Increased nuchal translucency in trisomy 13 fetuses at 10–14 weeks of gestation

In a multicenter screening study for trisomy 21 involving ultrasonographic measurement of fetal nuchal translucency thickness (NT) at 10–14 weeks of gestation, 100,311 singleton pregnancies with a live fetus were examined. There were 46 cases of trisomy 13, and in 33 (72%) of these, the NT was above the 95th centile. The estimated risk for trisomy 21, based on maternal age-related risk for this chromosomal abnormality and fetal NT, was above 1 in 300 in 37 (80.1%) of the trisomy 13 fetuses. The fetal crown-rump length was significantly reduced, but the fetal heart rate was increased, being above the 95th centile in 64% of cases. Additionally, 24% of trisomy 13 fetuses had holoprosencephaly and 10% had exomphalos. This study has demonstrated that at 10–14 weeks of gestation, about 80% of fetuses with trisomy 13 can be identified in a screening program for trisomy 21, based on a combination of maternal age and fetal NT. Am. J. Med. Genet. 86:205–207, 1999. © 1999 Wiley-Liss, Inc.     

胎儿颈部半透明膜厚度测定筛查胎儿染色体异常

目的探讨孕早期筛查胎儿染色体异常的方案.方法 2241例孕龄在11～14w单胎妊娠的孕妇接受筛查.采用腹式或阴式B型超声波测量胎儿颈部半透明膜(NT)厚度;根据所测NT数据结合孕妇年龄由计算机算出胎儿染色体异常风险率.对所筛查出的高风险胎儿则进一步进行产前诊断(羊水细胞染色体核型分析).结果共筛查出26例染色体异常,包括Down综合征16例(61.54%)、性染色体数目异常6例(23.08%)、染色体结构异常4例(15.38%).所有接受筛查的孕妇中风险大于1/250者344例(15.35%);染色体异常检出率为80.77%,假阳性率为6.50%;21三体检出率为87.50%.结论孕早期NT 孕妇年龄二联筛查方案对孕早期临床筛查胎儿染色体异常有较好的实用价值.     

Abnormalities of the heart and great arteries in first trimester chromosomally abnormal fetuses

Pathological examination of the heart and great arteries was performed in 112 chromosomally abnormal fetuses after surgical termination of pregnancy at 11–16 weeks of gestation. The chromosomal abnormalities were diagnosed by chorion villus sampling which was carried out because screening of the pregnancies by a combination of maternal age and fetal nuchal translucency thickness at 10–14 weeks of gestation identified them as being at increased risk. The group consisted of 60 fetuses with trisomy 21, 29 with trisomy 18, 17 with trisomy 13 and 6 with Ullrich-Turner syndrome. The most common cardiac lesion seen in trisomy 21 fetuses was an atrioventricular or ventricular septal defect. Trisomy 18 was associated with ventricular septal defects and/or polyvalvular abnormalities. In trisomy 13, there were atrioventricular or ventricular septal defects, valvular abnormalities, and either narrowing of the isthmus or truncus arteriosus. Ullrich-Turner syndrome was associated with severe narrowing of the whole aortic arch. In all four groups of chromosomally abnormal fetuses, the aortic isthmus was significantly narrower than in normal fetuses and the degree of narrowing was significantly greater in fetuses with high nuchal translucency thickness. It is postulated that narrowing of the aortic isthmus may be the basis of increased nuchal translucency thickness in all four chromosomal abnormalities. Am. J. Med. Genet. 69:207–216, 1997. © 1997 Wiley-Liss, Inc.     

Early prediction of severe twin-to-twin transfusion syndrome

This extended series of 303 monochorionic twin pregnancies examined at 10-14 weeks gestation explores the possible association of increased fetal nuchal translucency thickness (NT) in the early prediction of severe twin-to-twin transfusion syndrome (TTS). Of 303 pregnancies, there were 16 in which at least one fetus was structurally or chromosomally abnormal and in the remaining 287 ongoing pregnancies there were 43 (15%) which developed severe TTS. The median fetal NT was 1.0 multiples of the median (MOM) and NT was >95th centile in 47 (8.2%) fetuses and in at least one fetus in 37 (12.9%) pregnancies. The prevalence of increased NT in the pregnancies that developed TTS [17.4% (n = 15) of fetuses and 28% (n = 12) of pregnancies] was significantly higher than in the non-TTS group [6.6% (n = 32) and 10.2% (n = 25) respectively; Z: = -3.4, P: < 0.001 and Z: = 3.2, P: < 0.001 respectively], likelihood ratio of increased fetal NT for prediction of TTS = 3.5 [95% confidence interval (CI) 1.9-6.2]. In 153 of the pregnancies, an ultrasound examination was also performed at 15-17 weeks gestation and intertwin membrane folding was seen in 49 (32%) cases; 21 of these (43%) subsequently developed TTS compared to two (1.9%) of the 104 pregnancies without membrane folding (Z: = 6.6, P: < 0.001), likelihood ratio of membrane folding for prediction of TTS = 4.2 (95% CI 3.0-6.0).     

Investigation of maternal blood enriched for fetal cells: role in screening and diagnosis of fetal trisomies.

Prenatal diagnosis of chromosomal abnormalities relies on assessment of risk followed by invasive testing in the group with highest risk. Assessment of risk by a combination of maternal age and fetal nuchal translucency and invasive testing in the 5% of the population with the highest risk would identify about 80% of trisomy 21 pregnancies. Preliminary reports suggest that chromosomal abnormalities can also be diagnosed by fluorescent in situ hybridization (FISH) in maternal blood enriched for fetal cells. This study examines the potential role of this method on the prenatal diagnosis of fetal trisomies. Maternal blood was obtained before invasive testing in 230 pregnancies at 10-14 weeks of gestation. After enrichment for fetal cells, by triple density centrifugation and anti-CD71 magnetic cell sorting, FISH was performed and the proportion of cells with positive signals in the chromosomally normal and abnormal groups was determined. Fetal karyotype was normal in 150 cases and abnormal in 80 cases, including 36 with trisomy 21. Using a 21 chromosome-specific probe, three-signal nuclei were present in at least 5% of the enriched cells from 61% of the trisomy 21 pregnancies and in none of the normal pregnancies. For a cut-off of 3% of three-signal nuclei the sensitivity for trisomy 21 was 97% for a false positive rate of 13%. Similar values were obtained in trisomies 18 and 13 using the appropriate chromosome-specific probe. Examination of fetal cells from maternal blood may provide a noninvasive prenatal diagnostic test for trisomy 21 with the potential of identifying about 60% of affected pregnancies. Alternatively, this technique can be combined with maternal age and fetal nuchal translucency as a method of selecting the high-risk group for invasive testing. Potentially, 80% of trisomy 21 pregnancies could be identified after invasive testing in less than 1% of the pregnant population.     

Fetal plasma carbonic anhydrase III in prenatal diagnosis of Duchenne muscular dystrophy

Carbonic anhydrase III (CAIII), a skeletal-muscle-specific enzyme which is elevated in the plasma of Duchenne muscular dystrophy (DMD) patients, was measured by radioimmunoassay in fetal plasma in order to evaluate its application to prenatal diagnosis of DMD. Using fetoscopy, pure fetal blood samples were taken at 17-24 weeks gestation from 25 fetuses at risk for DMD and from 78 control fetuses. Care was taken in the handling and storage of all samples. Normal sons were born in eight cases at risk for DMD. The CAIII levels in the infants were not significantly different from those of the control infants. Pregnancies were terminated in the remaining 17 at-risk cases. The CAIII levels in the fetuses were significantly different (p = 0.0034) from those of the control fetuses, although the distributions overlapped. Based on prior maternal risk, seven affected fetuses were expected in the terminated group; five had CAIII levels at or above the 95th centile of the control range. It is suggested that measurement of CAIII achieves partial discrimination between affected fetuses and their normal at-risk brethren.     

First-trimester screening for trisomy 21 in singleton pregnancies achieved by assisted reproduction.

BACKGROUND: The possible effect of assisted reproduction on first-trimester screening for trisomy 21 was examined by fetal nuchal translucency thickness (NT), maternal serum free beta-human chorionic gonadotrophin (HCG) and pregnancy-associated plasma protein-A (PAPP-A). METHODS: Parameters were measured at 11-14 weeks in 411 singleton pregnancies achieved by controlled ovarian stimulation, including 220 that had undergone IVF. Results were compared with 1233 singleton pregnancies conceived spontaneously. RESULTS: In the IVF pregnancies, the median fetal NT was not significantly different from that in controls, whilst the median free beta-HCG was significantly increased, and PAPP-A was significantly decreased. In the intracytoplasmic sperm injection group, fetal NT and free beta-HCG values were not significantly different from those in controls, but PAPP-A was significantly decreased. In those pregnancies achieved by ovarian stimulation, neither fetal NT, free beta-HCG nor PAPP-A were significantly different from the control group. CONCLUSIONS: In IVF pregnancies, screening for trisomy 21 by fetal NT, maternal serum free beta-HCG and PAPP-A levels may be associated with a 1.2% higher false-positive rate than in natural conception.     

Investigation of maternal blood enriched for fetal cells: Role in screening and diagnosis of fetal trisomies

Prenatal diagnosis of chromosomal abnormalities relies on assessment of risk followed by invasive testing in the group with highest risk. Assessment of risk by a combination of maternal age and fetal nuchal translucency and invasive testing in the 5% of the population with the highest risk would identify about 80% of trisomy 21 pregnancies. Preliminary reports suggest that chromosomal abnormalities can also be diagnosed by fluorescent in situ hybridization (FISH) in maternal blood enriched for fetal cells. This study examines the potential role of this method on the prenatal diagnosis of fetal trisomies. Maternal blood was obtained before invasive testing in 230 pregnancies at 10–14 weeks of gestation. After enrichment for fetal cells, by triple density centrifugation and anti-CD71 magnetic cell sorting, FISH was performed and the proportion of cells with positive signals in the chromosomally normal and abnormal groups was determined. Fetal karyotype was normal in 150 cases and abnormal in 80 cases, including 36 with trisomy 21. Using a 21 chromosome-specific probe, three-signal nuclei were present in at least 5% of the enriched cells from 61% of the trisomy 21 pregnancies and in none of the normal pregnancies. For a cut-off of 3% of three-signal nuclei the sensitivity for trisomy 21 was 97% for a false positive rate of 13%. Similar values were obtained in trisomies 18 and 13 using the appropriate chromosome-specific probe. Examination of fetal cells from maternal blood may provide a noninvasive prenatal diagnostic test for trisomy 21 with the potential of identifying about 60% of affected pregnancies. Alternatively, this technique can be combined with maternal age and fetal nuchal translucency as a method of selecting the high-risk group for invasive testing. Potentially, 80% of trisomy 21 pregnancies could be identified after invasive testing in less than 1% of the pregnant population. Am. J. Med. Genet. 85:66–75, 1999. © 1999 Wiley-Liss, Inc.     

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.     

Hyaluronan in the nuchal skin of chromosomally abnormal fetuses

Nuchal skin oedema at 10-14 weeks gestation, observed by ultrasonography as increased nuchal translucency (NT), is found in approximately 70% of fetuses with trisomies 21, 18 and 13 as well as those with Turner's syndrome. This study investigates the possibility that one mechanism for increased translucency is an altered composition of the skin with a higher concentration of hyaluronan; large amounts of hyaluronan can lead to excessive hydration of the extracellular matrix. We isolated the hyaluronic acid binding region (HABR) from aggrecan in the extracellular matrix of hyaline cartilage and used it in a biotinylated form in combination with a fluorescent probe as a marker for hyaluronan. Immunohistochemistry was then used to examine the nuchal skin of chromosomally abnormal and normal fetuses, obtained after termination of pregnancy. In fetuses with trisomy 21 there was a substantial increase in hyaluronan, whereas in trisomies 18 and 13 and Turner's syndrome the amount was similar to that in chromosomally normal controls. This finding suggests that hyaluronan may be implicated in the pathogenesis of increased NT in fetuses with trisomy 21, but the common phenotypic expression of increased translucency in different chromosomal abnormalities may be the consequence of other mechanisms.     

Morphological classification of nuchal skin in human fetuses with trisomy 21, 18, and 13 at 12—18 weeks and in a trisomy 16 mouse

An increase in the nuchal translucency that can be detected at 10–14 weeks of gestation by ultrasound forms the basis for a screening test for chromosomal abnormality. Several mechanisms leading to this increase in skin thickness have been proposed, including changes of the extracellular matrix, cardiac defects and abnormalities of the large vessels. This study examines the composition of the extracellular matrix of the skin in gestational age-matched fetuses with trisomy 21, 18 and 13 from 12–18 weeks. Immunohistochemistry was applied with monoclonal and polyclonal antibodies against collagen type I, III, IV, V and VI and against laminin and fibronectin. Collagen type VI gene expression was further studied by in situ hybridization to detect differences in expression patterns of COL6A1, COL6A3 and COL1A1 between normal fetuses and those with trisomy 21. The ultrastructure of tissue samples was studied by transmission electron microscopy (TEM) and additionally by immunogold TEM. Further, we examined the morphology of the skin in an animal model for Down’s syndrome, the murine trisomy 16, by light and TEM. The dermis of trisomy 21 fetuses was richer in collagen type VI than that of normal fetuses and other trisomies, and COL6A1, located on chromosome 21, was expressed in a wider area than COL6A3, which is located on chromosome 2. Collagen type I was less abundant in the skin of trisomy 18 fetuses, while the skin of all three trisomies contained a dense network of collagen type III and V in comparison with normal fetuses. Collagen type IV, of which two genes are located on chromosome 13, was expressed in the basement membranes of the skin in all fetuses and additionally in the dermal fibroblasts only of trisomy 13 fetuses. Likewise, laminin was present in all basement membranes of normal and trisomic fetuses as well as in dermal fibroblasts of fetuses with trisomy 18. LAMA1 and LAMA3 genes are located on chromosome 18. Dermal cysts were found in the skin of trisomy 18 and 13, but not in trisomy 21 and normal fetuses. Ultrastructural findings showed that an extracellular precipitate containing glycosaminoglycans was regularly present in the skin of trisomy 21 fetuses and murine trisomy 16 embryos. In conclusion, this study suggests that the skin edema in fetal trisomies is characterized by specific alterations of the extracellular matrix that may be attributed to gene dosage effects as a result of a genetic imbalance due to the condition of fetal trisomy.     

Performance of prenatal screening by non-invasive cell-free fetal DNA testing for women with various indicationsCSCD

Objective: To assess the performance of non-invasive prenatal testing (NIPT) based on massive parallel sequencing. Methods: A total of 10 275 maternal blood samples were collected. Fetal chromosomal aneuploides were subjected to low coverage whole genome sequencing. Patients with high risks received further prenatal diagnosis. The outcome of all patients were followed up. Results: High-throughput sequencing detected 72 pregnancies with fetal autosomal chromosomal aneuploidy, including 57 cases of trisomy 21, 14 cases of trisomy 18, and 1 case of trisomy 13. The positive predictive value for trisomies 21 and 18 were 98.25% and 91.67%, respectively. Comparing its performance in intermediate or high risk pregnancies, advanced maternal age pregnancies and volunteering to test pregnancies, the positive predictive value were 100%, 95%, 90% and 50%, respectively. The follow up result was only 1 case of 21 trisomy false negative with high risk. For the 56 cases of trisomy 21, the high risk group accounted for 55%, advanced maternal age accounted for 29%, the intermediate risk referred to 14%, the volunteering to test group accounted for 2%. Conclusion: The performance of NIPT for trisomies 21, 18 and 13 was satisfactory. The method can be used for women with advanced gestational age. NIPT has offered an ideal secondary screening method for those with an intermediate or high risk, and can reduce the rate of birth defects. © 2018 West China University of Medical Sciences. All rights reserved.     

The feasibility of nuchal translucency measurement in higher order multiple gestations achieved by assisted reproduction.

Nuchal translucency (NT) measurement for screening chromosomal abnormalities and detecting fetal anomalies is an effective ultrasonographic marker, originally developed for singleton pregnancies. This study sought to evaluate the feasibility of NT measurements in higher order multiple gestations. Pregnant patients who conceived following assisted reproduction and were carrying three or more fetuses were enrolled in the study. Each fetus was ultrasonographically assessed, a NT measurement was obtained, and the findings were used for counselling prior to any invasive procedure. In all, 24 pregnant patients, initially carrying 79 fetuses aged 10-14 weeks of gestation, were compared with 79 consecutively matched, singleton controls, naturally conceived, having similar crown-rump lengths (+/- 3 mm). NT measurements were feasible for both study and control fetuses, which exhibited similar NT measurements for 5th, 50th and 95th centiles. Also, mean NT thicknesses [measurements in mm or multiple of the medians (MOM)] were similar for both groups (1.41 +/- 0.41 and 1.35 +/- 0.39 mm respectively and 0.87 +/- 0.23 and 0.83 +/- 0.25 MOM respectively). Prenatally no chromosomal abnormalities were detected in either group, and, of those infants who had no karyotyping, no traits were observed that warranted chromosomal analysis. NT measurements are feasible in higher order multiple gestations. Since there is no other effective screening modality for these pregnancies, it seems reasonable to recommend NT measurement for antenatal screening services for higher order multiple gestations.     

Aneuploidy screening in the first trimester

This article reviews the performance of first trimester screening for chromosomal anomalies using various combinations of ultrasound and maternal serum biochemical modalities. Detection rates in excess of 90% can be routinely achieved for Trisomy 21, Trisomy 13, Trisomy 18 using a combination of fetal nuchal translucency (NT) thickness and maternal serum free ss-hCG and PAPP-A at 11 + 0 to 13 + 6 weeks of gestation.     

Triple marker screening for fetal chromosomal abnormalities in Korean women of advanced maternal age

The purpose of this article is to assess the value of maternal serum triple marker screening of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) for the prenatal diagnosis of fetal chromosomal abnormalities in Korean women of advanced maternal age. Maternal sera were collected from 458 pregnant Korean women aged 35 between 15 and 20 weeks gestation before amniocentesis. A patient- specific second trimester risk for fetal Down's syndrome was calculated using the median values for AFP, hCG, uE3 and maternal age. Twelve fetal chromosomal abnormalities were identified. These included six cases of trisomy 21, one case of 46,XY/47,XY,+21, two cases of trisomy 18, one case of trisomy 13, and two cases of 45, X. A cutoff level of 1:200 detected 85.7% (6/7) of the cases of Down's syndrome and 20% (1/5) of the other aneuploidies, with a 27.3% false positive rate. However, a cutoff level of 1:270 did not result in any gains in detecting Down's syndrome or other aneuploidies at the expense of a false positive rate of 34.3%. Second trimester triple marker testing is an effective screening tool for detecting fetal Down's syndrome in Korean women > or = 35 years old. However, it is not an effective screening tool for non-Down's chromosomal abnormalities.     

Down's syndrome screening with nuchal translucency at 12(+0)-14(+0) weeks and maternal serum markers at 14(+1)-17(+0) weeks: a prospective study

BACKGROUND: Sonographic and biochemical methods for Down's syndrome screening have developed simultaneously, but independently. As a consequence, the rate of invasive procedures for fetal karyotyping has dramatically increased and become an important public health issue which needs to be controlled. One approach is to combine sonographic and biochemical results into a single risk assessment. METHODS: In a multicentre interventional study, nuchal translucency (NT) was measured between 12(+0) and 14(+0) weeks of gestation. Maternal serum markers (MSM) were measured between 14(+1) and 17(+0) weeks of gestation. Karyotyping was advised when: (i) NT was > or =3 mm; or (ii) the MSM-related risk was > or =1 in 250 at term. Karyotyping was delayed until after a maternal blood sample had been taken. NT and MSM were expressed as multiples of the medians (MoMs), and risks were calculated and tailored to the study population. A combined risk for NT and MSM was estimated retrospectively. Costs per case diagnosed, and the cost per case averted were calculated for the three screening strategies. RESULTS: A total of 9444 women was screened. Twenty-one fetuses (0.22%) had Down's syndrome, whilst 326 women (3.4%) were lost to follow-up. Among 9118 women followed up, 5506 had both NT and MSM, 821 had only NT, and 2791 had only MSM. Median maternal age was 30.5 years. False-positive rates for NT, MSM and NT combined with MSM were 3.0, 5.8 and 0.23% respectively. The false-positive rate generated by a sequential two-stage screening was 8.6%. Detection rates of Down's syndrome were 62 and 55% for NT and MSM respectively. Seven cases with Down's syndrome (35%) had raised NT and MSM, and 17 (81%) had either raised NT, MSM, or both. For a 5% false-positive rate, detection rates were 55 and 80% for NT alone and for combined NT and MSM respectively. Ultrasound alone appears to be more cost-effective ( pound50 per case diagnosed) than both tests ( pound61 per case diagnosed). CONCLUSIONS: The study results suggest a 25% increase in the detection rate of Down's syndrome using a combination of NT measurement at 12(+0)-14(+0) weeks and MSM at 14(+1)-17(+0) weeks for a 5% false-positive rate, with modest increase in cost.     

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

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

妊娠中晚期羊水细胞胎儿染色体异常核型分析

目的:分析妊娠中、晚期胎儿羊水染色体核型,了解该时期异常核型出现的频率类型及与诊断指征的关系。方法:357例有产前诊断指征的孕妇,在妊娠13-17行羊膜腔穿刺术,取羊水细胞培养,分析胎儿染色体核型。结果:羊水细胞培养成功率91.6%,发现异常核型21例(6.4%),其中妊娠中期检出异常5.7%(16/282);晚期异常11.1%(5/45),P>0.05。染色体异常携带者和各种三体为主要的异常核型,分别占52.4%(11/21)和33.3%(7/21)。高龄孕妇异常检出率为10.2%(5/49),非高龄组为5.8%(16/278),P>0.05。平衡易位组为52.4%,(11/21);胎儿宫内发育迟缓(IUGR)16.7%(1/6)血清学筛查风险值增高为5.9%(1/17)。结论:在有产前诊断为指征的孕妇,胎儿染色体异率为6.4%,染色体异常携带者和各种三体为主要的异常,是高龄以及IUGR最常见的异常。羊水细胞培养对于中、晚期妊娠的高风险孕妇行产前诊断是安全、可靠、诊断方法之一。     

胎儿染色体非整倍体与产前超声特征的对比分析

目的探讨胎儿非整倍体的产前超声特征。方法收集99例曾在孕11周-13^＋6周及孕18周-24周间进行产前超声检查的胎儿非整倍体的核型和超声资料,分析非整倍体超声指标异常的数目和类型。结果99例包括21三体53例,18三体23例,13三体5例,性染色体非整倍体（SCA）16例和其他非整倍体2例。83。8％出现超声指标异常,50．5％出现多项指标异常,33．3％出现单项指标异常,16．2％未出现指标异常,包括21三体7例和SCA8例;21三体常见指标异常有颈项透明层（NT）增厚、鼻骨缺失、室缺、三尖瓣反流;18三体常见指标异常有NT增厚、室缺、双手姿势异常;l3三体最常见畸形为全前脑;SCA常见指标异常有颈部水囊瘤、NT增厚。结论单项超声指标异常也不排除胎儿非整倍体,部分21三体及SCA产前超声指标未见异常,各非整倍体的异常超声指标分布及特征性超声指标有所不同。     

The risk of fetal loss following a prenatal diagnosis of trisomy 13 or trisomy 18

The objective of this study is to determine the risk of fetal loss (spontaneous abortion or stillbirth) following a prenatal diagnosis of trisomy 13 (T13; Patau syndrome) or trisomy 18 (T18; Edwards syndrome). Five regional congenital anomaly registers in England and Wales provided details on the outcomes of 198 pregnancies prenatally diagnosed with T13 and 538 prenatally diagnosed with T18. For each pregnancy the time from prenatal diagnosis until birth, miscarriage or termination occurred was calculated and these times were analyzed using Kaplan-Meier survival functions. Our results showed that between 12 weeks gestation and term an estimated 49% (95% CI: 29-73%) of pregnancies diagnosed with T13 and 72% (61-81%) of pregnancies diagnosed with T18 ended in a miscarriage or stillbirth. Between 18 weeks and term the proportions were 42% (18-72%) for T13 and 65% (57-79%) for T18 and between 24 weeks and term the proportions were 35% (5-70%) for T13 and 59% (49-77%) for T18. Male fetuses with T18 appeared to be more likely to be lost than female fetuses. These are the most precise estimates currently available for the risk of loss in a general population. These estimates should be useful in counseling women who are carrying an affected fetus and knowing the risk of fetal loss is essential to compare the performance of prenatal screening programs occurring in the first and second trimester.