The impact of MSAFP screening on genetic services, 1984-1986

The impact of maternal serum alpha-fetoprotein (MSAFP) screening on genetic centers was investigated by a questionnaire mailed to 220 genetic centers in the United States. Eighty-four (38%) of centers responded to the questionnaire; of these (34%) were adequate for analysis. About 33% of the programs performed their own MSAFP testing. Approximately 70% of centers used 2.5 times the median (MoM) as a cutoff for MSAFP elevations and approximately 75% of centers used a sliding cutoff for low MSAFP based on both maternal age and the multiple of the median. Between 1984 and 1986, the total number of women screened by the reporting centers increased by about 4.7 fold. The percentage of women seen in their centers for prenatal counseling due to high or low MSAFP levels increased from 1.3% in 1984 to 13.1% in 1986. The percentage of prenatal diagnoses utilizing amniocentesis for high or low MSAFP increased from 3% in 1984 to 10% in 1986. During this period, 76 cases of Down syndrome were detected based on low MSAFP; this represents 1.7% of amniocenteses for low MSAFP. These data demonstrate a significant increase in the number of women seen for prenatal counseling and amniocentesis at the reporting genetic centers and is likely to represent a similar trend at all genetic centers. The impact of high MSAFP screening for neural tube defects and low MSAFP screening for Down syndrome is likely to increase over the coming years and genetic programs should prepare for the increasing utilization of services necessary to handle women with high and low MSAFP levels.     

Maternal serum alpha-fetoprotein screening and fetal chromosome anomalies: is lowering maternal age for amniocentesis preferable?

We have compared the cytogenetic abnormalities diagnosed prenatally in 1,098 patients referred for amniocentesis because of low maternal serum alpha-fetoprotein (MSAFP) to those of 445 patients whose indication was elevated MSAFP and those of 361 patients who had amniocentesis for "maternal anxiety." Autosomal trisomies, sex chromosome aberrations, and various structural rearrangements were detected in all 3 groups and actually exceeded the age-related incidence estimates. The frequency of chromosome anomalies in cases studied because of "maternal anxiety" with no prior screening was similar to that in the group referred for low MSAFP (1.38 and 1.27%, respectively). A relatively higher frequency (2.02%) was detected in the group whose indication was elevated MSAFP. Maternal serum screening is designed primarily to recalculate risk figures for Down syndrome, but not for other major chromosome abnormalities. The concept of prenatal screening for chromosome aberrations must therefore be reevaluated. We think that efforts should be directed at making amniocenteses more accessible to patients who request it. "Lowering" maternal age limits to 30 would encompass a greater proportion of pregnancies at risk and would be a step toward more effective prenatal diagnosis for chromosome abnormalities.     

Maternal serum α-fetoprotein screening and fetal chromosome anomalies: Is lowering maternal age for amniocentesis preferable?

We have compared the cytogenetic abnormalities diagnosed prenatally in 1,098 patients referred for amniocentesis because of low maternal serum α-fetoprotein (MSAFP) to those of 445 patients whose indication was elevated MSAFP and those of 361 patients who had amniocentesis for “maternal anxiety.” Autosomal trisomies, sex chromosome aberrations, and various structural rearrangements were detected in all 3 groups and actually exceeded the age-related incidence estimates. The frequency of chromosome anomalies in cases studied because of “maternal anxiety” with no prior screening was similar to that in the group referred for low MSAFP (1.38 and 1.27%, respectively). A relatively higher frequency (2.02%) was detected in the group whose indication was elevated MSAFP. Maternal serum screening is designed primarily to recalculate risk figures for Down syndrome, but not for other major chromosome abnormalities. The concept of prenatal screening for chromosome aberrations must therefore be reevaluated. We think that efforts should be directed at making amniocenteses more accessible to patients who request it. “Lowering” maternal age limits to 30 would encompass a greater proportion of pregnancies at risk and would be a step toward more effective prenatal diagnosis for chromosome abnormalities.     

Maternal serum alpha-fetoprotein screening for Down syndrome: economic considerations

The economic consequences of using an index of maternal age and maternal serum alpha-fetoprotein (MSAFP) screening to indicate risk of Down syndrome (DS) are examined. If DS screening indicated solely by a given maternal age is economically justifiable, then amniocentesis indicated by a DS risk equivalent to that maternal age cutoff, but based on an index of maternal age (for ages below the cutoff) and low MSAFP results, is also economically justifiable. It is concluded that the extant use of MSAFP screening for DS is a move toward the cost-effective use of scarce resources that can be made available with coordinated planning. However, increased professional and public awareness may result in significant increases in aggregate demand for these services. While MSAFP screening for DS is economically justifiable, there exists some potential for bottlenecks at the aggregate level, and these should be considered in conjunction with recommendations that the technology be adopted on a widespread basis.     

Familial risk of congenital heart defect

The economic consequences of using an index of maternal age and maternal serum alpha-fetoprotein (MSAFP) screening to indicate risk of Down syndrome (DS) are examined. If DS screening indicated solely by a given maternal age is economically justifiable, then amniocentesis indicated by a DS risk equivalent to that maternal age cutoff, but based on an index of maternal age (for ages below the cutoff) and low MSAFP results, is also economically justifiable. It is concluded that the extant use of MSAFP screening for DS is a move toward the cost-effective use of scarce resources that can be made available with coordinated planning. However, increased professional and public awareness may result in significant increases in aggregate demand for these services. While MSAFP screening for DS is economically justifiable, there exists some potential for bottlenecks at the aggregate level, and these should be considered in conjunction with recommendations that the technology be adopted on a widespread basis.     

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。     

The role of genetic counseling on decisions of pregnant women aged 35 years or over regarding amniocentesis in Turkey

We investigated the effects of genetic counseling given before amniocentesis that is given based on maternal serum screening (using the cut-off value of 1/250) and genetic sonogram results (+/- abnormal ultrasound marker) on pregnant women who are 35 years and older age. Their attitudes towards amniocentesis after genetic counseling were evaluated. Among 340 women, 223 (65.6%) were in the high-risk group and 117 (34.4%) were in the low-risk group according to non-invasive test results. After counseling, 216 pregnant women (167 cases have high-risk, 49 cases who had low-risk) decided to have amniocentesis while 124 women (56 with high-risk and 68 with low-risk) declined it. Fourteen abnormal karyotypes were detected. All pregnant women who had fetuses with chromosomal aberrations were in high-risk group. Our study shows that screening by non-invasive prenatal diagnostic tool has an effect on families' choice of amniocentesis. The use of these test results during counseling decreased the number of amniocentesis in a ratio of 36.5%.     

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。     

Chorionic villus sampling followed by amniocentesis in the same pregnancy

In our consecutive series of 2,574 chorionic villus sampling (CVS) patients, 146 women (5.7%) underwent a subsequent amniocentesis in the same pregnancy for the indications of absent or insufficient villi (3.3%), elevated maternal serum alpha-fetoprotein (0.93%), CVS mosaicism (0.89%), culture failure (0.23%), specimen contamination (0.15%), and CVS aneuploidy (0.12%). Patients presenting for a CVS should be informed of the possible need for a subsequent amniocentesis in the same pregnancy. There is a need for individual prenatal diagnosis programs to analyze their own data and provide genetic counseling information which pertains specifically to their institution. © 1993 Wiley-Liss, Inc.     

A controlled retrospective follow-up study of the impact of genetic counseling on parental reproduction following the birth of a Down syndrome child

Twenty-three couples who had received genetic counseling after the birth of a Down Syndrome child (DSC) were closely match-paired by race, religion, maternal age, paternal occupation, parental education and sex sibship order of the DSC with 23 non-counseled couples who had also had a DSC. When evaluated at least 1 1/2 years after the birth of the DSC or the genetic counseling, there were no significant differences between counseled and non-counseled couples in knowledge of general genetics or recurrent risks for Down Syndrome, initiation of subsequent pregnancies, or utilization of prenatal diagnosis. Knowledge of general genetics and recurrent risks for Down Syndrome among our post-counselees was poorer than that of two published immediate follow-up reports. Although 18 of 46 couples initiated at least one more pregnancy after the birth of their DSC, only three couples (2 counseled; 1 non-counseled) utilized prenatal diagnosis by amniocentesis.     

The Korean collaborative study on 11,000 prenatal genetic amniocentesis

Since amniocentesis made prenatal diagnosis feasible in 1967, the method has been remarkably instrumental in obstetrical practice. A recent study conducted between 1980 and 1997 collected 11,000 amniocentesis procedures done at 10 university hospitals and tertiary centers in Korea. The study indicated that the use of amniocentesis on patients has increased steadily since 1980; however, the number has increased sharply for patients in the mid 1990's. In the 1980's, amniocentesis had been used primarily for patients in advanced maternal age groups (at least 35 years or older). In 1995, amniocentesis had been implemented for the detection of abnormal serum markers (37.6%), and by 1997, amniocentesis was involved in such diagnosis even more frequently (44.8%). Of the total number of uses, 270 (2.5%) involved the detection of chromosomal anomaly. In autosomal disorders, 96 Down syndrome, 33 Edward syndrome, and 6 Patau syndrome were diagnosed. In sex chromosomal anomaly, 10 Turner syndrome, and 10 Klinefelter syndrome were diagnosed. Added to that, 83 translocations, and 15 mosaicisms were diagnosed. Of the 322 cases with abnormal ultrasonographic findings, 21 (6.5%) resulted in chromosomal anomaly. The use of genetic amniocentesis as a prenatal diagnostic test for Korean women has risen 10-fold between 1988 and 1998. As stated earlier, amniocentesis had earlier been used primarily for those in advanced maternal age groups. Today, maternal serum markers and highly sensitive ultrasonic technology can detect many fetal anomalies which eventually necessitate amniocentesis.     

义乌地区24756例孕中期产前筛查及随访结果分析

目的探讨孕中期母血产前筛查在临床中的应用和意义。方法应用时间分辨荧光免疫分析法检测孕中期孕妇血清中甲胎蛋白（AFP）、游离绒毛膜促性腺激素（Free-h CG）、未结合雌三醇（u E3）水平,用专用风险分析软件进行数据计算分析,对筛查出的高风险孕妇经优生遗传咨询,行羊水穿刺和产前超声检查。结果 24 756例孕妇中检出各类高风险人群共1491例,筛查阳性率6.02%;高风险孕妇中羊水穿刺率70.42%,妊娠结局随访率100%,胎儿异常发生率1.81%;低风险孕妇妊娠结局随访率96.05%,胎儿异常发生率0.42%。结论通过孕中期产前筛查和产前诊断,可减少缺陷儿的出生,加强随访能够更好的指导优生工作。     

California's experience with low MS-AFP results

The California AFP Screening Program was developed to offer pregnant women the opportunity to have their pregnancies screened for open neural tube defects (NTD). Because it is unwise to withhold potentially important clinical information about low MS-AFP results from the screened women and their physicians, follow-up diagnostic evaluations and counseling were offered to women with low MS-AFP results in addition to those with high results or positive family histories of NTD. Between April 7, 1986 and September 30, 1987, over 275,000 women voluntarily participated in the screening program. During the first year of the program 3,939 women were seen for follow-up evaluations due to low MS-AFP results. These evaluations occurred at state-approved AFP follow-up centers where ultrasonographic dating led to reinterpretation of 35% of the results. Of the remaining 2,552 (65%), 1,940 women (76%) had an amniocentesis. Sixteen Down syndrome fetuses were detected for a yield of 1/121 amniocenteses. Additional chromosome abnormalities included trisomies 18 and 13, Ullrich-Turner syndrome, (45,X), Klinefelter syndrome (47,XXY) and triploidy. The total yield of significant chromosome abnormalities was 1/78 amniocenteses.     

Prenatal diagnosis policy without routine amniocentesis in pregnancies with a positive family history for neural tube defects

The recurrence risk for neural tube defects in pregnancies of women with a family history of neural tube defects greatly exceeds the general population risk. In these high risk pregnancies, we used a prenatal diagnostic method differing from that usually employed, relying mainly on the results of maternal serum alpha-fetoprotein (MSAFP) and ultrasound examination, without routine amniocentesis. During the 6 years reviewed in this study, this method was applied in 539 pregnancies. Of a total of 20 neural tube defects, 19 were detected using this combination of MSAFP, ultrasound, and selective amniocentesis, and the authors estimate that about 8-10 spontaneous abortions were avoided because only 28 amniocenteses were carried out instead of 539. The risk of recurrence was found to be lower than that experienced earlier.     

佛山地区产前筛查与产前诊断分析研究

目的佛山地区产前筛查与产前诊断分析研究。方法选择自2006年1月～2008年12月来本院进行产前检查的孕妇共41 656例,其中有2 9101例自愿行血清学筛查,孕周为15～25周,年龄21～42岁,平均年龄为25.73岁。有41 333例行超声筛查,孕周11～36周。对唐氏筛查及B超筛查结果为高风险的孕妇进行遗传咨询,建议进行产前诊断确诊。产前诊断的方法采用羊膜腔穿刺羊水细胞培养或经腹脐静脉穿刺脐血细胞培养,染色体检查采用G带染色。结果在血清筛查2 9101例孕妇中,筛查出高风险3227例,阳性率为11.1%。其中21三体高风险1287例,占4.4%;18三体高风险423例,占1.45%。在血清筛查高风险的3227例孕妇中,接受产前诊断者1065例,占33%（1065/3227）。染色体核型异常者100例,占12.49%,占高风险孕妇的4.12%（100/3227）。其中21三体19例,18三体2例,检出率为1.97%（21/1065）,占染色体核型异常的21%（21/100）。有41 333例行超声筛查,超声检查筛查出高风险851例,阳性率为2.06%。行产前诊断206例,染色体异常45例,占21.84%（45/206）,其中检查出21三体5例,18三体8例,13三体1例,占染色体异常的31.11%（14/45）。结论将孕妇年龄、血清学检测和超声筛查作为产前筛查唐氏综合征的方法,明显提高了筛查阳性率,通过产前筛查将高风险的人群筛查出来作产前诊断,减少了缺陷儿出生。     

Maternal serum markers in screening for Down syndrome

The addition of two new markers in maternal serum, estriol and HCG, to those already known, namely the level of maternal serum alfa-fetoprotein and maternal age, considerably improves the expected results of a screening strategy for Down syndrome. The detection rate is slightly increased from 53.0% to 57.6%, but, more importantly, the false-positive rate decreases from 9.4% to 7.3%. It is our belief that, at least in women aged less than 35 years, a screening strategy based on a combination of maternal age and biochemical markers should be incorporated into antenatal care. For older women, the results of such a maternal serum test may refine counseling for genetic amniocentesis, as a much more explicit risk calculation can be performed than that based on age alone.     

孕中期产前筛查11716例分析

目的评价妊娠中期（AFP/β-hCG）唐氏综合征/神经管缺陷产前筛查系统产前筛查唐氏综合征和神经管缺陷的临床应用价值。方法采用酶联免疫分析11716例孕龄为14-20周,年龄为20-45岁妊娠妇女AFP/β-hCG,并结合孕妇年龄、孕周等其它因素,用唐氏综合征产前筛查风险估算和管理软件综合评价孕中期妇女妊娠唐氏综合征和神经管缺陷的风险度。结果检出唐氏综合征高危妊娠650例,筛查阳性率为5.54%,经过羊水染色体核型分析、出生缺陷监测和新生儿外周血染色体核型分析,共筛查出16例唐氏综合征患儿,而在低高危妊娠中发现1例唐氏综合征患儿。检出神经管缺陷高危妊娠60例,筛查阳性率为0.51%,均经过B超检查,共检出20例神经管缺陷胎儿;在11656例神经管缺陷低危妊娠中,未发现神经管缺陷患儿。结论AFP/β-hCG产前筛查扩大了孕妇人群,提高了唐氏综合征和神经管缺陷患儿的检出率,最大可能避免了这些缺陷儿的出生,同时也减少了因唐氏综合征和神经管缺陷导致的围产儿死亡,具有明显的经济效益和社会效益,也是落实优生优育政策非常有效的技术手段。     

The relevance of pre-amniocentesis pedigree analysis and genetic counseling

Prenatal diagnosis by amniocentesis in the second trimester of pregnancy has become widely accepted, and the demand for the procedure is increasing exponentially. It is important to reevaluate critically the time and effort spent obtaining a detailed pedigree analysis and family history prior to amniocentesis. Two hundred unselected consecutive cases of women undergoing amniocentesis because of advanced maternal age were studied. One woman had a brother with Duchenne muscular dystrophy and she was found by CPK testing to be a carrier. The prenatal diagnosis revealed that she was carrying a male fetus with a 50% chance of being affected, and the couple decided to have a termination of the pregnancy. A variety of other familial disorders and teratogenic exposures which were found in the studied 200 families were further explored through genetic counseling. Additional reasons for the individual pre-amniocentesis counseling include reducing anxiety and responding to specific psychosocial aspects of the prenatal diagnosis procedure in particular families.     

Maternal serum alpha-fetoprotein and fetal trisomy-21 in women 35 years and older: implications for alpha-fetoprotein screening programs

A retrospective study of 3,411 women who underwent midtrimester amniocentesis for fetal chromosome analysis between June 1979 and August 1984 was performed to evaluate an association between low maternal serum alpha-fetoprotein (AFP) concentrations and Down syndrome (DS) pregnancies. A total of 71 pregnancies was found with abnormal fetal chromosomes; of these, 26 cases were trisomy-21 and 10 cases were trisomy-18. The maternal serum AFP in women with DS fetuses was relatively lower than levels in women with fetuses that had normal chromosomes. In addition, the AFP concentrations in amniotic fluid were decreased in cases involving DS fetuses. We have estimated the risks for DS pregnancy at all maternal ages and most serum AFP concentrations. Using these calculations, genetic counselors will be able to provide more accurate risk estimates for trisomy-21 following maternal serum AFP testing.     

A cost-benefit analysis of prenatal detection of Down syndrome and neural tube defects in older mothers

Infants of older mothers have an increased risk of Down syndrome. As public awareness of this disorder increases, so does the number of women requesting prenatal diagnosis for advanced maternal age. A cost-benefit analysis was done to determine the maternal age for which screening for Down syndrome is cost-beneficial. The analysis took into account the cases of neural tube defects which would be detected "incidentally" on amniocentesis, as all amniotic fluid samples have alpha fetoprotein levels measured. British Columbia (B.C.) provides a unique opportunity for such a study: single-year maternal age risk figures for Down syndrome based on virtually complete ascertainment are available; the Department of Medical Genetics Prenatal Diagnosis Clinic is the main referral centre for the province; B.C. has a universal medicare system which facilitates the calculation of medical costs and gives all women financially equal access to prenatal diagnosis. The study concludes that prenatal screening for Down syndrome is cost beneficial for women 34 years old or older at conception. A discount rate of 14% was chosen for this analysis and the effect of such a rate on the results is discussed.