Prenatal Diagnosis Of Chromosomal Abnormalities Research Articles

Clinical value of screening prenatal ultrasound combined with chromosomal microarrays in prenatal diagnosis of chromosomal abnormalities

Objective To evaluate the clinical value of ultrasound findings in the screening of fetal chromosomal abnormalities and the analysis of risk factors for chromosome microarray analysis (CMA) abnormalities. Methods We retrospectively analyzed the datasets of 15,899 pregnant women who underwent prenatal evaluations at Affiliated Maternity and Child Health Care Hospital of Nantong University between August 2018 and December 2022. Everyone underwent ultrasound screening, and those with abnormal findings underwent CMA to identify chromosomal abnormalities. Results The detection rates for isolated ultrasound anomalies and combined ultrasound and CMA anomalies were 11.81% (1877/15,899) and 2.40% (381/15,899), respectively. Among all ultrasound abnormalities, detection rates for isolated ultrasound soft marker anomalies, isolated structural abnormalities, and both ultrasound soft marker anomalies with structural abnormalities were 82.91% (1872/2258), 15.99% (361/2258), and 1.11% (25/2258), respectively. The detection rate of abnormal chromosomes in pregnant women with abnormal ultrasound results was 16.87% (381/2258). The detection rates were 13.33% in cases with two or more ultrasound soft markers anomalies, 47.37% for two or more structural anomalies, and 48.00% for concomitant ultrasound soft marker and structural anomalies. Conclusions Enhanced detection rates of chromosomal anomalies in fetal malformations are achieved with specific ultrasound findings (NT thickening, cardiovascular abnormalities, and multiple soft markers) or when combined with high-risk factors (advanced maternal age, familial history, parental chromosomal anomalies, etc.). When the maternal age is over 35 and with ≥2 ultrasound soft marker anomalies accompanied with any high-risk factors, CMA testing can aid in the diagnosis of prenatal chromosomal abnormalities.

Screening and diagnosis of chromosomal abnormalities in twin pregnancy.

Twin pregnancies are at an increased risk of adverse pregnancy and perinatal outcome as compared to singleton gestations, mainly as the consequence of the higher rate of preterm birth, chromosomal as well as structural anomalies, placental abnormalities, and complications unique to monochorionic placentation. Screening for chromosomal anomalies poses diagnostic and management challenges when applied to twin pregnancies. The recent implementation of cell-free fetal DNA (cffDNA) in clinical practice raises the questions whether a more accurate test should be offered to twin pregnancies in view of the higher false positive rate of traditional screening and the higher risk of fetal loss following amniocentesis or chorionic villus sampling (CVS) in multiple gestations. Finally, twin pregnancies require a tailored approach for aneuploidy screening, such as nuchal translucency (NT) or crown rump length discordance, discordant fetal anomalies, or monoamniotic gestations. The present review aims to provide an up-to-date critical appraisal of screening and prenatal diagnosis of chromosomal abnormalities in twin pregnancies.

Prenatal Diagnosis of Chromosome Abnormalities: 21 Years of Experience

Prenatal Diagnosis of Chromosome Abnormalities: 21 Years of Experience

Application of the BACs-on-Beads assay for the prenatal diagnosis of chromosomal abnormalities in Quanzhou, China

BackgroundAn increasing number of techniques have been used for prenatal diagnosis of genetic abnormalities. Our initial objective was to explore the value of the BACs-on-Beads (BoBs) assay for the prenatal diagnosis of aneuploidies and microdeletion/microduplication syndromes in Quanzhou, Southeast China.MethodsA total of 1409 pregnant women with high-risk factors for chromosomal abnormalities admitted to Quanzhou Women’s and Children’s Hospital were enrolled in this study. BoBs assays and karyotype analyses were conducted for all subjects. Subsequently, chromosome microarray analysis (CMA) or fluorescence in situ hybridization (FISH) was performed to validate the findings.ResultsIn this study, karyotype analysis and BoBs assay failed in 4 cases, and 2 cases, respectively. A total of 1403 cases were successfully analyzed, with success rates of 99.72% (1405/1409) and 99.85% (1407/1409) for karyotype analysis and Bobs assay, respectively. BoBs assay rapidly detected chromosomal aneuploidies in line with the karyotyping data. Additionally, 23 cases of microdeletions/microduplications were detected by BoBs assay but missed by karyotyping, including 22q11.2 microdeletions/microduplications, 5p15.32p15.33 microdeletion, Xp22.31 microdeletions/microduplications, Xq27.3 microdeletion, and Yp11.2 and Yq11.22q11.222 microduplication. In comparison with karyotyping, fewer mosaicisms were identified by BoBs assay. A high detection rate of chromosomal abnormalities was observed in the high-risk group during noninvasive prenatal testing (NIPT) (41.72%) and the abnormal ultrasound group (13.43%).ConclusionsBoBs assay can be used for the rapid and efficient prenatal diagnosis of common aneuploidies and microdeletion/microduplication syndromes. Moreover, the combined use of BoBs assay and karyotyping in prenatal diagnosis may allow for a more effective detection of chromosomal abnormalities.

Antenatal detection of chromosomal abnormalities combining QF-PCR and cytogenetic analysis

Aim: To compare the diagnostic values and limitations of quantitative fluorescent polymerase chain reaction (QF-PCR) and conventional cytogenetic analysis in prenatal diagnosis of chromosomal abnormalities. Methods: A prospective study included simultaneous QF-PCR and cytogenetic analysis of 133 prenatal samples routinely obtained by amniocentesis or chorionic villus sampling (CVS). Additionally, QF-PCR analysis was performed on 14 tissue samples collected after termination of pregnancy (TOP) for which karyotyping could not be performed due to culture failure. Results: Among 133 analyzed prenatal samples, chromosomal abnormalities were diagnosed in 12 cases (9%), including 10 cases of numerical chromosomal aberrations and two cases with unbalanced structural rearrangements. Nine out of 12 chromosomal abnormalities were also detected with QF-PCR. However, all cases of major aneuploidies were successfully disclosed with QF-PCR, resulting in 100% detection rate for chromosomes 21, 18, 13, X and Y. Using a set of markers specific for chromosomes 21, 18 and 13, QF-PCR analysis of tissues collected after TOP revealed chromosomopathy in 21.4% of cases (two cases of trisomy 18 and one triploidy). A comparison of STR markers confirmed monozygosity in two monochorionic/diamniotic twin pregnancies. Conclusion: QF-PCR has been shown as a rapid and reliable method for prenatal diagnosis of the most common chromosomal aneuploidies, and as an adequate alternative to conventional karyotyping in cases where cytogenetic analysis is not possible due to failure of culturing process. However, conventional cytogenetics still presents a gold standard for the detection of structural aberrations and rare aneuploidies.

Frequency of Prenatal Diagnosis of Chromosomal Abnormalities in Amniotic Fluid of Pregnant Women

Frequency of Prenatal Diagnosis of Chromosomal Abnormalities in Amniotic Fluid of Pregnant Women

Simultaneous analysis of bisphenol A fractions in maternal and fetal compartments in early second trimester of pregnancy.

Background Bisphenol A (BPA) is an estrogenic, endocrine-disrupting compound widely used in the industry. It is also a ubiquitous environmental pollutant. Its presence was confirmed in human fetuses, which results from maternal exposure during pregnancy. The mechanisms behind maternal-fetal transfer, and relationships between pregnant women and fetal exposures remain unclear. The aim of this study was to assess the impact of maternal exposure to BPA on the exposure of the fetus. Methods Maternal plasma and amniotic fluid samples were collected from 52 pregnant women undergoing amniocentesis for prenatal diagnosis of chromosomal abnormalities. BPA was measured by gas chromatography-mass spectrometry (GC-MS). The permeability factor - a ratio of fetal-to-maternal BPA concentration - was used as a measure delineating the transplacental transfer of BPA. Results The median concentration of maternal plasma BPA was 8 times higher than the total BPA concentration in the amniotic fluid (8.69 ng/mL, range: 4.3 ng/mL-55.3 ng/mL vs. median 1.03 ng/mL, range: 0.3 ng/mL-10.1 ng/mL). There was no direct relationship between the levels of BPA in maternal plasma and amniotic fluid levels. The permeability factor, in turn, negatively correlated with fetal development (birth weight) (R = -0.54, P < 0.001). Conclusion Our results suggest that the risk of fetal BPA exposure depends on placental BPA permeability rather than the levels of maternal BPA plasma concentration and support general recommendations to become aware and avoid BPA-containing products.

Молекулярное кариотипирование в практике пренатальной диагностики: опыт, проблемы, перспективы

В последнее время происходит активное внедрение высокоразрешающих методов диагностики для выявления хромосомных аномалий у человека. Так, использование микрочиповой диагностики (aCGH) позволяет выявлять хромосомные аномалии у 6 % плодов с нормальным кариотипом, определённым стандартными цитогенетическими методами. При этом для пренатальной диагностики aCGH используется в значительно меньших объемах. В первую очередь это обусловлено получением большого объема информации и сложностями её интерпретации. В настоящей работе приводятся результаты использования aCGH для пренатальной диагностики в НИИ медицинской генетики Томского НИМЦ. Исследованы 44 образца плодного материала методом aCGH. В 20 случаях (45 %) идентифицирован геномный дисбаланс, сбалансированный кариотип был выявлен в 21 образце (48 %). В трех случаях (7 %) результат не был получен вследствие недостаточного количества или низкого качества биологического материала. Среди 20 случаев с хромосомными аномалиями было 4 образца с анеуплоидиями и 16 образцов с вариациями числа копий ДНК (CNV), из них 13 делеций и 10 дупликаций. Все CNV, выявленные в результате исследования, не представлены или представлены единичными случаями в базе данных DGV. По клинической значимости выявленные CNV распределились следующим образом: 5 аномалий с неясной клинической значимостью, 5 вероятно патогенных и 11 патогенных. Патогенные CNV были представлены 7 делециями и 4 дупликациями, идентифицированными в 10 образцах. Кроме «целевых» патогенных CNV, выявляются и так называемые случайные патогенетически значимые CNV. Случайные находки характерны для всех широкогогеномных и полногеномных исследований и вызывают сложности при медико-генетическом консультировании, связанные с информированием пациентов и возможным прерыванием беременности. В настоящем исследовании было выявлено по пять CNV (24 %), относящихся к группам случайных патогенных и с неясной клинической значимостью. Результаты настоящей работы свидетельствуют о необходимости использования современных молекулярно-цитогенетических методов для пренатальной диагностики хромосомных аномалий. При этом необходимо учитывать возникновение новых методических и этических вопросов, которые наиболее остро стоят при использовании этих методов в пренатальной диагностике. Recently, there has been an active introduction of high-resolution diagnostic methods for detecting chromosomal abnormalities in humans. Thus, the use of microarray diagnostics allows detecting 6% more chromosomal abnormalities in fetuses with a normal karyotype based on the results of standard cytogenetic methods. At the same time, as part of the prenatal diagnosis, aCGH is used in much smaller amounts. This is primarily due to the receipt of a large amount of information and difficulties with its interpretation. This paper presents the results of using the aCGH method in prenatal diagnosis at the Research Institute of Medical Genetics of the Tomsk National Research Medical Center. In the framework of prenatal diagnosis, 44 samples of fetal material were examined using the aCGH method. Prenatal diagnosis using microarray in 20 cases (45%) allowed to identify chromosomal abnormalities, a balanced karyotype was detected in 21 samples (48%). In three cases (7%) the result was not obtained due to insufficient quantity or low quality of the biological material. Among the 20 cases with chromosomal abnormalities, 4 samples with aneuploidy and 16 samples with CNV. In 16 samples of fetal material without aneuploidy, 13 deletions and 10 duplications were identified. All the adjustments included in this list are not represented or represented by isolated cases in the Database of Genomic Variants. When analyzing the clinical significance of the CNV, were identified 11 pathogenic, 5 probably pathogenic and 5 CNV with uncertain significance. Pathogenic rearrangements were represented by 7 deletions and 4 duplications identified in 10 samples. In addition to the “Primary Finding” of pathogenic CNVs, so-called “Incidental Finding” of pathogenetically significant rearrangements are also detected. The identification of “Incidental Finding” is characteristic of all genome-wide studies and leads to the emergence of ethical issues related to informing patients and the possible termination of pregnancy. In the present study, five “Incidental Finding” pathogenic CNVs and five rearrangements with uncertain significance were identified. The results of this work indicate the need to use modern molecular cytogenetic methods for the prenatal diagnosis of chromosomal abnormalities. It is necessary to take into account the emergence of new methodological and ethical issues that are most acute when using these methods in prenatal diagnosis.

Validity of chromosomal aneuploidies testing during pregnancy: A comparison of karyotype, interphase-FISH and QF-PCR techniques

Prenatal diagnosis of chromosomal abnormalities is an important challenge for pregnancy management has relied on conventional cytogenetic analysis of cultured amniotic fluid, chorionic villi, or fetal blood for a long time. New molecular methods included FISH and QF-PCR on uncultured amniotic fluid or chorionic villi have been applied recently for the rapid aneuploidies detection in chromosomes 13, 18, 21, X and Y. Both molecular methods are quicker than Karyotype as conventional cytogenetic technique. The advantages of QF-PCR include detection of trisomy, mosaicism and maternal cell contamination. This technique is more cost effective, less labor-intensive and more suitable for large sample numbers in comparison to FISH. FISH is a robust method and extensively validated. It detects mosaicism and trisomy. Herein we aimed to assess prenatal diagnosis of aneuploidies in chromosomes 13, 18, 21, X and Y. For this aim, amniotic fluid samples have collected for analysis of common chromosomal aneuploidies using Karyotype, FISH and QF-PCR methods. 69 samples have obtained by amniocentesis from 15th-18th week of pregnancies and subjected for comparative analysis by three techniques: FISH, QF, and Karyotype with the same accuracy concerning the detection of trisomy 13, 18, 21, and sex chromosomes X and Y. We conclude that molecular techniques are rapid-reliable methods for analysis of chromosome number in uncultured amniotic fluid. Nevertheless, QF-PCR and FISH are an alternative option, if timing is a limiting factor. This report in line with previous studies emphasizes the importance of molecular techniques for the prenatal identification of the numerical chromosomal abnormalities and ultimately management of pregnancies saving patients from anxiety.

Эффективность пренатальной диагностики синдрома Дауна в шести областях Центрального и Юго-Восточного регионов Украины

Chromosomal aneuploidy (CA), having an incidence rate of 6-8 per 1000 live births, holds a special place in the structure of congenital and hereditary pathology. Among the common CA, trisomy 21 chromosomes (T21) is the most frequently found (its incidence rate in the general population amounts to 1:700–800 live births). The objective: to study the efficiency of prenatal screening of CA (Down’s syndrome, DS) in the areas under the Center’s operational activity in the period of 2010-2015; To estimate the actual prevalence of DS in terms of born and prenatally diagnosed, eliminated fetuses with T21; On the basis of retrospective analysis of indications for prenatal karyotyping, in all detected cases of DS, to specify their structure and incidence rate; Based on data from medical literature, to make a comparative analysis with similar studies in different countries around the world. Patients and methods. Over the six years (2010–2015) we have performed 3,137 invasive prenatal interventions, among which are 720 chorionic villus biopsies, 929 placententesises, and 1,488 amniocentesis of pregnant women having a high risk of CA, who were seeking medical help from our center whose operational activity covers 6 provinces (oblasts). Results. From 3,137 prenatally karyotyped studies, there have been found only 558 cases of fetal CA, including 288 fetuses with T21. A retrospective analysis of the structure of indications for invasive prenatal diagnosis in 288 pregnant women, having fetuses with prenatally detected DS, is presented as follows: – separate: only 40-aged and above mothers – 4 (1.38%); Ultrasound (US)-findings (anomalies and markers of CA) – 192 (69.5%); High biochemical risk of CA – 2 (0.7%). – combined: the mother’s age is 40 and above + US findings – 36 (13%); The mother’s age is 40 and above + US and biochemical (BC) markers – 8 (2.8%); Ultrasound findings + positive BC test – 32 (11.5%). Delivery of the previous child with DS by a pregnant woman under 40 years with no ultrasound and BC markers – 1 (0.34%). In total, ultrasound findings (anomalies and markers of CA) were found in 97.5% of cases of prenatally detected fetuses with DS. The index of prenatal detection of fetuses with Down syndrome of all registered karyotyped cases of T21 (pre- and postnatal) in the Dnepropetrovskaya oblast corresponds to the average European level - 65%, (in the areas of the center’s operational activity – 37.7%). Taking into account 242 cases of DS in fetuses aborted prior 22 weeks of gestation, the actual prevalence of T21 in case of their birth would be 1:766 (13 per 10.000 infants). Conclusions. Prevalence of Down syndrome among newborns in the Dnepropetrovskaya oblast as a result of prenatal diagnosis of chromosomal abnormalities makes 1: 1257, which is 1.8 times lower than the incidence in the average population (1:700); In other areas covered by the center’s consulting and diagnostic activity this rate is 1.1–1.55 times lower than that of the population one. In the absence of the existing system of prenatal diagnosis of Down syndrome, its average prevalence in these provinces would correspond to that of the general population 1:766 newborns. Key words: сhromosomal abnormalities, Down syndrome, prenatal screening strategies, ultrasound diagnosis, invasive prenatal diagnosis, ultrasound markers.

Diagnóstico prenatal de anomalías cromosómicas Biopsia de vellosidades coriales y amniocentesis para cariotipo fetal

Introducción: El diagnóstico prenatal temprano de anomalías cromosómicas requiere de técnicas invasivas, como la biopsia de vellosidades coriales (BVC) y la amniocentesis (AMC), con el fin de obtener células fetales, cultivarlas y obtener el cariotipo en los fetos con riesgo alto para estas anomalías, identificadas mediante marcadores ecográficos y bioquímicos desde las 11 semanas. Reportamos nuestra experiencia hasta junio del año 2016. Diseño: Estudio descriptivo longitudinal. Institución: Instituto Latinoamericano de Salud Reproductiva (ILSAR), Lima, Perú. Participantes: Fetos de primer y segundo trimestres del embarazo. Intervenciones: Se analizó los resultados del estudio de 400 fetos que cursaban el primer y segundo trimestre y que tenían riesgo alto para anomalías cromosómicas (mayor de 1/270 inicialmente y 1/100 desde el año 2012), resultado cuantificado utilizando la base de datos del Fetal Test de España más el resultado de los marcadores bioquímicos (riesgo combinado). El análisis del cariotipo fetal se realizó en muestras obtenidas por medio de 338 amniocentesis genéticas y 62 biopsias de vellosidades coriales realizadas durante el período comprendido de enero 2003 a junio 2016 en nuestro centro ILSAR. Principales medidas de resultados: Presencia de arcadores ecográficos y normalidad de los cariotipos. Resultados: Los marcadores ecográficos encontrados con mayor frecuencia fueron: higroma quístico (35,8%), translucencia nucal aumentada (13%), ductus venoso con onda de velocidad de flujo anormal (8,5%), dos o más marcadores asociados a anomalías fetales (13,7%). De 400 muestras estudiadas, 141 (35%) fueron cariotipos anormales: 64 (45%) T21, 35 (25%) T18, 21 (15%) 45X, 7 (5%) T13, 14 (10%) otras anomalías. No hubo complicación importante alguna atribuida al procedimiento invasivo. Conclusiones: En los fetos con riesgo alto para anomalías cromosómicas estudiados, el 35% tuvo cariotipo anormal, siendo las más frecuentes las trisomías de los cromosomas 21 y 18, seguidas de la monosomía del cromosoma X. El higroma quístico, la translucencia nucal aumentada y la presencia de 2 o más marcadores asociados a anomalías fetales fueron los hallazgos más frecuentes en la determinación del riesgo ecográfico. El higroma quístico mostró el mayor valor predictivo para anomalías cromosómicas.

Amniocentesis

AbstractAmniocentesis is the most common invasive prenatal diagnostic procedure worldwide. It is a technique of withdrawing amniotic fluid from the uterine cavity using a needle, via a transabdominal approach, under continuous ultrasound guidance, in order to obtain a sample of fetal exfoliated cells, transudates, urine, or secretions. The amniotic fluid contains amniocytes and fetal epithelial cells. Amniotic fluid can be tested directly or grown in culture for various chromosomal, bio-chemical, molecular, and microbial studies. Amniocentesis for genetic testing is generally performed between the gestational age of 16 and 20 weeks. Diagnostic amniocentesis is commonly used for prenatal diagnosis of chromosomal abnormalities, single gene disorders, fetal infection, and intra-amniotic inflammation. Common indications cited are advanced maternal age, positive maternal screening results for aneuploidy, structural abnormality on ultrasound, and inconclusive or positive noninvasive prenatal testing. Pre-procedure counseling and screening ultrasound should always be done before subjecting a woman to amniocentesis. Complete procedure is performed under ultrasound guidance with continuous visualization of the needle under proper aseptic conditions. Post-procedure follow-up includes documentation of fetal viability immediately after the procedure by ultrasound studies, anti-D immunoglobulin (300 g) to be administered to RhD negative women, and house rest for 24 h.

Application of chromosomal microarray analysis in prenatal diagnosis of fetal growth restriction.

To investigate the clinical value of chromosomal microarray analysis (CMA) in the prenatal diagnosis of chromosomal abnormalities in fetal growth restriction (FGR) cases. The ultrasound findings of 107 FGR cases subjected to invasive prenatal diagnostic testing from March 2013 to October 2015 were retrospectively reviewed. Karyotyping was performed in all cases, and CMA was performed in 80 cases. In our study, karyotype analysis identified chromosomal aberrations in 9.3% (10/107) of the cases, while CMA detected abnormalities in 18.8% (15/80) of the cases. CMA achieved a 11.4% detection rate of chromosomal abnormalities among FGR cases with a normal karyotype. Among 53 FGR cases without malformations, CMA increased (9.4%; 95%CI, 1.6%-17.3%) the detection rate of chromosomal abnormalities. CMA identified more chromosomal abnormalities (50.0%; 95%CI, 19.0%-81.0%) than karyotyping (30.0%; 95%CI, 7.0%-65.0%) among the cases diagnosed during the second trimester. Further, the detection rate in cases with asymmetric FGR was higher with CMA (33.3%; 95%CI, 10.0%-65.0%) than with karyotyping (16.7 %; 95%CI, 2.0%-48.0%). Our study highlights the added value of CMA compared with karyotyping in evaluation of asymmetric FGR cases diagnosed during the second trimester without sonographic anomalies. © 2016 John Wiley & Sons, Ltd.

Non-invasive prenatal cell-free fetal DNA testing for down syndrome and other chromosomal abnormalities

Background: Chorionic villus sampling and amniocentesis as definitive diagnostic procedures represent a gold standard for prenatal diagnosis of chromosomal abnormalities. The methods are invasive and lead to a miscarriage and fetal loss in approximately 0.5–1 %. Non-invasive prenatal DNA testing (NIPT) is based on the analysis of cell-free fetal DNA from maternal blood. It represents a highly accurate screening test for detecting the most common fetal chromosomal abnormalities. In our study we present the results of NIPT testing in the Diagnostic Center Strah, Slovenia, over the last 3 years.Methods: In our study, 123 pregnant women from 11th to 18th week of pregnancy were included. All of them had First trimester assessment of risk for trisomy 21, done before NIPT testing.Results: 5 of total 6 high-risk NIPT cases (including 3 cases of Down syndrome and 2 cases of Klinefelter’s syndrome) were confirmed by fetal karyotyping. One case–Edwards syndrome was false positive. Patau syndrome, triple X syndrome or Turner syndrome were not observed in any of the cases. Furthermore, there were no false negative cases reported. In general, NIPT testing had 100 % sensitivity (95 % confidence interval: 46.29 %–100.00 %) and 98.95 % specificity (95 % confidence interval: 93.44 %–99.95 %). In determining Down syndrome alone, specificity (95 % confidence interval: 95.25 %- 100.00 %) and sensitivity (95 % confidence interval: 31.00 %–100.00 %) turned out to be 100 %. In 2015, the average turnaround time for analysis was 8.3 days from the day when the sample was taken. Repeated blood sampling was required in 2 cases (redraw rate = 1.6 %).Conclusions: Our results confirm that NIPT represents a fast, safe and highly accurate advanced screening test for most common chromosomal abnormalities. In current clinical practice, NIPT would significantly decrease the number of unnecessary invasive procedures and the rate of fetal loss caused by invasive diagnostics.

How to perform an amniocentesis.

Amniocentesis is a technique for withdrawing amniotic fluid from the uterine cavity using a needle, via a transabdominal approach and under continuous ultrasound guidance, in order to obtain a sample of fetal exfoliated cells, transudates, urine or secretions. It can be performed from 16 weeks of pregnancy onwards, with various chromosomal, biochemical, molecular and microbial studies being performed on the amniotic fluid sample. The most common reasons for the procedure are to enable prenatal diagnosis of chromosomal abnormalities, single gene disorders, fetal infection and intra-amniotic inflammation, as well as to assess fetal lung maturity and blood or platelet type. The procedure has a risk of fetal loss of approximately 0.5% (range, 0.06–1%)1 when performed in the second trimester, after the amniotic membrane has fused with the chorion; there is also a risk of amniotic fluid leakage (approximately 0.3% of cases) and other rare complications, such as placental hemorrhage, intra-amniotic infection, abdominal wall hematoma and fetal lesion. There is an important lack of good-quality evidence to support most recommendations for the procedure, and a recent review suggested that operators should use those methods and technique modifications with which they are most familiar when performing an amniocentesis2. The aim of this summary article and the full version, included as supplementary material online, is to describe the amniocentesis technique, presenting a practical guideline for its performance. We also describe the use of a Vacutainer® (BD Vacutainer Systems, Plymouth, UK) aspiration system in order to produce a continuous vacuum for amniotic fluid aspiration as an alternative to using manually operated syringes.

Karyotype versus genomic hybridization for the prenatal diagnosis of chromosomal abnormalities: a metaanalysis

The aim of this study was to determine the diagnostic accuracy of comparative genomic hybridization (CGH) compared with karyotyping for the detection of numerical and structural chromosomal alterations in prenatal diagnosis. A metaanalysis was performed using searches of PubMed, EMBASE, CENTRAL, Cochrane Register of Diagnostic Test Accuracy Studies, Google Scholar, gray literature, and reference manuals. No language restriction was imposed. We included cross-sectional, cohort, and case-control studies published from January 1980 through March 2014 in the analysis. Studies of pregnant women who received chorionic villus biopsies, amniocentesis, or cordocentesis and then underwent CGH and karyotype analysis were included. Two independent reviewers assessed each study by title, abstract, and full text before its inclusion in the analysis. Methodological quality was assessed using QUADAS2, and a third reviewer resolved any disagreement. Conclusions were obtained through tests (sensitivity, specificity, and likelihood ratios) for the presence of numerical and structural chromosomal abnormalities. The reference used for these calculations was the presence of any abnormalities in either of the 2 tests (karyotype or CGH), although it should be noted that in most cases, the karyotyping test had a lower yield compared with CGH. Statistical analysis was performed in RevMan 5.2 and the OpenMeta[Analyst] program. In all, 137 articles were found, and 6 were selected for inclusion in the systematic review. Five were included in the metaanalysis. According to the QUADAS2 analysis of methodology quality, there is an unclear risk for selection bias and reference and standard tests. In the other elements (flow, time, and applicability conditions), a low risk of bias was found. CGH findings were as follows: sensitivity 0.939 (95% confidence interval [CI], 0.838-0.979), I(2)= 82%; specificity 0.999 (95% CI, 0.998-1.000), I(2)= 0%; negative likelihood ratio 0.050 (95% CI, 0.015-0.173), I(2)= 0%; and positive likelihood ratio 1346.123 (95% CI, 389-4649), I(2)= 0%. Karyotype findings were as follows: sensitivity 0.626 (95% CI, 0.408-0.802), I(2)= 93%; specificity 0.999 (95% CI, 0.998-1.000), I(2)= 0%; negative likelihood ratio 0.351 (95% CI, 0.101-1.220), I(2)= 0%; and positive likelihood ratio 841 (95% CI, 226-3128), I(2)= 10%. This systematic review provides evidence of the relative advantage of using CGH in the prenatal diagnosis of chromosomal and structural abnormalities over karyotyping, demonstrating significantly higher sensitivity with similar specificity.

Parental decisions following prenatal diagnosis of chromosomal abnormalities: implications for genetic counseling practice in Japan.

Parental decision-making to terminate or continue a pregnancy was studied after prenatal diagnosis of a chromosome aneuploidy among a sample of patients around the city of Nagoya, Japan. A total of 1,051 amniocentesis cases at 15-18weeks of gestation were analyzed. Of these, 60 cases of chromosomal anomalies with aneuploidies were diagnosed by conventional cytogenetic analysis. Of the 45 diagnoses of autosomal chromosome aneuploidies, pregnancy was terminated in 93.3% of the cases. Of the 15 cases diagnosed with sex chromosome aneuploidy, pregnancy was terminated in 46.7%. Differences in parental decisions with respect to maternal age, gestational week at diagnosis, number of pregnancies per individual and existing number of children were not significant in patients diagnosed either with autosomal or sex chromosome aneuploidy. The findings indicate that when diagnosed with a chromosome aneuploidy in which a severe prognosis was expected, most couples decided to terminate the pregnancy in Japan. Implications of these findings for expanding the profession of genetic counseling are discussed and research recommendations are provided.

STR Markers in clinics: a rapid prenatal diagnosis by quantitative fluorescent-pcr for aneuploidies.

In the past few decades, prenatal diagnosis of fetal chromosomal abnormalities has relied on conventional cytogenetic analysis of cultured amniocytes, chorionic villi, or fetal blood. In recent years, the clinical validity of a newer technique, QF-PCR, to detect the common aneuploidies has been reported by a number of investigators. This technique has the advantage of providing rapid results for the diagnosis or exclusion of aneuploidy in chromosomes 13, 18, 21, X or Y. It is now possible to choose standard chromosome analysis or QF-PCR for the prenatal diagnosis of chromosomal abnormalities, or to perform both tests, depending on the clinical indication for testing. QF-PCR exploits the distribution of STR markers, 2-6bp tandem repeats, across the genome. This DNA marker is easily amplified by polymerase chain reaction (PCR) without the problem of differential amplification; that is, the PCR products for STRs are generally similar in amount, making analysis easier. An individual inherits one copy of an STR from each parent, which may or may not have similar repeat sizes. The number of repeats in STR markers can be highly variable among individuals, which make these STRs effective for diagnosis and human identification purposes. It has an added advantage of identifying maternal or paternal origin of nondysjunction. The establishment of QF-PCR has been initiated with the aim of providing rapid prenatal diagnostic service and to reduce anxiety of patients about their at risk pregnancies. For validation, we performed analysis on 100 confirmed cases of Down syndrome with the markers D21S1435, D21S11 and D21S1411, whose heterozygosity has been studied in North Indian population, with heterozygosity of 70.1%, 83.1% and 93.6% respectively. We observed 100% concordance with the clinical diagnosis as well as cytogenetic analysis. With these results we extended the methodology in prenatal services were chromosomal studies are very common for suspected Down syndrome pregnancies. However, in addition we included 2 more markers D21S1411 and D21S1413 for 21 chromosome, D13S238 and D13S631 for 13 chromosome, D18S391 for 18 chromosome and AMEL, XHPRT, X22 and SRY for sex chromosomes. Addition of 13, 18 and sex chromosomes marker were helpful at drawing conclusive reports for maternal contaminated samples and simultaneously to screen for rare aneuploides like 13, 18 trisomy and Klinefelter syndrome. The test was offered to the pregnancies with triple test positive as well as abnormal findings in ultrasonography. The source of DNA was 3 – 5 ml of amniotic fluid while in few cases chorionic villi sample. 190 pregnancies were studied to date, 3 pregnancies (1.6%) were turned to be Down syndrome positive while rest was negative for Down syndrome while 1 case was turned out to be homozygous for all 4 markers of 21chromosome in which we required additional markers to do reporting. However, karyotying showed this sample to be negative for Down syndrome. Rest all the finding was consistent with that of karyotyping results. The technique has its own advantage that can utilize the maternal blood contaminated samples, to add more, low volume of sample requirement and possibility to do reporting within 6 – 12 hours. Still we are working to record heterozygosity of rest of the 8 markers and to tune up the marker panel accordingly.

De la observación microscópica de los cromosomas en el cariotipo a los array-CGH en el diagnóstico prenatal

Introducción: el cariotipo ha sido la prueba de oro para el análisis cromosómico en el diagnóstico prenatal en los últimos cuarenta años; sin embargo, a partir del 2011 se publican múltiples artículos y los primeros meta-análisis que muestran posibles ventajas de los array-CGH (del inglés array-comparative genomic hibridization) sobre el cariotipo en el diagnóstico prenatal.Objetivo: hacer una reflexión acerca del uso de array-CGH en el diagnóstico prenatal y mostrar algunas de las potenciales ventajas y desventajas de esta prueba molecular con relación al cariotipo, así como su aplicación por obstetras, perinatólogos y especialistas en medicina materno-fetal.Conclusión: los a-CGH son una nueva alternativa en el análisis cromosómico en el diagnóstico prenatal en fetos con anomalías anatómicas; pueden usarse en todos los casos en que se justifique una intervención invasiva en el diagnóstico prenatal de alteraciones cromosómicas, y es probable que los array-CGH reemplacen al cariotipo en el diagnóstico prenatal en esta década.

Prenatal Diagnosis of Chromosome Abnormalities: Past, Present, and Future

For decades, conventional chromosome analysis using G-banded karyotyping has been the gold standard for detecting cytogenetic abnormalities in fetuses for prenatal diagnosis and pregnancy loss. Although chromosome studies easily identify such chromosome abnormalities as aneuploidy (gain or loss of an entire chromosome), balanced rearrangements, and large unbalanced structural rearrangements, they have limited resolution. Pathogenic copy number changes smaller than approximately 5–10 Mb are not detectable; however, recent advances in chromosomal microarray (CMA)2 analysis now allow the detection of chromosomal deletions and duplications at much higher resolutions (down to only a few kilobases, depending on the microarray), producing a higher diagnostic yield. In fact, a recently published study that compared standard karyotyping with postnatal CMA testing for patients with unexplained developmental delay, autism spectrum disorders, or multiple congenital anomalies demonstrated an increased diagnostic yield of about 12%–15% with CMA analysis, vs. 4% with karyotyping. These findings led to the recommendation by the American College of Medical Genetics that CMA testing replace chromosome analysis as the first-tier test for such patients (1, 2). Given these findings in the postnatal setting, the incremental diagnostic yields of CMA analysis and chromosome analysis are now being evaluated for prenatal genetic testing. Recent publications in the New England Journal of Medicine have described approaches to answering this question, not only with prenatal samples (3) but also with stillbirths (defined as pregnancy loss at or after 20 weeks' gestation) (4). The multicenter study by Wapner et al. successfully analyzed 4182 samples of amniotic fluid and chorionic villi with both chromosome and CMA analysis (3). The women were tested for indications that included advanced maternal age, a positive result in maternal-serum screening, and fetal anomalies detected on ultrasonography. CMA was equally efficacious in identifying all aneuploidies and unbalanced rearrangements that had been identified by karyotyping. …