兰州地区孕妇孕中期产前筛查结果回顾性分析

目的通过检测孕妇血清中AFP,Free-βhOG和uE3的浓度,对孕中期胎儿患DS、ES和NTD的风险进行评估。方法运用时间分辨荧光法定量测定孕妇血清中AFP,Free-βhC6和uE,的浓度,采用“Life cycle 3．2”软件计算风险。结果9430例孕妇中高龄共289例,占总筛查人数的3．06％,其中DS、BS和NTD的阳性筛查率分别为5．4％（1／19）、0．21％（1／476）和O．32％（1／313）。确诊阳性病例19例,其中高龄lO例。结论孕中期母血清三联产前筛查是检测胎儿染色体异常的有效途径,对降低出生缺陷,提高人口素质有重要意义。     

Prenatal maternal blood screening for the detection of fetal chromosomal abnormalities: clinical importance of the rate of false positives

Maternal serum screening to identify fetal aneuploidies is now routinely offered during the second trimester of pregnancy in developed countries. The purpose of this prospective study was to assess the value of maternal serum screening between 15 and 20 weeks of gestation to detect fetal aneuploidies and to determine the false positive rate (FPR). Blood samples were collected from 1,062 pregnant women between 15 and 20 weeks of gestation. Samples were assayed for alpha-fetoprotein (AFP), free beta human chorionic gonadotropin (beta-hCG) and unconjugated estriol (uE3). Medians were established at each week from 200 normal, singleton pregnancies. Second trimester risk was calculated using the maternal age and different combinations of AFP, beta-hCG and uE3. Screening results calculated by likelihood ratio to be equal to or greater than 1:270 were considered positive. If the gestational age was confirmed by ultrasonography, genetic counselling and amniocentesis were offered. Ten fetal chromosomal abnormalities were detected with maternal serum screening. Sample's size does not allow a correct detection rate estimation, but false positive rate (FPR) was found to be 6.5%. This FPR has a clinical application. At a cut-off of 1:270, second trimester screening best results were obtained using a combination of all three biochemical markers. These results confirm the efficacy of maternal serum screening for fetal chromosomal abnormalities with a low FPR. The measurement of AFP, beta-hCG and uE3 is an effective prenatal screening test.     

唐氏综合征孕中期多指标联合筛查方案适用性评估

目的 对孕中期多种产前筛查方案进行比较、评价,为选择较为适宜的方案提供依据.方法 收集2009年在青岛市产前诊断中心知情同意接受产前筛查的单活胎妊娠30 547例,分别检测母血清中二联或三联血清标记物,均用Lifecycle软件评估胎儿罹患唐氏综合征的风险,对二者的检出率和成本效益进行比较、分析;同时收集64例唐氏综合征妊娠的血清标本,采用二联筛查(double test,DT)+2T-Risks软件计算风险(DT-2T),二联筛查+Lifecycle软件计算风险(DT-LC),三联筛查(triple test,TT)+2T-Risks软件计算风险(TT-2T)和三联筛查+ Lifecycle软件计算风险(TT-LC)4种不同的筛查方案对胎儿罹患唐氏综合征的风险进行评估,并对各种不同的筛查方案进行比较、评价.结果 (1)64例唐氏综合征妊娠的血清标本,采用Lifecycle软件进行风险评估,检出率均高于同样指标筛查而采用2T-Risks软件评估风险方案;三联筛查不适宜使用2T-Risks软件;(2)30 547例单活胎妊娠的筛查中,DT-LC方案和TT-LC方案对于唐氏综合征的检出率分别为56.25%和57.14%;每检出1例唐氏综合征的平均费用DT-LC方案明显低于TT-LC方案,为优选方案.结论 孕中期DT-LC方案是一种利于在全国广泛开展的、经济有效的筛查方案.

Abstract：

Objective To provide basis for selecting the suitable method of Down's syndrome biochemical screening in the second trimester pregnancy. Methods A total of 30 547 singleton pregnancies between 14 and 20+6 weeks of pregnancy were collected and analyzed for maternal serum alpha-fetoproteins (AFP) and human chorionic gonadotrophin,free beta subunit (β-HCG) with or without unconjugated estriol (uE3). The screening risks were calculated using the software Lifecycle. The detection rates and the cost of per Down's syndrome detected were calculated and compared. And four different methods were compared in a series of 64 serum samples from Down's syndrome pregnancies. Results (1) Among the 64 affected cases, the detection rate of Down's syndrome was improved no matter in the double test (DT) or in the triple test (TT) if software Lifecycle (LC) was used to evaluate risks. And it was not suitable to evaluate risks with software 2T-Risks in the triple tests. (2) In the cohort of 30 547 singleton pregnancies, the detection rate of Down's syndrome with project DT-LC, which was double test using AFP and free β-HCG together with software Lifecycle, and project TT-LC, which was triple test using AFP, free β-HCG and uE3 together with software Lifecycle, was 56.25% and 57.14%, respectively. The former project was better because it decreased the false positive rate at a lower running cost. Conclusion The DT-LC is an effective screening strategy for second trimester detection of fetal Down's syndrome in mainland China.     

怀化市孕中期唐氏综合征的血清筛查和产前诊断分析

目的探讨孕中期采用甲胎蛋白(AFP)、游离β-绒毛膜促性腺激素(Free-β-HCG)、游离E3(uE3)联合筛查法在孕中期筛查唐氏综合征(DS)、神经管缺陷(NTD)及其他胎儿异常的可行性。方法应用时间分辨免疫荧光法检测孕妇血清中AFP、Free-β-HCG、uE3浓度,结合母龄、体重、孕周等个体参数,经过软件计算风险率;对高风险孕妇在知情的情况下,自愿选择进行染色体核型分析。结果 12 559例样本共筛查出高危孕妇862例,其中457例进行羊水染色体核型诊断;检出唐氏综合征儿16例,染色体结构异常27例,染色体多态11例。结论孕中期应用母血清三联法筛查,结合产前诊断是减少出生缺陷发生的有效手段之一。     

The prediction of adverse pregnancy outcome using low unconjugated estriol in the second trimester of pregnancy without risk of Down's syndrome

To investigate the relationship between low unconjugated estriol (uE3) levels in the second trimester and adverse perinatal outcomes in pregnancies without increased risk for Down's syndrome, 1,096 women under 35 years of age underwent a mid-trimester AFP-hCG-uE3 screening test between January 1995 and June 1998. Multiple pregnancies, maternal diabetes, smoking and elevation of AFP and hCG levels more than 2.0 multiple of median (MoM) were excluded from our study population. The results were divided into a low-uE3 group with uE3 levels at or below 0.75 MoM and a normal uE3 group with uE3 levels above 0.75 MoM. The risk for adverse pregnancy outcome was compared between the two groups and the role of low uE3 as a predictor of adverse pregnancy outcome was determined. The data were assessed using chi 2 or Fisher exact test and then logistic regression was used for the final analysis. The odds ratio (OR) and corresponding 95% confidence intervals (CI) were also calculated. Unconjugated E3 levels at or below 0.75 MoM was significantly associated with fetal growth restriction after adjustment for maternal age, weight, sampling weeks, AFP and hCG levels (OR 0.413, 95% CI 0.174-0.900; P = 0.035). Low uE3 levels in the second-trimester could help in the detection of fetal growth restriction by a low risk group in Down's syndrome. Careful gestational dating and serial clinical and sonographic assessment of fetal growth may be required for the clinician to manage these parturients.     

怀化地区7859例孕中期唐氏筛查和产前诊断结果分析

目的探讨孕中期唐氏筛查和产前诊断对检出胎儿染色体异常和妊娠不良结局的临床价值。方法应用时间分辨荧光免疫法对7859例孕中期(14-20周)妇女进行血清标记物三联方案(hA;FP+free-β-hCG+uE3)检测。筛查结果应用Multical软件计算21三体、18三体综合征和开放性神经管畸形的风险(rish)概率。对于高风险孕妇经遗传咨询,知情同意,自愿选择行产前诊断,于孕18-24周左右在超声引导下进行羊膜腔穿刺,抽取羊水培养进行胎儿染色体核型分析。并继续追踪胎儿和孕妇情况。结果在7859例孕妇中,筛查到高风险732例,唐氏筛查阳性率为7.65%(601/7859)。其中367例接受羊水或脐血穿刺产前诊断,占筛查高风险孕妇的50.13%(367/732);发现胎儿染色体异常16例,异常检出率4.36(16/367),其中6例唐氏综合征、5例18-三体综合征、4例Turner’s综合征、1例9号染色体臂间倒位。唐氏筛查高风险和低风险组不良妊娠结局分别为6.15%和1.46%,呈显著性差异(<0.05)。结论孕中期产前筛查是预测异常胎儿和不良妊娠结局的有效指标。结合羊水培养或脐血培养等产前诊断技术和方法,对预防先天缺陷儿出生、提高人口素质有重要临床应用价值。     

深圳地区44147例唐氏筛查临床分析

目的探讨早孕期和中孕期唐氏筛查对检出胎儿染色体异常的临床价值。方法 2008年1月至2010年12月,应用时间分辨荧光免疫法分别对11 328例早孕期（8～13＋6周）妇女和32 819例中孕期（14～20＋6周）妇女进行唐氏综合征的血清标记物检测。对于唐氏筛查高风险的孕妇,于孕16～22w进行羊膜腔穿刺,抽取羊水进行胎儿染色体核型分析。结果 11 328例早孕期妇女,627例唐氏筛查高风险;其中21-三体高风险596例,18-三体高风险31例。32 819例中孕期妇女,2072例唐氏筛查高风险;其中21-三体高风险1898例,18-三体高风险56例,神经管缺陷（NTD）高风险118例。其中,842例接受羊水穿刺（其中,早孕期高风险210例,中孕期高风险632例）,发现胎儿染色体异常39例（早期15例,中期24例）,异常检出率为4.63%。其中,羊水穿刺确诊18例唐氏综合征。4例18三体综合征。1例Turner＇s综合征1例47,XXX 9例9号染色体臂间倒位、其他6例。结论孕期唐氏筛查是预测胎儿染色体异常的有效指标。结合羊水培养,对预防先天缺陷儿出生有重要临床应用价值。     

孕妇孕中期唐氏综合征筛查血清AFP、Free-β-HCG、uE3中位数倍数的临床意义

目的探讨孕中期唐氏征筛查检查中AFP、Free-β-HCG、uE3中位数倍数（MOM）结果与胎儿染色体异常及其他先天畸形的关系。方法回顾性分析2009.1-2010.1在我院接受孕中期唐氏征筛查并成功随访的4250例单胎孕妇血清学筛查MOM（multiples of median）值结果与胎儿染色体异常及其他畸形发生情况。结果在4250例孕妇中,共筛查出有MOM值异常404例,其中染色体异常7例,神经管缺陷及其他畸形14例。血清学MOM值正常孕妇中发现21-三体1例,其他胎儿畸形13例,两组比较,胎儿染色体异常及其他畸形发生率有显著差距。结论孕中期血清学筛查指标MOM值异常对胎儿染色体异常,神经管缺陷及其他先天异常的发现均有一定的预测价值。     

南京地区9453例孕妇唐氏综合征产前筛查结果分析

目的探讨孕中期双联法在产前筛查唐氏综合征中的价值。方法采用时间分辨免疫荧光技术检测9453名15w-20＋6w孕妇血清中AFP和f-βHCG的浓度,使用Multicalc软件评估风险。建议唐氏综合征或爱德华综合征高风险孕妇行胎儿羊水/脐带血染色体检查,神经管开放性缺损高风险者接受高分辨度超声检查,并对高风险妊娠跟踪随访至胎儿出生后。结果共筛查出高风险343例,其中经产前诊断确诊唐氏综合征2例、爱德华综合征3例、其他染色体异常1例。通过随访发现其他异常4例。结论使用孕中期母血清AFP/f-βHCG双联法筛查出唐氏综合征等高风险妊娠进而行产前诊断是减少患儿出生的有效方法。     

Second-trimester maternal urine human chorionic gonadotrophin beta-core fragment concentrations in Asian pregnancies with fetal chromosomal abnormalities.

The aim of this study was to investigate the second trimester concentrations of maternal urine human chorionic gonadotrophin beta-core fragment (HCGbetacf) in Asian pregnanci2es with fetal chromosomal abnormalities. HCGbetacf concentrations were analysed from 34 urine samples in chromosomally abnormal pregnancies, including 28 cases of Down's syndrome, one case of trisomy 18, and five cases of other chromosomal abnormalities (one mosaic deletion and four translocations), and in a cohort of 268 normal pregnancies receiving second trimester amniocentesis. Results were normalized to urine creatinine (Cr) concentration and converted to the multiple of the median (MOM) concentration for the appropriate gestation. The median HCGbetacf MOM concentrations of Down's syndrome pregnancies (12.89) was significantly higher than that of normal pregnancies (1. 06) (P < 0.00001). Wide variations of HCGbetacf concentrations were observed in other chromosomally abnormal pregnancies. There were 18 of 28 (64%) Down's syndrome cases but one of five (20%) other chromosomally abnormal cases with HCGbetacf concentrations above the 95th centile of the control values (8.22 MOM cut-off). These findings suggest that HCGbetacf could be a potential marker in urine screening for fetal Down's syndrome in Asians.     

9969例孕中期孕妇产前筛查结果分析

目的分析孕中期母体血清hAFP、freeβ-HCG、uE3的变化及产前筛查的应用价值。方法采用时间分辨荧光免疫技术检测孕中期母体血清标志物hAFP、freeβ-HCG、uE3的含量,结合孕妇年龄、孕周、体重等因素用Risk2T软件进行风险评估,根据评估结果,将同孕周高、低风险孕妇的hAFP、freeβ-HCG、uE3含量进行统计分析;同时,建议高风险孕妇进一步确诊。结果低风险母体血清hAFP、uE3含量与孕周呈正相关,freeβ-HCG含量与孕周呈负相关;21-三体高风险母体血清hAFP、uE3含量明显低于低风险母体血清该指标含量,差异有统计学意义（P〈0.01）;而freeβ-HCG含量明显高于低风险时该指标含量,差异有统计学意义（P〈0.01）;18-三体高风险的母体血清hAFP、freeβ-HCG含量均低于低风险时该指标含量,差异有统计学意义（P〈0.01）。9969例孕妇中,筛查出21-三体、18-三体及NTD高风险共288例,筛查阳性率2.9%;107例进行了产前诊断,共确诊19例,确诊率为17.8%,分别为：21-三体6例、18-三体2例,NTD 3例,其他异常儿8例。结论孕中期母体血清3项指标呈规律性变化,检测该指标可发现高风险孕妇;产前筛查结合产前诊断能有效降低出生缺陷率。     

攀枝花地区2009～2011年孕中期产前筛查结果分析

目的分析攀枝花市2年半的产前筛查/产前诊断情况。方法对6907例孕15～20+6w单胎妇女进行血清甲胎蛋白(AFP)和游离绒毛膜促性腺激素(β-hCG)二联标志物的筛查,对高风险孕妇进行遗传咨询,在知情同意的情况下选择羊水染色体检查以明确诊断。结果 6907例经产前筛查有288例为高风险,筛查阳性率达4.17%;253例染色体高风险孕妇,经知情同意有159例进行羊水产前诊断,诊断率62.84%;确诊胎儿染色体异常2例,其中唐氏综合征1例、18-三体1例。经随访共发现不良妊娠结局29例,其中唐氏综合征新生儿1例;2年半内共发生3例假阴性,假阴性率达0.45‰。结论妊娠中期产前筛查/产前诊断是防止出生缺陷、提高出生人口素质的有效手段。     

1798例孕早中期整合筛查筛查效果分析

目的对比分析孕早中期整合筛查与孕中期三联产前筛查对检出胎儿染色体异常和神经管畸形的筛查效率,探讨整合筛查的临床价值,寻求更好的产前筛查模式。方法1798名孕早中期整合筛查孕妇孕早期（11w～13＋5w）检测血清标志物PAPP-A、Freeβ-HCG,同时B超测量胎儿颈项透明层厚度（NT）,于孕中期（15w～19＋6w）测定血清标志物AFP、Freeβ-HCG、uE3,同期4295名孕妇行孕中期三联筛查（检测母血清标志物AFP、Freeβ-HCG、uE3）,对筛查高风险孕妇进行后续产前诊断,并对妊娠结局进行随访,将两组筛查效果进行对比分析。结果整合筛查组高风险筛查高风险率1.06％,假阳性率0.95％,明显低于中期筛查组,两组差异有显著统计学意义。结论整合筛查组具有更低的假阳性率,避免了很多不必要的侵入性的产前诊断,是更有效的产前筛查模式。     

母血清筛查21三体、18三体阳性病例的产前诊断

目的探讨孕中期母血清筛查21-三体，18-三体阳性病例的染色体异常情况。方法AFP和Free-heG13用美国PE公司的时间分辨免疫荧光分析系统测定，风险值计算21-三体以1／270，18-三体以1／350为切割值。阳性病例进行羊膜腔穿刺羊水细胞培养。结果在54580例产前筛中有2615例为21-三体或18-三体阳性病例，占总筛查人数的4．79％。其中对1161例阳性病例进行了染色体分析（占总阳性数的44．4％）。结果发现29例异常核型，其中21-三体14例，18-三体5例，性染色体异常3例，其他异常核型7例，异常发生率2．49％。结论母血清产前筛查结合羊水诊断能够有效的避免胎儿染色体异常的发生。     

Predictive value of the triple screening test for the phenotype of Down syndrome.

Maternal serum alpha-fetoprotein (MSAFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) are routinely measured in the second trimester ("triple" test) and combined with maternal age to evaluate risk for fetal Down syndrome. Triple test results and clinical findings were retrospectively reviewed for 30 newborns with Down syndrome to determine whether analyte values or second trimester risks for Down syndrome were more extreme in affected pregnancies where cardiac or other severe congenital malformations were present compared to those cases where major anatomical abnormalities were absent. Mean MS-AFP, uE3, maternal age, and second trimester Down syndrome risk were all similar in the two groups of pregnancies. However, hCG concentrations did appear to be higher in the group of Down syndrome pregnancies with anatomical anomalies (mean 1.74 MoM versus 1.19 MoM) (P<0.05). Overall, there was no significant difference in the incidence of major anomalies in patients with screen-positive test results versus those cases that were not identified by the triple test. Prenatal counseling should therefore reflect the general expectations of the Down syndrome phenotype that have been established from live-born infants with this disorder.     

5933例孕中期母血清产前筛查回顾性分析与诊断

目的探讨孕中期母血清三联筛查法的临床意义及了解枣庄地区21-三体综合征（唐氏综合症）、18-三体综合征及NTD（神经管畸形）的发病率,旨在促进枣庄市产前筛查工作的更好开展。方法采用时间分辨荧光免疫分析法（DELFIA）对枣庄市产前诊断中心自2012年10月至2013年10月采集的5933个标本进行三联法孕中期母血清产前筛查。结果5933例孕妇中446例高风险,总体高风险率是7.5%;其中21-三体综合征高风险324例,高风险率是5.5%;18-三体高风险101例,高风险率是1.7%;NTD高风险21例,高风险率是0.4%。在自愿以及知情基础上经遗传咨询后有164例高风险孕妇行产前诊断,共确诊8例,确诊率是4.8%,其中21三体综合征4例,NTD 2例,畸胎瘤1例,三X综合征1例。结论结果表明孕中期母血清三联筛查法对于预测胎儿染色体病具有重要临床价值,可有效降低新生儿出生缺陷的发生;扩大产筛覆盖率,对实施出生干预工程,提高出生人口素质有重大意义。     

三种产前筛查方法的对比研究

目的探讨孕早期、中期和整合筛查对唐氏综合征筛查对检出胎儿染色体异常和妊娠不良结局的实用价值。方法应用时间分辨荧光免疫法对7802例孕9周～13+6周和11 911例孕15周～20+6周妇女进行血清标记物妊娠相关蛋白(PAPP-A)和游离β绒毛膜促性腺激素(freeβ-HCG)或甲胎蛋白(AFP)、游离β绒毛膜促性腺激素(freeβ-HCG)和游离雌三醇(uE3)进行检测,并对其中1014例孕妇进行整合筛查。筛查结果应用Lifecycle3.0软件计算唐氏综合征风险。唐氏综合征风险切割值为1∶270,当其值≥1∶270时为唐氏高危孕妇,于孕16周以后抽羊水或脐血进行胎儿核型分析,追踪胎儿和孕妇的情况。结果产前筛查19 713例孕妇,唐氏综合征筛查阳性孕妇1059例,假阳性率为5.37(1059/19713)。有607例接受了羊水或脐血穿刺产前诊断,占总筛查高危孕妇的57.32%(607/1059)。发现胎儿染色体异常24例,异常检出率为3.95%(24/607),其中4例唐氏综合征,3例18-三体,17例其他染色体异常,5例NTD畸形在孕中期筛查中发现。1例唐氏综合征在出生后被证实。三种筛查方法的假阳性率分别为:5.79%,5.10%,4.04%。结论三种筛查方法间存在显著性差异(P<0.05),整合筛查的假阳性率低于孕早期和孕中期筛查,如果有条件,我们推荐选择整合筛查。     

Prenatal screening for Down's syndrome with use of maternal serum markers.

BACKGROUND. Approximately 35 percent of all cases of Down's syndrome in fetuses can be detected by measuring maternal serum alpha-fetoprotein during the second trimester in the general population of pregnant women. Recent case-control studies indicate that this detection rate could be approximately doubled by measuring serum levels of unconjugated estriol and chorionic gonadotropin, which are abnormally low and abnormally high, respectively, in women carrying fetuses affected by Down's syndrome. METHODS. We prospectively screened 25,207 women and adolescents in the second trimester of pregnancy and assigned each a risk of fetal Down's syndrome with an algorithm that took into account measurements of all three serum markers in combination with maternal age. On this basis, 1661 subjects (6.6 percent) were initially assigned a second-trimester risk of fetal Down's syndrome of at least 1 in 190, and 962 (3.8 percent) were offered amniocentesis for chromosomal analysis after verification of gestational age. Gestational age was determined on the basis of the first day of the last menstrual period or, when available, by ultrasonography. RESULTS. Among the 760 women and adolescents who chose amniocentesis, 20 cases of fetal Down's syndrome were detected, along with 7 other chromosomal disorders. There was 1 additional case of fetal Down's syndrome among the 202 women who chose not to have amniocentesis. The rate of detection of Down's syndrome was thus 58 percent (21 of 36 expected cases), and the frequency of identifying a fetus with Down's syndrome in women undergoing amniocentesis was 1 per 38 amniocenteses (95 percent confidence interval, 1 in 25 to 1 in 62). CONCLUSIONS. Measuring serum alpha-fetoprotein, chorionic gonadotropin, and estriol is more effective in screening for fetal Down's syndrome than measuring maternal serum alpha-fetoprotein alone. Such an expanded protocol can readily be incorporated into existing prenatal screening programs.     

Predictive value of the triple screening test for the phenotype of Down syndrome

Maternal serum alpha-fetoprotein (MS-AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) are routinely measured in the second trimester (“triple” test) and combined with maternal age to evaluate risk for fetal Down syndrome. Triple test results and clinical findings were retrospectively reviewed for 30 newborns with Down syndrome to determine whether analyte values or second trimester risks for Down syndrome were more extreme in affected pregnancies where cardiac or other severe congenital malformations were present compared to those cases where major anatomical abnormalities were absent. Mean MS-AFP, uE3, maternal age, and second trimester Down syndrome risk were all similar in the two groups of pregnancies. However, hCG concentrations did appear to be higher in the group of Down syndrome pregnancies with anatomical anomalies (mean 1.74 MoM versus 1.19 MoM) (P < 0.05). Overall, there was no significant difference in the incidence of major anomalies in patients with screen-positive test results versus those cases that were not identified by the triple test. Prenatal counseling should therefore reflect the general expectations of the Down syndrome phenotype that have been established from live-born infants with this disorder. Am. J. Med. Genet. 85:123–126, 1999. © 1999 Wiley-Liss, Inc.     

孕早、中期血清学产前筛查染色体异常的效果分析

目的探讨不同孕期血清学产前筛查的实际效果。方法孕早期4297例孕妇采用PAPP-A＋free-β-hCG血清标志物进行产前筛查,孕中期28490例孕妇采用free-β-hCG＋AFP＋uE3三联血清标志物进行产前筛查,筛查结果应用Lifecycle.3.0软件计算唐氏综合征及18三体危险概率。对高风险孕妇进行羊水或脐血细胞染色体分析。结果孕早期高风险孕妇157例,产前确诊唐氏综合征患儿3例,孕中期高风险孕妇1978例,确诊唐氏综合征患儿15例,18三体5例,13三体1例。在本研究中孕早期的筛查假阳性率为3.34%,而孕中期组假阳性率为6.74%,明显高于孕早期组（P〈0.01）,假阳性率下降了50.45%。结论孕早期筛查模式要优于孕中期,孕早期接受筛查可显著降低参加产前诊断人数,避免了不必要的胎儿丢失。