BACKGROUND

Down syndrome or trisomy 21, the most common chromosomal disorder, results from the presence of a third copy of chromosome 21 and manifests as mild to moderate intellectual disability, growth retardation, congenital heart defects, gastrointestinal abnormalities, and characteristic facial features. Several methods have been used to screen for Down syndrome in the prenatal period, such as ultrasound, biomarkers, cell-free DNA testing, and combinations of these tests. A positive result from one or more of these screening tests signals the need for confirmatory karyotyping to clinch the diagnosis. Ultrasound between 11 to 14 weeks of gestation can evaluate nuchal translucency (NT) to screen for Down syndrome. During the second trimester, a triple or quadruple test can also be performed alone or in addition to NT to quantify Down syndrome risk. In limited resource settings however, only the measurement of NT via ultrasound can be performed since biomarker tests are either unavailable or inaccessible. While the diagnostic performance of NT measurement alone has been investigated in several observational studies, there is no consensus on its performance as a sole test to screen for Down syndrome.

To determine the diagnostic performance of NT during prenatal first-trimester ultrasound as a screening test for Down syndrome.

We performed a systematic search on the PubMed, ProQuest, and Cochrane Library databases for recent systematic reviews and meta-analyses that addressed the objective. The existing reviews found were then independently appraised by the two reviewers with the AMSTAR-2 checklist. To update the existing reviews, a systematic search was done in the same databases to identify additional primary diagnostic studies, which were appraised using the QUADAS-2 tool. Random-effects univariate meta-analysis and summary receiving operator curve (HSROC) analysis for the outcomes were performed using Review Manager version 5.4 and R version 4.2.2, respectively. Subgroup analysis was performed by stratifying the baseline risk of mothers for fetal anomaly as low- or high-risk. Highrisk mothers were defined as women with risk factors such as advanced age, positive serum screen, presence of other ultrasound anomalies, and history of previous fetus with anomaly.

We found 22 cohort studies (n=225,846) of women at low-risk for fetal anomaly. The pooled sensitivity was 67.8% (95% CI: 61.4%-73.6%, I2=70.4%) and specificity was 96.3% (95% CI: 95.5%-96.9%, I2=96.7%). For low-risk women, the overall certainty of evidence was low, due to different modes of verification and heterogeneity not completely explained by variability in baseline risk or cut-points. Seven studies (n=9,197) were on high-risk women. The pooled sensitivity was 62.2% (95% CI: 54.1%-69.7%, I2=38.8%) and specificity was 96.5% (95% CI: 93.6%-98.1%, I2=95.5%). For women at high-risk, the evidence was rated as moderate due to differential verification.

Our analysis showed that NT measured through first-trimester ultrasound is specific for Down syndrome but has low sensitivity. Despite this, it is a useful screening test for Down syndrome in low-resource settings where other strategies may not be available or accessible. Furthermore, interpretation of NT results must take into consideration its limited sensitivity as this may lead to missed cases.

BACKGROUND

Down syndrome or trisomy 21, the most common chromosomal disorder, results from the presence of a third copy of chromosome 21 and manifests as mild to moderate intellectual disability, growth retardation, congenital heart defects, gastrointestinal abnormalities, and characteristic facial features. Several methods have been used to screen for Down syndrome in the prenatal period, such as ultrasound, biomarkers, cell-free DNA testing, and combinations of these tests. A positive result from one or more of these screening tests signals the need for confirmatory karyotyping to clinch the diagnosis. Ultrasound between 11 to 14 weeks of gestation can evaluate nuchal translucency (NT) to screen for Down syndrome. During the second trimester, a triple or quadruple test can also be performed alone or in addition to NT to quantify Down syndrome risk. In limited resource settings however, only the measurement of NT via ultrasound can be performed since biomarker tests are either unavailable or inaccessible. While the diagnostic performance of NT measurement alone has been investigated in several observational studies, there is no consensus on its performance as a sole test to screen for Down syndrome.

To determine the diagnostic performance of NT during prenatal first-trimester ultrasound as a screening test for Down syndrome.

We performed a systematic search on the PubMed, ProQuest, and Cochrane Library databases for recent systematic reviews and meta-analyses that addressed the objective. The existing reviews found were then independently appraised by the two reviewers with the AMSTAR-2 checklist. To update the existing reviews, a systematic search was done in the same databases to identify additional primary diagnostic studies, which were appraised using the QUADAS-2 tool. Random-effects univariate meta-analysis and summary receiving operator curve (HSROC) analysis for the outcomes were performed using Review Manager version 5.4 and R version 4.2.2, respectively. Subgroup analysis was performed by stratifying the baseline risk of mothers for fetal anomaly as low- or high-risk. Highrisk mothers were defined as women with risk factors such as advanced age, positive serum screen, presence of other ultrasound anomalies, and history of previous fetus with anomaly.

We found 22 cohort studies (n=225,846) of women at low-risk for fetal anomaly. The pooled sensitivity was 67.8% (95% CI: 61.4%-73.6%, I2=70.4%) and specificity was 96.3% (95% CI: 95.5%-96.9%, I2=96.7%). For low-risk women, the overall certainty of evidence was low, due to different modes of verification and heterogeneity not completely explained by variability in baseline risk or cut-points. Seven studies (n=9,197) were on high-risk women. The pooled sensitivity was 62.2% (95% CI: 54.1%-69.7%, I2=38.8%) and specificity was 96.5% (95% CI: 93.6%-98.1%, I2=95.5%). For women at high-risk, the evidence was rated as moderate due to differential verification.

Our analysis showed that NT measured through first-trimester ultrasound is specific for Down syndrome but has low sensitivity. Despite this, it is a useful screening test for Down syndrome in low-resource settings where other strategies may not be available or accessible. Furthermore, interpretation of NT results must take into consideration its limited sensitivity as this may lead to missed cases.

Human ; Mass Screening ; Mothers ; Nuchal Translucency Measurement ; Prenatal Diagnosis

OBJECTIVE: To assess the value of chromosomal microarray analysis (CMA) and trio-whole exome sequencing (trio-WES) for fetuses with increased nuchal translucency (NT) thickness. METHODS: Sixty two pregnant women who had visited Urumqi Maternal and Child Care Health Hospital between June 2018 and June 2020 for NT ≥ 3.0 mm at 11 ~ 13⁺⁶ gestational weeks were selected as study subjects. Relevant clinical data were collected. The patients were divided into 3.0 ~ ＜3.5 mm (n = 33) and ≥3.5 mm groups (n = 29). Chromosome karyotyping analysis and chromosomal microarray analysis were carried out. And trio-WES analysis was performed on 15 samples with NT thickening but negative CMA results. The distribution and incidence of chromosomal abnormalities in the two groups were compared by using chi-square test. RESULTS: The median age of the pregnant women was 29 years old (22 ~ 41 years old), the median thickness of NT was 3.4 mm (3.0 ~ 9.1 mm), and the median gestational age at the detection was 13⁺⁴ weeks (11⁺⁵ ~ 13⁺⁶ weeks). Chromosome karyotyping analysis has detected 12 cases of aneuploidies and 1 case of derivative chromosome. The detection rate was 20.97% (13/62). CMA has detected 12 cases of aneuploidies, 1 case of pathogenic CNV and 5 cases of variant of uncertain significance (VUS), with a detection rate of 29.03% (18/62). The aneuploidy rate for the NT ≥ 3.5 mm group was higher than that for the 3.0 ≤ NT < 3.5 mm group [3.03% (1/33) vs. 41.38% (12/29), χ² = 13.698, P < 0.001]. There was no statistically significant difference between the two groups in the detection rate of fetal pathogenic CNV and VUS (χ² = 0.028, P > 0.05). Trio-WES analysis of 15 samples with negative CMA result and no structural abnormality has identified 6 heterozygous variants, including SOS1: c.3542C>T (p.A1181V) and c.3817C>G (p.L1273V), COL2A1: c.436C>T (p.P146S) and c.3700G>A (p.D1234N), LZTR1: c.1496T>C (p.V499A), and BRAF: c.64G>A (p.D22N), respectively. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), all of the variants were rated as VUS. CONCLUSION NT thickening can indicate chromosome abnormality, and CMA and trio-WES may be used for the prenatal diagnosis.
Pregnancy ; Humans ; Female ; Adult ; Infant ; Nuchal Translucency Measurement/methods* ; Prenatal Diagnosis/methods* ; Chromosome Aberrations ; Aneuploidy ; Fetus/diagnostic imaging* ; Ultrasonography, Prenatal ; DNA Copy Number Variations ; Transcription Factors

OBJECTIVE: To determine the frequency of chromosomal abnormalities and outcome of pregnancy for fetuses with increased nuchal translucency (NT). METHODS: Between July 2014 and February 2018, 247 fetuses with increased NT (>95th centile)were analyzed by chromosome microarray analysis (CMA). The fetuses were divided into ones with isolated increased NT (168 cases), increased NT with cystic hygroma (20 cases), increased NT with edema (12 cases) or increased NT with other abnormalities (47 cases). All couples were followed up by telephone calls. RESULTS: The rate of chromosomal abnormalities was 31.6% (78/247), which included 66 cases with chromosomal aneuploidies and 12 with copy number variants (CNVs). CNVs accounted for 31.4% (11/35) of total abnormalities among fetuses with isolated increased NT, whilst only 2.3% (1/43) of the total abnormalities among fetuses with non-isolated increased NT. Three fetuses with a normal CMA result had mental and physical retardation. Two of them were diagnosed with single gene disorders by whole exome sequencing. CONCLUSION CMA can detect more chromosomal microdeletion/microduplications among fetuses with isolated increased NT. Furthermore, fetuses with increased NT and anegative CMA result during pregnancy cannot exclude all adverse outcomes.
Aneuploidy ; Chromosome Aberrations ; Chromosomes ; DNA Copy Number Variations ; Edema ; Female ; Fetus ; Humans ; Lymphangioma, Cystic ; Microarray Analysis ; Nuchal Translucency Measurement ; Pregnancy ; Pregnancy Outcome ; Prenatal Diagnosis ; Ultrasonography, Prenatal

OBJECTIVE: To explore the correlation between fetal nuchal fold (NF) thickening and fetal chromosomal abnormality. METHODS: In total 919 pregnant women undergoing ultrasound examination were selected for interventional prenatal diagnosis in order to detect fetal chromosomal abnormality. RESULTS: The detection rate of chromosomal abnormality has significantly increased with NF thickness, advanced maternal age, presence of other ultrasound abnormalities (P<0.05). Trisomy 21 was the most common abnormality, and there was a prepondance for male fetuses. CONCLUSION Increased NF thickness is strongly associated with the risk of fetal chromosomal abnormalities, advanced maternal age and presence of additional ultrasound abnormalities.
Chromosome Aberrations ; Female ; Fetus ; Humans ; Maternal Age ; Nuchal Translucency Measurement ; Pregnancy ; Ultrasonography, Prenatal

OBJECTIVE: To analyze the prognosis of fetuses with cystic hygroma (CH) or nuchal translucency (NT) or nuchal fold (NF) thickening detected by prenatal echography. METHODS: From January 2014 to December 2015, 124 fetuses with CH and NT/NF thickening on prenatal echography were enrolled from Women's Hospital of Zhejiang University School of Medicine. The basic clinical information, ultrasonic results, pregnancy outcomes and newborn follow-ups were analyzed. The cases were grouped by prognosis and the factors affecting prognosis were analyzed with logistic regression. RESULTS: There were 85 cases of labor induction including one stillbirth and 39 cases delivered. Except one infant who died after birth, all live births survived with good prognosis. Univariate analysis showed that the gestational age at diagnosis of poor prognosis group was earlier than that of good prognosis group (<0.01); and the former group also had higher hydrops fetalis rate and additional structural anomalies rate (all <0.01). Multivariate regression analysis showed that hydrops fetalis (=90.105, <0.05) and additional structural anomalies (=61.854, <0.05) were risk factors of poor prognosis in fetuses with CH and NT/NF thickening. CONCLUSIONS Fetuses with diagnosed CH or NT/NF thickening on prenatal ultrasonography are likely to be associated with chromosomal abnormality. Early gestational weeks, hydrops fetalis and additional structural anomalies may indicate poor prognosis.
Female ; Fetus ; Humans ; Hydrops Fetalis ; etiology ; Infant, Newborn ; Lymphangioma, Cystic ; complications ; diagnosis ; Nuchal Translucency Measurement ; Pregnancy ; Pregnancy Outcome ; Prognosis ; Ultrasonography, Prenatal

PURPOSE: This study aimed to evaluate the clinical usefulness of non-invasive prenatal testing (NIPT) as an alternative testing of invasive diagnostic testing in pregnancies with ultrasound abnormalities. MATERIALS AND METHODS: This was a retrospective study of pregnant women with abnormal ultrasound findings before 24 weeks of gestation between April 2016 and March 2017. Abnormal ultrasound findings included isolated increased nuchal translucency, structural anomalies, and soft markers. The NIPT or diagnostic test was conducted and NIPT detected trisomy 21 (T21), T18, T13 and sex chromosomal abnormalities. We analyzed the false positive and residual risks of NIPT based on the ultrasound findings. RESULTS: During the study period, 824 pregnant women had abnormal ultrasound findings. Among the study population, 139 patients (16.9%) underwent NIPT. When NIPT was solely performed in the patients with abnormal ultrasound findings, overall false positive risk was 2.2% and this study found residual risks of NIPT. However, the discordant results of NIPT differed according to the type of abnormal ultrasound findings. Discordant results were significant in the group with structural anomalies with 4.4% false positive rate. However, no discordant results were found in the group with single soft markers. CONCLUSION: This study found different efficacy of NIPT according to the ultrasound findings. The results emphasize the importance of individualized counseling for prenatal screening or diagnostic test based on the type of abnormal ultrasound.
Chromosome Aberrations ; Congenital Abnormalities ; Counseling ; Diagnostic Tests, Routine ; Down Syndrome ; Female ; Humans ; Nuchal Translucency Measurement ; Pregnancy* ; Pregnant Women ; Prenatal Diagnosis ; Retrospective Studies ; Ultrasonography*

Nuchal translucency is an important indicator of an aneuploid fetus in prenatal diagnostics. Previously, only the presence of aneuploid could be confirmed by conventional karyotyping of fetuses with thick nuchal translucency. With the development of genetic diagnostic techniques, however, it has been reported that subtle variations not detectable by conventional karyotyping might occur in cases of pathologic clinical syndrome in euploid fetuses. One of the newer, high-resolution genetic methods in the prenatal setting is chromosomal microarray. The possible association between nuchal translucency thickness with normal karyotype and submicroscopic chromosomal abnormalities detectable by microarray has been studied. How and when to apply microarray in clinical practice, however, is still debated. This article reviews the current studies on the clinical application of microarray in cases of increased nuchal translucency with normal karyotype for prenatal diagnosis.
Aneuploidy ; Chromosome Aberrations ; Comparative Genomic Hybridization ; Fetus* ; Karyotype ; Karyotyping ; Microarray Analysis* ; Nuchal Translucency Measurement* ; Prenatal Diagnosis

PURPOSE: The aim of this study was to assess the diagnostic efficacy of noninvasive prenatal screening for trisomy 18 by assessing the levels of unmethylated-maspin (U-maspin) and fetal nuchal translucency (NT) thickness during the first trimester of pregnancy. MATERIALS AND METHODS: A nested case-control study was conducted using maternal plasma samples collected from 65 pregnant women carrying 11 fetuses with trisomy 18 and 54 normal fetuses. We compared the U-maspin levels, NT thicknesses, or a combination of both in the first trimester between the case and control groups. RESULTS: U-maspin levels and NT thickness were significantly elevated in the first trimester in pregnant women carrying fetuses with trisomy 18 when compared to those carrying normal fetuses (27.2 vs. 6.6 copies/mL, P<0.001 for U-maspin; 5.9 vs. 2.0mm, P<0.001 for NT). The sensitivities of the U-maspin levels and NT thickness in prenatal screening for fetal trisomy 18 were 90.9% and 90.9%, respectively, with a specificity of 98.1%. The combined U-maspin levels and NT thickness had a sensitivity of 100% in prenatal screening for fetal trisomy 18, with a specificity of 98.1%. CONCLUSION: A combination of U-maspin levels and NT thickness is highly efficacious for noninvasive prenatal screening of fetal trisomy 18 in the first trimester of pregnancy.
Case-Control Studies ; Epigenomics* ; Female ; Fetus ; Humans ; Mass Screening* ; Nuchal Translucency Measurement* ; Plasma ; Pregnancy ; Pregnancy Trimester, First* ; Pregnant Women ; Prenatal Diagnosis ; Sensitivity and Specificity ; Trisomy*