endometrial gene expression between adenomyosis cases and controls after adjusting for menstrual c`ycle phases and the presence/absence of endometriosis. CONCLUSION: Sonographic features of adenomyosis may be included as a component of the clinical assessment when attempting to predict the presence of severe endometriosis. No differences in gene expression were observed. Further research is needed to characterize uterine adenomyosis and to explore molecular pathways involved in its pathogenesis.

Non-Invasive Prenatal Testing for Sex Chromosome Aneuploidy in Routine Clinical Practice.

OBJECTIVES: To assess the accuracy of non-invasive prenatal testing (NIPT) for sex chromosome aneuploidy (SCA) in routine clinical practice and to review counselling and sonographic issues arising in SCA cases. METHODS: Three specialist Australian obstetric ultrasound and prenatal diagnosis practices offering NIPT after 10 weeks' gestation participated in this study. NIPT was reported for chromosomes 21, 18, 13, X, and Y. RESULTS: NIPT screening was performed in 5,267 singleton pregnancies. The odds of being affected given a positive screening result (OAPR) was lowest for SCAs, most notably for monosomy X (20%). Fewer women underwent invasive prenatal testing when counselled regarding a high risk for SCA (65.5%) compared with those who had a high risk for another aneuploidy (85%). The positive screening rate of NIPT including SCA was 2.3%, but 1.2% if only the autosomal trisomies were included in the panel. CONCLUSION: The addition of SCA testing to NIPT doubles the positive screening rate. The OAPR for SCAs (most notably for monosomy X) is reduced compared with the autosomal trisomies. Clinicians need a more extensive discussion with women prior to the inclusion of the X and Y chromosomes in the NIPT panel, given the complexity in counselling regarding further management and the additional anxiety that these abnormal results may cause. A benefit of sex chromosome analysis is an improvement in antenatal diagnosis of some disorders of sexual development.

Factors affecting cell-free DNA fetal fraction and the consequences for test accuracy.

INTRODUCTION: Biological factors are known to influence the fetal fraction (FF) of cell-free DNA and may also influence the accuracy of non-invasive prenatal testing. MATERIAL AND METHODS: NIPT from 5267 mixed risk women across three specialist clinics in Australia were analyzed. Multivariable regression analysis was used to determine whether maternal characteristics, ultrasound, and placental biomarkers affect FF and test accuracy. RESULTS: FF ranged from 4% to 37% (mean 11.6%). Body mass index (BMI), gestation, and placental biomarkers were found to be significant factors associated with FF. For each unit increase in BMI, the logarithmically transformed FF, (lnFF), mean value decreased by 0.027. Each week increases in gestation, lnFF increased by 0.023. Each unit increase in free BhCG, PAPPA, and PlGF, the lnFF increased by 0.065, 0.050, and 0.17, respectively. There was no significant association between FF with either maternal age or nuchal translucency. The false-positive cases and one false-negative case did not have lower FF than the true-positive cases. DISCUSSION: The fetal fraction in maternal plasma cfDNA increased with gestational age, serum pregnancy-associated plasma protein A (PAPP-A), ß-hCG, and PlGF and decreased with increasing maternal BMI. There was no significant correlation between low FF and test accuracy, when FF was above 4%.

Right-sided aortic arch in the age of microarray.

OBJECTIVE: For fetuses with a diagnosis of right aortic arch and normal cardiac anatomy, we aimed to establish the frequency of chromosomal anomaly diagnosed with single nucleotide polymorphism microarray analysis, particularly focusing on microduplications or microdeletions which would have gone undetected by conventional karyotyping and six-probe fish (13,18,21, X,Y, TUPLE). METHOD: Retrospective study of fetal ultrasounds between 2011 and 2016 in an Australian tertiary referral centre. Outcomes of interest were survival and postnatal surgery for vascular ring. RESULTS: Thirty patients were identified; 24 were apparently isolated. Chromosomal anomalies were identified in eight fetuses (32%) of 25 who had chromosomal testing. The rate in isolated cases was 11% and 56% in non-isolated cases. The 22q11.2 deletion was identified in three fetuses (12%). Microarray identified copy number variants of potential clinical significance in four additional fetuses (16%). Long continuous stretches of homozygosity were identified in one fetus with cerebellar hypoplasia potentially identifying the loci for recessive mutations. Surgery for vascular ring was performed on seven infants (25%) CONCLUSION: Microarray detected clinically significant chromosomal anomalies in fetuses with right aortic arch that would not be detected with conventional karyotyping. Prenatal counselling should include the chance of postnatal surgery and the importance of long-term follow-up. © 2017 John Wiley & Sons, Ltd.

Noninvasive prenatal testing in routine clinical practice--an audit of NIPT and combined first-trimester screening in an unselected Australian population.

BACKGROUND: There are limited data regarding noninvasive prenatal testing (NIPT) in low-risk populations, and the ideal aneuploidy screening model for a pregnant population has yet to be established. AIMS: To assess the implementation of NIPT into clinical practice utilising both first- and second-line screening models. MATERIALS AND METHODS: Three private practices specialising in obstetric ultrasound and prenatal diagnosis in Australia offered NIPT as a first-line test, ideally followed by combined first-trimester screening (cFTS), or as a second-line test following cFTS, particularly in those with a calculated risk between 1:50 and 1:1000. RESULTS: NIPT screening was performed in 5267 women and as a first-line screening method in 3359 (63.8%). Trisomies 21 and 13 detection was 100% and 88% for trisomy 18. Of cases with known karyotypes, the positive predictive value (PPV) of the test was highest for trisomy 21 (97.7%) and lowest for monosomy X (25%). Ultrasound detection of fetal structural abnormality resulted in the detection of five additional chromosome abnormalities, two of which had high-risk cFTS results. For all chromosomal abnormalities, NIPT alone detected 93.4%, a contingent model detected 81.8% (P = 0.097), and cFTS alone detected 65.9% (P < 0.005). CONCLUSIONS: NIPT achieved 100% T21 detection and had a higher DR of all aneuploidy when used as a first-line test. Given the false-positive rate for all aneuploidies, NIPT is an advanced screening test, rather than a diagnostic test. The benefit of additional cFTS was the detection of fetal structural abnormalities and some unusual chromosomal abnormalities.

Auditing ultrasound assessment of fetal nuchal translucency thickness: a review of Australian National Data 2002-2008.

BACKGROUND: Nuchal translucency (NT) measurement is the ultrasound component of first trimester combined screening for Down syndrome. In 2002, a NT ultrasound education and monitoring program was established in Australia. Between 2002 and 2008, a total of 728,502 NT scans were audited through this process. OVERALL AIM: To audit the availability and performance of certified operators measuring NT following implementation of the Australian education and monitoring program in 2002. METHODS: Retrospective review of the central database that is used to monitor performance of individuals and practices performing NT scans in both public and private practice settings throughout Australia between 2002 and 2008. The performance of operators was assessed by a widely used international standard - that 40-60% of NT measurements should be above the median value for gestational age. RESULTS: The number of certified operators has increased (from 184 in 2002 to 477 in 2008). There is wide variation between states in the number of operators per birth. The percentage of certified operators with a measurement distribution meeting the international standard has increased from 40% in 2002 to 55% in 2008. Greatest improvement has been seen in operators performing 30-199 scans per year. There has been no overall improvement in performance over the last three audit cycles. CONCLUSIONS: The number of operators certified to perform the NT scan has increased since 2002, although availability in some states remains low. An initial improvement in performance of operators appears to have reached a plateau. It is time to become more proactive in engaging operators in the audit cycle.