Early pregnancy screening for fetal aneuploidy with serum markers and nuchal translucency.

We determined the aneuploidy detection rate achievable by early pregnancy screening with pregnancy associated plasma protein (PAPP)-A, free beta human chorionic gonadotrophin (hCG) and ultrasound nuchal translucency (NT) measurement. Women having prenatal diagnosis were scanned, and a blood sample was taken and stored. Stored samples were tested and a total of 37 were found to have Down syndrome, 8 to have Edwards syndrome and 255 were controls. Results were expressed in multiples of the gestation-specific median (MOM) value in the controls after regression and, for the serum markers, maternal weight adjustment. In Down syndrome the medians were for PAPP-A 0.63 MOM (95 per cent confidence interval (CI) 0.45-0.87); free beta-hCG 1.88 MOM (1.33-2.66); and NT 2.34 MOM (1.70-3.22). Using these parameters the expected detection rate for a 5 per cent false-positive rate for different marker combinations were: 55.3 per cent for PAPP-A and free beta-hCG; 68.4 per cent for NT alone; and 84.6 per cent for PAPP-A, free beta-hCG and NT. The median values for Edwards syndrome were: 0.17 MOM for PAPP-A; 0.18 MOM for free beta-hCG; and 2.64 MOM for NT. Early pregnancy screening with the combined measurement of maternal serum PAPP-A and free beta-hCG and fetal nuchal translucency could achieve a high Down syndrome detection rate.     

Accuracy of Down syndrome risks produced in a first-trimester screening programme incorporating fetal nuchal translucency thickness and maternal serum biochemistry

Over the past three years approximately 12 000 women have been screened in the first trimester through our OSCAR programme, which utilizes fetal NT and maternal serum free beta-hCG and PAPP-A. During this time 30 cases of Down syndrome were identified either prenatally or postnatally. Using an established procedure the accuracy of predicted risk for Down syndrome was assessed in a population of 30 cases of Down syndrome and 11 758 unaffected pregnancies. The correlation between predicted risk and prevalence of Down syndrome was very high (r=0.9995). It is concluded that risks produced by the Fetal Medicine Foundation combined risk algorithm agree very closely with Down syndrome prevalence and can be used with confidence when counselling women of their risk.     

Abnormal first-trimester fetal nuchal translucency and Cornelia De Lange syndrome

BACKGROUND:Cornelia de Lange syndrome is a genetic disorder associated with delayed growth and characteristic facial features. There is no definitive biochemical or chromosomal marker for the prenatal diagnosis of this syndrome. We describe a case of Cornelia de Lange syndrome associated with an increased nuchal translucency in the first trimester.CASE:A large nuchal translucency was identified in a fetus during a first trimester ultrasound. Subsequent second- and third-trimester sonograms demonstrated severe fetal growth restriction, limb shortening, and abnormal facial features, despite normal fetal karyotype per chorionic villus sampling. Neonatal evaluation confirmed the diagnosis of Cornelia de Lange syndrome.CONCLUSION:Sonographic finding of an increased nuchal translucency in early pregnancy is associated with fetal aneuploidy and various structural and genetic abnormalities. Increased nuchal translucency may identify fetuses that require vigilant assessment, especially when found in association with other abnormalities.     

Fetal nuchal translucency and skinfold to screen for fetal aneuploidy

Nuchal translucency (NT) is defined as the accumulation of subcutaneous fluid in the nuchal region of the fetus at 11-14 weeks. Its measurement in order to modify the previous background risk has been proved to be able to detect around 70% of trisomy 21 pregnancies (for a 5% fixed positive rate). When affected fetuses dying before 20 weeks are excluded, detection rate may decrease to 60%. Given that appropriate training of sonographers and adherence to a standard technique for the measurement of NT is of paramount importance to reduce variability, the Fetal Medicine Foundation has established a certification process. Fetal nuchal edema displayed at 15-20 weeks was described as enlarged nuchal skinfold, and is a less sensitive but more specific marker than nuchal translucency. Webbing of the neck in infants with trisomy 21 may be envisaged as the remainder of nuchal distension.     

妊娠早期胎儿颈部透明层厚度与胎儿预后的前瞻性队列研究

目的探讨妊娠早期胎儿颈部透明层(NT)厚度与胎儿预后的关系。方法收集2015年12月至2018年12月于南京大学医学院附属鼓楼医院行妊娠早期胎儿NT厚度测量的单胎孕妇,共4958例建立前瞻性研究队列,进行妊娠早期胎儿结构超声筛查、妊娠早期血清学筛查、妊娠中期超声筛查及对新生儿出生后28 d的体格检查。根据妊娠早期超声筛查的结果,分为胎儿NT增厚(≥3.0 mm)者167例与NT厚度正常者4791例;将胎儿NT增厚的孕妇,分为胎儿单纯NT增厚者86例与NT增厚合并结构异常者81例。分析不同NT厚度胎儿的预后,并重点对单纯NT增厚与NT增厚合并结构异常胎儿的妊娠结局进行分析。妊娠早期超声筛查发现胎儿结构异常或血清学筛查结果为高风险的孕妇,经绒毛穿刺取样术行染色体微阵列分析(CMA)检测以明确产前诊断。结果(1)胎儿NT厚度正常孕妇的妊娠结局:共4791例孕妇,包括胎儿NT厚度正常且无结构异常者4726例,其中妊娠中期及产后新诊断结构异常83例,4688例活产;胎儿NT厚度正常但结构异常的孕妇65例,其中61例孕妇终止妊娠,4例活产。(2)胎儿单纯NT增厚孕妇的妊娠结局:86例孕妇中,66例(76.7%,66/86)行CMA检测,3例胎儿诊断为21三体综合征;除7例孕妇选择终止妊娠外,余79例行妊娠中期超声检查、新生儿出生后28 d体格检查、新生儿电话随访至6~21个月均未发现发育异常。(3)胎儿NT增厚合并结构异常孕妇的妊娠结局:81例孕妇中,73例(90.1%,73/81)行CMA检测,其中32例的胎儿为染色体非整倍体异常。70例选择终止妊娠,2例妊娠中期自然流产,9例活产。(4)NT增厚是否合并结构异常胎儿的产前诊断结果及预后比较:单纯NT增厚的胎儿染色体非整倍体的发生率为3.5%(3/86),合并结构异常者为39.5%(32/81),两者比较,差异有统计学意义(χ2=32.7,P<0.01);胎儿单纯NT增厚孕妇的健康新生儿存活率为91.9%(79/86),合并结构异常者为9.9%(8/81),两者比较,差异有统计学意义(χ2=112.3,P<0.01)。结论妊娠早期,超声筛查胎儿NT及结构,能提高出生缺陷的产前筛查率。单纯NT增厚胎儿的染色体非整倍体的发生率较低,新生儿健康存活率较高。     

The influence of image magnification in first-trimester screening for Down syndrome by fetal nuchal translucency in Asians

OBJECTIVE: The aim of this prospective study was to evaluate the impact of image magnification in the measurements of crown-rump length (CRL) and nuchal translucency (NT) thickness for first-trimester Down syndrome screening in Asians. METHODS: Ultrasound measurements of NT and CRL were performed in 561 consecutive Taiwanese unaffected fetuses and 11 cases of Down syndrome fetuses between 12 and 14 weeks of gestation. All sonographic images were measured by one qualified examiner to prospectively undergo first-trimester NT screening for Down syndrome. Fetal CRL and NT thickness were measured on three separated images including the original image, regular image, and the magnified image. RESULTS: A significant mean difference (0.59 +/- 4.24 mm) of CRL was found between measurements on the original and regular image (p < 0.001). There was a significant mean difference of NT thickness measurements between the regular and magnified image (0.12 +/- 0.25 mm, p < 0.001). Seven out of the 11 cases (63.6%) of Down syndrome with NT thickness > or =2.5 mm was measured on three separated images. A significantly reduced incidence of NT thickness > or =2.5 mm on the magnified image was noted than those of the original and regular image measurements in unaffected cases (p < 0.001). Either using the assessing method by the 95th centile cutoff value of NT thickness or combined risk, our results could achieve observed detection rate of 63.6% measured on three separated images. CONCLUSIONS: Our data indicate that the image magnification could reduce the false-positive rate by using a fixed cutoff value of NT thickness, but would have no influence on the results when using the assessing method either by the 95th centile cutoff value of NT thickness or the combined risk. In order to place the caliper more accurately, a magnified image should be recommended as a standard image in the measurements of the NT thickness.     

If nuchal translucency screening is combined with first-trimester serum screening the need for fetal karyotyping decreases

BACKGROUND: This case-control study was performed to evaluate whether adding first-trimester maternal serum testing to nuchal translucency measurement would improve the antenatal detection of Down's syndrome and decrease the number of women offered fetal karyotyping. METHODS: In the Swedish Nuchal Translucency Trial (the NUPP trial), 39,572 pregnant women were randomized to a routine scan at 12-14 gestational weeks including nuchal translucency screening for Down's syndrome, or a routine scan at 16-18 gestational weeks. From the early scan group 47 pregnancies with Down's syndrome were identified and for each case three controls were chosen. Of the 189 women asked to participate, 31 cases and 108 controls with a singleton pregnancy and frozen serum from 8-14 gestational weeks available for analysis accepted participation. Maternal sera were analyzed for free beta human chorionic gonadotrophin and pregnancy-associated plasma protein A. The risk for Down's syndrome was calculated using combinations of maternal age, crown-rump length, nuchal translucency, and biochemistry. A risk > or =1/250 was considered increased and an indication for fetal karyotyping. RESULTS: Risk calculated on the basis of maternal age alone would have identified 21 of the 31 Down's syndrome cases by karyotyping 61 of the 139 fetuses. Maternal age and nuchal translucency would have identified 29 cases by karyotyping 51 fetuses. Maternal age, nuchal translucency, and biochemistry would also have identified 29 cases by karyotyping 37 fetuses. CONCLUSIONS: By adding first trimester biochemistry to nuchal translucency measurement the detection rate of fetuses with Down's syndrome seems to remain unchanged whereas the antenatal risk group to be offered fetal karyotyping decreases.     

Combined measurement of fetal nuchal translucency, maternal serum free beta-hCG, and pregnancy-associated plasma protein A for first-trimester Down's syndrome screening.

PURPOSE: It has been proposed that first-trimester Down's syndrome screening has a higher detection rate compared to second-trimester biochemical screening. This study investigated the accuracy of Down's syndrome screening during gestational weeks 10 to 13 using the combination of fetal nuchal translucency (NT) measurement with maternal serum concentrations of free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A). METHODS: A total of 1,514 women with singleton pregnancies were enrolled in this study. Fetal NT was measured using the criteria published by the Fetal Medicine Foundation. Maternal serum concentrations of free beta-hCG and PAPP-A were determined by microtiter-plate ELISA. Down's syndrome risk was calculated using multivariate Gaussian distribution and Alpha software. RESULTS: Seventeen (1.12%) of the 1514 screened pregnancies had a fetal NT of at least 3 mm, and 41.2% of these had a poor pregnancy outcome, including four fetal aneuploidies. The odds of a fetal aneuploidy when the NT was greater than 2.0 multiples of median (MoM) was 90, when serum PAPP-A concentration was less than 0.45 MoM, it was 8.6, and when serum free beta-hCG concentration was greater than 2.2 MoM, it was 4.7. Using a risk cut-off level of 1 in 400, nine of 10 fetal aneuploidies were identified with a 4.7% false-positive rate, including two with trisomy 21, one with trisomy 18, and three with Turner's syndrome. CONCLUSIONS: This study demonstrated that Down's syndrome screening using the combined test in the first trimester had a higher detection rate than that of serum screening in the second trimester. Implementation of NT measurement in the first trimester provides substantial advantages for Down's syndrome detection and early diagnosis of fetal structural abnormalities.     

Relation between increased fetal nuchal translucency thickness and chromosomal defects

OBJECTIVE: To examine the prevalence and distribution of all chromosomal defects in fetuses with increased nuchal translucency thickness. METHODS: Assessment of risk for trisomy 21 was carried out by a combination of maternal age and fetal nuchal translucency thickness at 11-13 + 6 weeks. A search of the database was made to identify, first, all singleton pregnancies in which fetal karyotyping was carried out and, second, the cases where the fetal nuchal translucency was equal to or above the 95th centile for fetal crown-rump length. The prevalence and distribution of chromosomal defects were determined for each nuchal translucency category: between the 95th centile for crown-rump length and 3.4 mm, 3.5-4.4 mm, 4.5-5.4 mm, 5.5-6.4 mm, 6.5-7.4 mm, 7.5-8.4 mm, 8.5-9.4 mm, 9.5-10.4 mm, 10.5-11.4 mm, and 11.5 mm or more. RESULTS: The search identified 11,315 pregnancies. The median maternal age was 34.5 (range 15-50) years, and the median fetal crown-rump length was 64 (range 45-84) mm. The fetal karyotype was abnormal in 2,168 (19.2%) pregnancies, and the incidence of chromosomal defects increased with nuchal translucency thickness from approximately 7% for those with nuchal translucency between the 95th centile for crown-rump length and 3.4 mm to 75% for nuchal translucency of 8.5 mm or more. In the majority of fetuses with trisomy 21, the nuchal translucency thickness was less then 4.5 mm, whereas in the majority of fetuses with trisomies 13 or 18 it was 4.5-8.4 mm, and in those with Turner syndrome it was 8.5 mm or more. CONCLUSION: In fetuses with increased nuchal translucency, approximately one half of the chromosomally abnormal group is affected by defects other than trisomy 21. The distribution of nuchal translucency is different for each type of chromosomal defect. LEVEL OF EVIDENCE: II-3.     

First-trimester screening for Down syndrome in France combining fetal nuchal translucency measurement and biochemical markers

BACKGROUND: In France, there is a strictly regulated National Screening Programme for Down syndrome, based on second-trimester maternal serum markers. A prospective study of nuchal translucency together with retrospective evaluation of maternal serum markers was carried out to inform decisions on whether to move the programme to the first trimester. METHODS: Between January 1998 and June 2001, all women who presented for their prenatal care at 12 participating maternity units were, regardless of age, invited to provide a blood sample and to attend for an NT scan at 11 to 13 weeks. The results were used to derive Gaussian distribution parameters. Detection and false-positive rates were computed in two ways: statistical modelling and directly. The cut-off risk was 1 in 250 at term. RESULTS: A total of 5694 women with singleton pregnancies were screened including 26 with Down syndrome and 24 with other aneuploidies. The model-predicted detection and false-positive rates for combined ultrasound and serum screening were 81 and 4.5% compared to 64 and 6.0% for ultrasound alone. The directly observed rates were 73 and 4.7%, compared to 62 and 5.0% respectively. CONCLUSION: In France, first-trimester screening with nuchal translucency and maternal serum markers is likely to achieve a high screening efficiency. This has important implications for the national screening policy.     

Comparison and integration of first trimester fetal nuchal translucency and second trimester maternal serum screening for fetal Down syndrome

BACKGROUND: It is uncertain whether first trimester nuchal translucency (NT) is more effective than the well-established second trimester serum screening for fetal Down syndrome or whether their combination works best. We report data from a large multicentre non-interventional trial in which all subjects underwent both first and second trimester screening. METHODS: All women who attended the obstetric clinic before 15 weeks' gestation were recruited. An ultrasound examination was performed at 10 to 14 weeks to measure the NT. The nuchal measurements were not acted upon unless the fetus showed gross features of hydrops fetalis. All women had serum alpha-fetoprotein (AFP) and human chorionic gonadotrophin (hCG) assay at 15 to 20 weeks. The Down syndrome risk assigned by serum screening was disclosed and amniocentesis was offered if this assigned risk was >or=1:250 or if the women were 35 years and older. The efficacy of different combinations of screening markers was compared. RESULTS: Between January 1997 and August 2000, 17 590 women were recruited (19% >or=35 years old). After excluding subjects who miscarried, defaulted the serum test and other reasons, 16 237 pregnancies were analysed. Of these, 35 pregnancies were affected by Down syndrome (2.2 cases per 1000 pregnancies). At a false-positive rate of 5%, the detection rate of Down syndrome by NT alone, NT and age, serum hCG, AFP and age, and NT, hCG, AFP and age were 61%, 69%, 73% and 86%, respectively. CONCLUSION: Integration of NT and second trimester serum AFP and hCG assay yielded the best screening efficacy for Down syndrome.     

A first trimester trisomy 13/trisomy 18 risk algorithm combining fetal nuchal translucency thickness,maternal serum free beta-hCG and PAPP-A

This study examines 45 cases of trisomy 13 and 59 cases of trisomy 18 and reports an algorithm to identify pregnancies with a fetus affected by trisomy 13 or 18 by a combination of maternal age fetal nuchal translucency (NT) thickness, and maternal serum free beta-hCG and PAPP-A at 11-14 weeks of gestation. In this mixed trisomy group the median MoM NT was increased at 2.819, whilst the median MoMs for free beta-hCG and PAPP-A were reduced at 0.375 and 0.201 respectively. We predict that with the use of the combined trisomy 13 and 18 algorithm and a risk cut-off of 1 in 150 will for a 0.3% false positive rate allow 95% of these chromosomal defects to be identified at 11-14 weeks. Such algorithms will enhance existing first trimester screening algorithms for trisomy 21.