Prenatal genetic diagnosis and elective abortion in women over 35: utilization and relative impact on the birth prevalence of Down syndrome in Washington State

We have examined the relative contributions of a population-based antenatal detection program and unrestricted elective abortion used by women 35 years old and over in Washington State and King County for 1976--1977 to the declining birth prevalence of Down syndrome (DS). The amniocentesis/live birth (LB) ratio for women 35 years old and over was 20.5/100 LBs for King County and 11.7/100 LBs for Washington State in 1977. For the state in 1976, abortion ratios/1,000 LBs were 571 for women 35 to 39 years old and 1,096 for women 40 years old and over. Based on the total Washington State data, elective abortion has a greater impact on averting DS births than does the antenatal detection program. The impact of elective abortion appears to be related to its disproportionate use by women 35 years old and over compared to their contribution to the population of of LBs.     

Twenty-year trends in prevalence and survival of Down syndrome

The aims of this study were (1) to determine trends in total prevalence and live birth prevalence of Down syndrome, (2) to analyse trends in factors likely to influence this prevalence and (3) to determine 1-year survival in Down syndrome. A retrospective review was made of prospectively collected data on all cases of Down syndrome within a malformation registry born in 1985-2004. Down syndrome affected 1188 pregnancies among 690 215 live births (1.72 per 1000 total births). The proportion increased over 20 years from 1.3 to 2.5 per 1000 total births (P<0.0001). There were 389 terminations for Down syndrome and 51 stillbirths. There were 748 live births with Down syndrome (1.08 per 1000 live births). The live birth prevalence declined in 1985-1994 and increased in 1995-2004 with no overall change. Total live births in the population declined by 20% over 20 years. Mothers delivering at 35 years of age or above increased from 6 to 15%. The uptake of maternal serum screening increased from zero in 1987 to 35% in 1993 but then plateaued. One-year survival of live births with Down syndrome increased, especially in babies with cardiovascular malformations, reaching almost 100%. The prevalence of pregnancies affected by Down syndrome has increased significantly, but there has been no overall change in live birth prevalence. Increasing maternal age and improved survival of children with Down syndrome have offset the effects of prenatal diagnosis followed by the termination of pregnancy and declining general birth rate.     

AFP and age screening for Down syndrome

The availability of maternal serum alpha-fetoprotein (AFP) values from neural tube defect screening programmes offers the opportunity to improve the effectiveness of screening for Down syndrome. By appropriately combining information on maternal serum AFP and maternal age fewer women would need an amniocentesis to detect a given number of Down syndrome pregnancies or, for a given number of women having amniocentesis, more cases of Down syndrome would be detected than if age alone were used. For example to detect 40% of pregnancies with Down syndrome using AFP and age, 7% of women would need an amniocentesis compared with 11% using age alone. If an amniocentesis and a chromosome analysis together cost $1,000 this is equivalent to a saving of $37,000 per 1000 women screened. The use of AFP as well as age in Down syndrome screening allows patients to be better informed of their risk of having an affected pregnancy. For example, a 35-year-old woman has a risk of a Down syndrome term pregnancy of about 1:380, the risk is 1:120 if the AFP level is 0.40 multiples of the normal median (MoM) and 1:1800 if it is 2.50 MoM. Software providing computer assisted test interpretation has been produced to facilitate the estimation of risk and to identify women with positive screening results.     

Trends in the use of second trimester maternal serum screening from 1991 to 2003.

PURPOSE: To identify trends in the utilization of second trimester maternal serum screening, follow-up amniocenteses, and the detection of Down syndrome-affected pregnancies between 1991 and 2003. METHODS: We reviewed all triple and quadruple maternal serum screening tests referred to the University of Connecticut screening laboratory from women with singleton pregnancies. For each calendar year, the total number of tests, proportion to women aged 35 or older, number of follow-up amniocenteses, and the number of prenatally and postnatally diagnosed Down syndrome cases were recorded. RESULTS: A total of 109,469 women received screening. In 1991, the proportion of older women who received screening was 58% of that present in the Connecticut population but by 2003 this had increased to 83% (P < 0.001). In Down syndrome screen-positive pregnancies, there was no significant change in the rate of amniocentesis utilization (average 73%), but in false-positives, there was a decline from 70% in 1991 to 27% in 2003 (P < 0.001). CONCLUSION: Increased use of maternal serum screening by older women, use of second trimester ultrasound, and improvements in screening methodology have resulted in sharply reduced numbers of amniocenteses in unaffected pregnancies.     

The provision of information and informed decision-making on prenatal screening for Down syndrome: a questionnaire- and register-based survey in a non-selected population

Objective

Evaluating the information provision procedure about prenatal screening for Down syndrome, using informed decision-making as a quality-indicator.

Methods

Questionnaire- and register-based surveys. Midwives associated with 59 midwifery practices completed process data for 6435 pregnancies. Pregnant women (n = 510) completed questionnaires on informed decision-making.

Results

Midwives offered information to 98.5% of women; 62.6% of them wished to receive information, of these, 81.9% actually received information. Decision-relevant knowledge was adequate in 89.0% of responding women. Knowledge about Down syndrome was less adequate than knowledge about the screening program. Participants in the screening program had higher knowledge scores on Down syndrome and on the screening program than non-participants. Of the women who intended to participate (35.8%), 3.1% had inadequate knowledge. A total of 75.5% of women made an informed decision; 94.3% of women participating in the screening program, and 64.9% of women not participating.

Conclusion

This quality assurance study showed high levels of informed decision-making and a relatively low participation rate in the national screening program for Down syndrome in the Netherlands. Knowledge of the Down syndrome condition needs to be improved.

Practice implications

This evaluation may serve as a pilot study for quality monitoring studies at a national level.     

妊娠中期唐氏综合征和神经管缺损的产前筛查,诊断的研究

目的对重庆地区妊娠中期的妇女进行唐氏综合征和其他先天畸形的产前筛查、诊断,以降低出生缺陷。方法对43 057例14-20周的孕妇采用化学发光法孕妇血中的AFP和β-HCG浓度,通过计算机软件计算危险系数（唐筛风险值≥275,神经管缺损AFP≥2.5 MoMs）。对唐氏征高危的孕妇取羊水做染色体和基因诊断,神经管缺损高危者行超声波检查。结果 43 057孕妇中筛查出唐氏综合征,神经管缺损,18,13三体高危2463例,占5.72%。唐氏征高危2002例,占4.65%。有1352例愿意进一步确诊,发现53例异常妊娠。306例神经管缺损高危（占0.71%）中全部做超声检查。发现9例神经管缺损的胎儿。155例（占0.36%）18,13三体高危中86例做羊水染色体,异常1例,其余虽未做进一步确诊,但有3例胎死宫内,证明也有异常妊娠。结论唐氏综合征和神经管缺陷的产前筛查并结合其他方法进行诊断。对降低出生缺陷有积极的意义。     

Korean-specific parameter models for calculating the risk of Down syndrome in the second trimester of pregnancy

The purpose of the current study was to propose a Korean-specific parameter set for calculating the risk of Down syndrome in the second trimester of pregnancy and to determine the screening performances of triple and quadruple tests in Korean women. Using the data on triple or quadruple screening from three hospitals in Korea during 7 yr, we re-converted the concentrations of four serum markers to multiple of median values according to gestational age and maternal weight. After re-calculating the risk of Down syndrome in each pregnancy by multiplying maternal age-specific risk by the likelihood ratio values for the serum markers, screening performances and optimal cut-off values of triple and quadruple tests were analyzed. Among 16,077 pregnancies, 23 cases had Down syndrome (1.4/1,000 deliveries). Compared to the previous program, the tests with new parameters had improved screening performance. The triple and quadruple tests had detection rates of 65.2% and 72.7%, respectively, at a false-positive rate of 5%. The optimal cut-off value for the quadruple and triple tests was 1:250. We have presented a Korean-specific parameter set for Down syndrome screening. The proposed screening test using this parameter set may improve the performance of Down syndrome screening for Korean women.     

Equipoise of recent estimated Down syndrome live births in Japan

To support people with Down syndrome (DS), it is essential to know and predict the number of live births of children with this condition. In this study, we estimated DS live birth rates on the basis of maternal age distribution and numbers of births in the general population, the maternal‐age specific chance for a live birth of a child with DS, and the prenatal diagnosis/termination rate. The total number of live births in Japan decreased to less than 1 million in 2016 and the percentage of women aged 35 years old or over giving birth has increased by sixfold. Prenatal genetic testing in Japan has gradually become more widespread, and 20% of all cases of DS were diagnosed prenatally in 2016. Meanwhile, the annual projected number of DS live births has remained steady at around 2,200 (22 per 10,000 births). In 2016, it was estimated that 70% of all DS babies were born to women of advanced maternal age (AMA). Given that Japan is facing a decreasing birth rate and an aging population, adoption of the practice of prenatal genetic testing for AMA has balanced the number of DS births over the last 7 years from 2010.     

妊娠中期筛查唐氏综合征的临床研究

目的多项超声指标并结合血清相关指标对唐氏综合征（DS）在妊娠中期进行产前筛查,提高产前唐氏综合征的诊断率,获得本地区唐氏综合征的发病率。方法对大连市2007年10月-2008年3月,在门诊进行产前检查的孕妇行二联血清学及多项超声指标筛查。结果二联血清学筛查3212例,DS高危孕妇108例,有4例证实为DS患儿。超声检查1515例,DS高危共5例,均为21-三体综合征。两种方法共筛查出唐氏综合征6例。总筛查检出率为100％。唐氏综合征发生率为9．59／10000（20／20859）,活产新生儿唐氏综合征发生率为6．71／10000（14／20859）。结论多项超声指标结合血清相关指标对唐氏综合征在妊娠中期进行产前筛查,可以提高产前唐氏综合征的诊断率,对于减少出生缺陷发生率,具有重要的临床意义。     

What is the most relevant standard of success in assisted reproduction?: no single outcome measure is satisfactory when evaluating success in assisted reproduction; both twin births and singleton births should be counted as successes

The 2002 recommendation of the consensus meeting of the European Society of Human Reproduction and Embryology (ESHRE) that the outcome measure of assisted reproductive technology (ART) and non-ART should be 'singleton live birth rate' could profoundly effect the ability of infertility patients to become pregnant. We reviewed published reports and new data concerning elective single embryo transfer (eSET) vs. double embryo transfer (DET) and the outcome of twin pregnancies in the United States, as well as recommendations of other Societies concerning number of embryos to transfer and methods used to measure ART success. We found that no single outcome measure of ART is ideal. Mandatory eSET would result in 42%-70% fewer births compared to DET. Infertility treatments account for only 12% of all twin pregnancies and 4% of all premature births in the United States. Twin and singleton births due to ART do not occur earlier than spontaneously conceived twins and singletons unless they started as triplet and higher order pregnancies. Multiple outcome measures are necessary when evaluating ART success. Twin as well as singleton births should be counted as ART successes. The essential aim of infertility treatment should be a healthy low order (singleton or twin) birth.     

27例唐氏综合征患儿产前筛查的临床意义

目的收集27例血染色体确诊唐氏综合征患儿产妇的产前筛查资料,探讨中期血清三联筛查和妊娠中期超声筛查胎儿唐氏综合征的临床意义。方法回顾性分析2010年至2013年在我院分娩,单胎孕妇在妊娠14＋1~19＋6周行血清三联筛查,在妊娠18＋1~23＋6行超声筛查的孕妇及其新生儿的资料。结果在确诊唐氏综合征的患儿母亲中,产妇年龄大于35岁7例,血清三联筛查3例大于1：380。超声筛查异常8例,其中单发畸形1例,单独超声软标记5例,小于胎龄儿2例。结论建议在对血清三联筛查高危产妇密切随访的同时,应注重超声筛查显示的超声软标记,提高筛查效率,建议对高危产妇积极开展孕早期唐氏筛查。     

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.     

Trends in maternal age distribution and the live birth prevalence of Down's syndrome in England and Wales: 1938–2010

There have been concerns about the effects of increases in maternal age since the 1980s on the prevalence of Down''s syndrome. This study examined changes in the distribution of maternal age in England and Wales from 1938 to 2010. The live birth prevalence of Down''s syndrome in the absence of screening and subsequent termination was estimated using the numbers of babies born in England and Wales according to maternal age and the maternal age-related risk of a birth with Down''s syndrome. The proportion of women age 35 years or older at the time of giving birth reached a peak of 20% in 1945, declined to 5.5% in 1977 and rose to 20% in 2007. In the absence of screening and subsequent termination, the estimated live birth prevalence of Down''s syndrome would have mirrored these changes (2.3 per 1000 births in 1945, 1.2 per 1000 in 1976 and 2.2 per 1000 in 2007). The observed live birth prevalence (recorded by the National Down Syndrome Cytogenetic Register) was1.0 per 1000 from 1989 to 2010, due to screening and subsequent termination. In conclusion since the 1980s there has been an increase in the mean maternal age and in the expected prevalence of Down''s syndrome. When put in a longer historical context the current expected live birth prevalence is similar to that in the 1940s and the observed live birth prevalence is about 54% less than expected, due to screening and subsequent termination, and has remained reasonably constant since 1989 at 1.0 per 1000 births.     

1359例唐氏综合征筛查高危孕妇产前诊断结果分析

目的探讨对孕中期孕妇进行产前筛查、产前诊断的临床应用价值。方法对因唐氏综合征筛查高危孕妇,采取自愿的原则,抽羊水培养进行染色体核型分析。结果1359例唐氏综合征筛查高危孕妇中,核型异常者78例,阳性率5.74%,其中,21三体综合征21例,18三体综合征1例,13三体综合征2例,47,XXY4例,45,X05例,平衡易位2例,9号染色体倒位11例,其他染色体多态性32例占2.35%。年龄大于35岁孕妇核型异常者38例,占8.72%。结论对唐氏综合征筛查高危孕妇抽羊水进行产前诊断,可减少5.74%染色体异常儿的出生。     

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 screeing 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.     

Audiovisual information affects informed choice and experience of information in antenatal Down syndrome screening--a randomized controlled trial

Objective

To evaluate the effects of an information film on making an informed choice regarding Down syndrome screening, and women's knowledge and experiences of information.

Methods

Randomized controlled trial including 184 women in the intervention group and 206 controls recruited from maternity units in Stockholm, Sweden. The intervention was an information film presented as a complement to written and verbal information. Data were collected via a questionnaire in gestational week 27. Three different measures were combined to measure informed choice: attitudes towards Down syndrome screening, knowledge about Down syndrome and Down syndrome screening, and uptake of CUB (combined ultrasound and biochemical screening).

Results

In the intervention group 71.5% made an informed choice versus 62.4% in the control group. Women in the intervention group had significantly increased knowledge, and to a greater extent than the control group, experienced the information as being sufficient, comprehensible, and correct.

Conclusions

An information film tended to increase the number of women who made an informed choice about Down syndrome screening. Participants were more satisfied with the information received.

Practice implications

Access to correct, nondirective, and sufficient information is essential when making a choice about prenatal diagnostics. It is essential with equivalent information to all women.     

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。     

Prenatal cell-free DNA screening test failures: a systematic review of failure rates,risks of Down syndrome,and impact of repeat testing

PurposeWe systematically reviewed the published literature on test failure rates for the sequencing of cell-free DNA (cfDNA) in maternal plasma to identify Down syndrome.MethodsWe searched peer-reviewed English publications with diagnostic results on all pregnancies that provided test failure rates. Data on the odds of failure in Down syndrome and euploid pregnancies and the impact of repeat testing were extracted. Random-effects modeling was then used to identify moderators that could explain variability.ResultsThirty articles satisfied the inclusion criteria for overall failure rates. Study location (Western and Asian with initial testing, and Western with repeat testing) were significant moderators with failure rates of 3.3, 0.6, and 1.2%, respectively (P = 0.001). The odds ratio for Down syndrome in successful versus failed tests was 0.98 (95% confidence interval: 0.62–1.55, I² = 0%). Repeat testing from 14 large clinical cohort studies found that 83% (range: 52–100%) of failures were repeated, with 79% (range: 46–97%) being successful.ConclusionLower failure rates in Asian studies may be related to not routinely measuring the fetal fraction and to fewer obese women. Repeat cfDNA testing is effective in providing reliable results after initial failures. Protocols for primary cfDNA screening should focus on Down syndrome, with less common and more structurally abnormal trisomy 18 and 13 pregnancies treated as adjuncts.     

Human chromosome 21-specific DNA markers are useful in prenatal detection of Down syndrome

Trisomy 21 is the most common chromosomal aberration in live births. In this study we employed human chromosome 21-specific short tandem repeat (STR) DNA markers to determine the numbers of chromosome 21 present in fetal cells. Forty amniotic fluid samples from pregnancies complicated with fetal Down syndrome and 98 samples from euploid pregnancies were analyzed for D21S11 and interferon-alpha receptor (IFNAR) gene intervening sequence. Fluorescent dye-labeled primers were used in PCR amplification of these 2 markers. The PCR amplicon was analyzed with an automatic DNA sequence analyzer. The results showed that 35 of 40 fetal Down syndrome samples analyzed for IFNAR showed 3 distinct peaks, while 24 of 30 cases analyzed for D21S11 showed 3 distinct peaks. Two Down syndrome samples showed two uneven peaks. By analyzing 98 euploid pregnancies as controls, the ratios of area under the peaks were determined to be 1.31 +/- 0.22 and 1.96 +/- 0.18 (mean +/- SD) for the euploid pregnancies and pregnancies complicated by fetal Down syndrome with 2 peaks, respectively. Our data showed that altogether 39 of 40 (97.5%) Down syndrome cases were correctly identified based on either the 3-peak pattern in one or more of the DNA markers or the relative peak area ratio calculation. In conclusion, polymorphic STR DNA markers are useful for determining the numbers of chromosome 21 in fetal cells. The high sensitivity and automation of the procedures suggest a good prospect for use of this method in prenatal detection of fetal Down syndrome. However, this is a preliminary investigation and a large-scale study is necessary to validate the clinical application of this protocol.     

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。