Estimates of live birth prevalence of children with Down syndrome in the period 1991-2015 in the Netherlands

Why do individuals with Williams syndrome or Down syndrome fail the Weather Prediction Task?

Williams syndrome (WS) and Down syndrome (DS) are two neurodevelopmental disorders with distinct genetic origins characterized by mild to moderate intellectual disability. Individuals with WS or DS exhibit impaired hippocampus-dependent place learning and enhanced striatum-dependent spatial response learning. Here, we used the Weather Prediction Task (WPT), which can be solved using hippocampus- or striatum-dependent learning strategies, to determine whether individuals with WS or DS exhibit similar profiles outside the spatial domain. Only 10% of individuals with WS or DS solved the WPT. We further assessed whether a concurrent memory task could promote reliance on procedural learning to solve the WPT in individuals with WS but found that the concurrent task did not improve performance. To understand how the probabilistic cue-outcome associations influences WPT performance, and whether individuals with WS or DS can ignore distractors, we assessed performance using a visual learning task with differing reward contingencies, and a modified WPT with unpredictive cues. Both probabilistic feedback and distractors negatively impacted the performance of individuals with WS or DS. These findings are consistent with deficits in hippocampus-dependent learning and executive functions, and reveal the importance of congruent feedback and the minimization of distractors to optimize learning in these two populations.

Susceptibility to chromosome instability and occurrence of the regular form of Down syndrome in young couples

Although the risk of pregnancy with Down syndrome (DS) increases with age, conceptions with trisomy 21 can occur in mothers aged 35 or less. The micronucleus test on peripheral blood lymphocytes is a well-recognized method for studying chromosomal instability. The aim of this study was to evaluate the application of the micronucleus assay and fluorescence in situ hybridization (FISH) for estimation of chromosome instability and occurrence of trisomy 21 in young parents having pregnancy or a child with the regular form of Down syndrome. The study included 54 parents (27 couples) who had previous pregnancy with trisomy 21 at age 35 or less. The control group consisted of 30 couples with two healthy children and no previous spontaneous abortions. Parents with trisomy 21 pregnancy had significantly higher frequencies of micronuclei in binucleated cells. There was no statistically significant difference between the study and control groups in the frequencies of micronuclei in mononuclear cells, nuclear buds, or nucleoplasmic bridges. FISH analysis showed higher percentages of micronuclei containing whole chromosomes as well as statistically significant higher numbers of micronuclei containing chromosome 21 in the peripheral blood of DS parents. There was no statistically significant difference between the two groups in the responses of peripheral blood lymphocytes to treatment with the mutagen mitomycin C. Our results suggest that young parents with a history of the regular form of Down syndrome have a higher susceptibility to chromosome nondisjunction in peripheral blood lymphocytes. The micronucleus assay showed high specificity, but moderate sensitivity, for risk assessment of trisomy 21 pregnancy.

Changes in the number of babies born with Down syndrome in Japan

AIM

The number of babies born with Down syndrome has changed in recent years because of widespread availability of prenatal screening and advanced maternal age at delivery. In Japan, which has no public institutions that record data on babies born with chromosomal abnormalities (including Down syndrome), the accurate number remains unknown.

METHODS

The Japan Association of Obstetricians and Gynecologists Birth Defects Monitoring Program (hereafter the JAOG Program) is the only national survey of congenital anomalies in Japan. Using data from this survey and vital statistics, we investigated the changes in the number of babies born with Down syndrome in Japan from 2006 to 2019.

RESULTS

On performing linear regression analysis with the proportion of babies born with Down syndrome as the response variable, and the proportion of mothers giving birth at the age of 35 years or older as the explanatory variable, the regression coefficient was 0.0054 (p < 0.001). The proportion of mothers giving birth at the age of 35 years or older was useful for predicting the proportion of babies born with Down syndrome. This proportion has increased since 2006 but has remained almost unchanged since 2015. In 2019, it was 1/734.

CONCLUSIONS

This study revealed that the proportion of mothers giving birth at the age of 35 years or older strongly affected the proportion of babies born with Down syndrome. We assume that the proportion of babies is slightly affected by the increased number of pregnant women currently undergoing prenatal screening after the introduction of noninvasive prenatal genetic testing in 2013.

Down syndrome live births following assisted reproductive technology in Japan: a nationwide survey between 2007 and 2016

PURPOSE

The use of assisted reproductive technology (ART) and prenatal genetic testing have become more widespread in line with an increase in maternal age. However, the effect of the introduction of non-invasive prenatal testing (NIPT) in April 2013 on pregnancy outcomes in Japan, including the prevalence of Down syndrome live births following ART, has not been investigated. This study aimed to evaluate the trends in the prevalence of Down syndrome live births following ART in Japan.

METHODS

This population-based retrospective study used the Japanese nationwide ART registry. All clinical pregnancies resulting in live births, stillbirths, and termination of pregnancy (TOP) following ART from 2007 to 2016 were included. Pregnancy outcomes involving infants with Down syndrome were evaluated.

RESULTS

Among 351,808 pregnancies, the proportion of mothers with advanced age increased significantly from 2007 to 2016 (from 49.5 to 62.4% and 8.9 to 17.8% for mothers aged ≥ 35 and ≥ 40 years, respectively). The proportion of live births with Down syndrome was 77.3% in 2007, which remained consistent until 2012, but then decreased significantly to 45.1% after 2013 (P < 0.001). The prevalence of Down syndrome live births increased up to 2012 (19.5/10,000 live births), decreased significantly in 2013 (12.1/10,000 live births), and then remained almost stable (11.1-14.7/10,000 live births).

CONCLUSION

The introduction of NIPT balanced the prevalence of Down syndrome live births following ART with recent increasing maternal age in Japan.

Characteristics of Menarcheal Age, Menstrual Hygiene and Socio-Demographic Factors in Girls with Down Syndrome in Morocco

The purpose of this study was to determine the characteristics of menarcheal age, menstrual hygiene and their associated socio-demographic factors in girls with Down syndrome (DS) in Morocco. An analytical cross-sectional study was conducted between May 2014 and November 2017, including 59 parents/guardians of girls with Down syndrome aged 9-32 years. Data were collected through a standardized questionnaire providing information about socio-demographic and cultural conditions of parents, nutritional status and some functional abilities of girls. The median age at menarche was estimated using retrospective and status-quo methods, respectively. Data were entered and analyzed using the statistical program SPSS statistics software for Windows (version 20.0). Chi-square (χ2) and Mann-Whitney tests were used for testing statistical significance. The age at menarche ranged from 9 to 16 years old. The median was 13.0 (IQR, 11.0-14.0) years. The median age of menarche by probit analysis was 12.55 years. The relationship between menarcheal age, menstrual hygiene and the selected parameters showed a significant difference in age at menarche only regarding the parameter of number of siblings (Z = 2.14; p = .03), and in menstrual hygiene regarding mother's level of education, family size and age of talking (χ2 = 5.04, p = .02; χ2 = 3.75, p = .05 and χ2 = 4.99, p = .02, respectively). Most girls with DS attain menarche at the usual age as their counterparts in the general population and do not have enough knowledge about menstruation. Mobilization of all interventionists is urgent to develop adolescent skills about practices related to menstruation and menstrual hygiene.

Does non-invasive prenatal testing affect the livebirth prevalence of Down syndrome in the Netherlands? A population-based register study

Objective

To evaluate if non‐invasive prenatal testing (NIPT) affects livebirth (LB) prevalence of Down syndrome (DS) in the Netherlands.

Method

Data from clinical genetics laboratories and the Working Party on Prenatal Diagnosis and Therapy (2014–2018) and previous published data (1991–2013) were used to assess trends for DS LB prevalence and reduction percentage (the net decrease in DS LBs resulting from selective termination of pregnancies). Statistics Netherlands provided general population data.

Results

DS LB prevalence increased from 11.6/10,000 in 1991 to 15.9/10,000 in 2002 (regression coefficient 0.246 [95% CI: 0.105–0.388; p = 0.003]). After 2002, LB prevalence decreased to 11.3/10,000 in 2014 and further to 9.9/10,000 in 2018 (regression coefficient 0.234 (95% CI: −0.338 to −0.131; p < 0.001). The reduction percentage increased from 26% in 1991 to 55.2% in 2018 (regression coefficient 0.012 (95% CI: 0.010–0.013; p < 0.001)). There were no trend changes after introducing NIPT as second‐tier (2014) and first‐tier test (2017).

Conclusions

Introducing NIPT did not change the decreasing trend in DS LB prevalence and increasing trend in reduction percentage. These trends may be caused by a broader development of more prenatal testing that had already started before introducing NIPT.

What's already known about this topic?

The introduction of NIPT changed the landscape in prenatal screening worldwide.

No long‐term population‐based study on the impact of NIPT on DS LB prevalence has been published.

What does this study add?

This study shows how to calculate DS LB prevalence in the absence of a national registration program.

Introducing NIPT caused no trend changes in DS LB prevalence and reduction percentage in the Netherlands.

The Behavioral and Psychological Symptoms of Dementia in Down Syndrome Scale (BPSD-DS II): Optimization and Further Validation

BACKGROUND

People with Down syndrome (DS) are at high risk to develop Alzheimer's disease dementia (AD). Behavioral and psychological symptoms of dementia (BPSD) are common and may also serve as early signals for dementia. However, comprehensive evaluation scales for BPSD, adapted to DS, are lacking. Therefore, we previously developed the BPSD-DS scale to identify behavioral changes between the last six months and pre-existing life-long characteristic behavior.

OBJECTIVE

To optimize and further study the scale (discriminative ability and reliability) in a large representative DS study population.

METHODS

Optimization was based on item irrelevance and clinical experiences obtained in the initial study. Using the shortened and refined BPSD-DS II, informant interviews were conducted to evaluate 524 individuals with DS grouped according to dementia status: no dementia (DS, N = 292), questionable dementia (DS + Q, N = 119), and clinically diagnosed dementia (DS + AD, N = 113).

RESULTS

Comparing item change scores between groups revealed prominent changes in frequency and severity for anxious, sleep-related, irritable, restless/stereotypic, apathetic, depressive, and eating/drinking behavior. For most items, the proportion of individuals displaying an increased frequency was highest in DS + AD, intermediate in DS + Q, and lowest in DS. For various items within sections about anxious, sleep-related, irritable, apathetic, and depressive behaviors, the proportion of individuals showing an increased frequency was already substantial in DS + Q, suggesting that these changes may serve as early signals of AD in DS. Reliability data were promising.

CONCLUSION

The optimized scale yields largely similar results as obtained with the initial version. Systematically evaluating BPSD in DS may increase understanding of changes among caregivers and (timely) adaptation of care/treatment.

Down syndrome

Trisomy 21, the presence of a supernumerary chromosome 21, results in a collection of clinical features commonly known as Down syndrome (DS). DS is among the most genetically complex of the conditions that are compatible with human survival post-term, and the most frequent survivable autosomal aneuploidy. Mouse models of DS, involving trisomy of all or part of human chromosome 21 or orthologous mouse genomic regions, are providing valuable insights into the contribution of triplicated genes or groups of genes to the many clinical manifestations in DS. This endeavour is challenging, as there are >200 protein-coding genes on chromosome 21 and they can have direct and indirect effects on homeostasis in cells, tissues, organs and systems. Although this complexity poses formidable challenges to understanding the underlying molecular basis for each of the many clinical features of DS, it also provides opportunities for improving understanding of genetic mechanisms underlying the development and function of many cell types, tissues, organs and systems. Since the first description of trisomy 21, we have learned much about intellectual disability and genetic risk factors for congenital heart disease. The lower occurrence of solid tumours in individuals with DS supports the identification of chromosome 21 genes that protect against cancer when overexpressed. The universal occurrence of the histopathology of Alzheimer disease and the high prevalence of dementia in DS are providing insights into the pathology and treatment of Alzheimer disease. Clinical trials to ameliorate intellectual disability in DS signal a new era in which therapeutic interventions based on knowledge of the molecular pathophysiology of DS can now be explored; these efforts provide reasonable hope for the future.

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.

Management of contraceptives and menstrual complaints in patients with Down syndrome

Enhanced health care for patients with Down syndrome (DS) results in improved overall quality of life and longer life expectancy. The main gynecologic complaints of patients with DS and their caregivers relate to menstrual cycles, hygiene and reproductive issues. Certain aspects, such as age of menarche, menstrual cycles, internal genitalia, and hormone profile are similar to those observed in the general population. However, individuals with DS may have a higher incidence of other disorders related to menstruation, such as hypothyroidism, epilepsy and use of anticonvulsants. Contraceptive measures for individuals with DS can be used for both contraception and control of menstrual symptoms. The physician must be to make an individualized recommendation aimed at offering the most efficient and least invasive method with the fewest side effects. Among medical options are oral contraceptives, quarterly injectable medroxyprogesterone acetate, oral progesterone, a levonorgestrel-releasing intrauterine system, transdermal patch and vaginal rings. Surgical methods, including hysterectomy, endometrial ablation, or tubal ligation, are rarely considered because they raise ethical and legal questions. This article reviews the literature and basic guidelines to assist physicians who attend adolescent girls and women with DS to provide guidance on the appropriate management of the main gynecologic complaints of this population.

Social Cognition in Down Syndrome: Face Tuning in Face-Like Non-Face Images

Individuals with Down syndrome (DS) are widely believed to possess considerable socialization strengths. However, the findings on social cognition capabilities are controversial. In the present study, we investigated whether individuals with DS exhibit shortage in face tuning, one of the indispensable components of social cognition. For this purpose, we implemented a recently developed Face-n-Food paradigm with food-plate images composed of food ingredients such as fruits and vegetables. The key benefit of such face-like non-face images is that single elements do not facilitate face processing. In a spontaneous recognition task, 25 children with DS aged 9 to 18 years were presented with a set of Face-n-Food images bordering on the Giuseppe Arcimboldo style. The set of images was administered in a predetermined order from the least to most resembling a face. In DS individuals, thresholds for recognition of the Face-n-Food images as a face were drastically higher as compared not only with typically developing controls, but also with individuals with autistic spectrum disorders and Williams-Beuren syndrome. This outcome represents a significant step toward better conceptualization of the visual social world in DS and neurodevelopmental disorders in general.

National screening guidelines and developments in prenatal diagnoses and live births of Down syndrome in 1973-2016 in Denmark

INTRODUCTION

Denmark was the first country in the world to implement a national, free-for-all offer of prenatal screening for Down syndrome to all pregnant women. It has a high uptake (>90%) compared to other countries. Thus, Denmark offers an interesting case for investigating the consequences of implementing comprehensive, national prenatal screening guidelines. The aim of this study was to describe the historical developments in invasive procedures, pre-/postnatal diagnoses of Down syndrome and Down syndrome live births in the period 1973-2016 in Denmark.

MATERIAL AND METHODS

Data on invasive procedures, pre- and postnatal Down syndrome diagnoses were retrieved from the Danish Cytogenetic Central Registry.

RESULTS

From 1973 to 1993, screening based on maternal age and high-risk indications resulted in a constant increase in invasive procedures. After the introduction of the triple test in 1994, invasive procedures decreased for the first time in 20 years. Following the introduction of an offer of combined screening to all pregnant women in 2004, the number of invasive procedures decreased markedly, while there was a concurrent increase in prenatal diagnoses of Down syndrome. Additionally, the number of Down syndrome live births decreased suddenly and significantly, but subsequently stabilized at 23-35 annual live births. Of these, the majority were diagnosed postnatally.

CONCLUSION

Though prenatal screening technologies constantly improve, it was the introduction of and adherence to national guidelines that resulted in marked shifts in screening procedures and outcome in Denmark.

Low-Resolution Place and Response Learning Capacities in Down Syndrome

Down syndrome (DS), the most common genetic cause of intellectual disability, results from the partial or complete triplication of chromosome 21. Individuals with DS are impaired at using a high-resolution, allocentric spatial representation to learn and remember discrete locations in a controlled environment. Here, we assessed the capacity of individuals with DS to perform low-resolution spatial learning, depending on two competing memory systems: (1) the place learning system, which depends on the hippocampus and creates flexible relational representations of the environment; and (2) the response learning system, which depends on the striatum and creates fixed stimulus-response representations of behavioral actions. Individuals with DS exhibited a preservation of the low-resolution spatial learning capacities subserved by these two systems. In place learning, although the average performance of individuals with DS was lower than that of typically developing (TD) mental age (MA)-matched children and TD young adults, the number of individuals with DS performing above chance level did not differ from TD children. In response learning, the average performance of individuals with DS was lower than that of TD adults, but it did not differ from that of TD children. Moreover, the number of individuals with DS performing above chance level did not differ from TD adults, and was higher than that of TD children. In sum, whereas low-resolution place learning appears relatively preserved in individuals with DS, response learning appears facilitated. Our findings are consistent with the hypothesis that the neural pathways supporting low-resolution place learning and response learning are relatively preserved in DS.

A survey of undetected, clinically relevant chromosome abnormalities when replacing postnatal karyotyping by Whole Genome Sequencing

Whole genome sequencing (WGS) holds the potential to identify pathogenic gene mutations, copy number variation, uniparental disomy and structural rearrangements in a single genetic test. With its high diagnostic yield and decreasing costs, the question arises whether WGS can serve as a single test for all referrals to diagnostic genome laboratories ("one test fits all"). Here, we provide an estimate for the proportion of clinically relevant aberrations identified by light microscopy in postnatal referrals that would go undetected by WGS. To this end, we compiled the clinically relevant abnormal findings for each of the different referral categories in our laboratory during the period 2006-2015. We assumed that WGS would be performed on 300-500 bp DNA fragments with 150-bp paired sequence reads, and that the mean genome coverage is 30x, corresponding to current practice. For the detection of chromosomal mosaicism we set minimum thresholds of 10% for monosomy and 20% for trisomy. Based on the literature we assumed that balanced Robertsonian translocations and ∼9% of other, balanced chromosome rearrangements would not be detectable because of breakpoints in sequences of repetitive DNA. Based on our analysis of all 14,957 referrals, including 1455 abnormal cases, we show that at least 8.1% of these abnormalities would escape detection (corresponding to 0.79% of all referrals). The highest rate occurs in referrals of premature ovarian failure, as 73.3% of abnormalities would not be identified because of the frequent occurrence of low-level sex chromosome mosaicism. Among referrals of recurrent miscarriage, 25.6% of abnormalities would go undetected, mainly because of a high proportion of balanced Robertsonian translocations. In referrals of mental retardation (with or without multiple congenital anomalies) the abnormality would be missed in only 0.35% of referrals. These include cases without imbalances of unique DNA sequences but of clinical relevance, as for example, r(20) epilepsy syndrome. The expected shift to large-scale implementation of WGS ("one test fits most") as initial genetic test will be beneficial to patients and their families, since a cause for the clinical phenotype can be identified in more cases by a single genetic test at an early phase in the diagnostic process. However, a niche for genome analysis by light microscopy will remain. For example, in referrals of newborns with a suspicion of Down syndrome, karyotyping is not only a cost-effective method for providing a quick diagnosis, but also discriminates between trisomy 21 and a Robertsonian translocation involving chromosome 21. Thus, when replacing karyotyping by WGS, one must be aware of the rates and spectra of undetected abnormalities. In addition, it is equally important that requirements for cytogenetic follow-up studies are recognized.

Ethics of routine: a critical analysis of the concept of 'routinisation' in prenatal screening

In the debate surrounding the introduction of non-invasive prenatal testing (NIPT) in prenatal screening programmes, the concept of routinisation is often used to refer to concerns and potential negative consequences of the test. A literature analysis shows that routinisation has many different meanings, which can be distinguished in three major versions of the concept. Each of these versions comprises several inter-related fears and concerns regarding prenatal screening and particularly regarding NIPT in three areas: (1) informed choice, (2) freedom to choose and (3) consequences for people with a disability. Three of the strongest arguments raised under the flag of routinisation are assessed for their validity: the threat that NIPT poses to informed choice, the potential increase in uptake of first-trimester prenatal screening and its consequences for social pressure to participate in screening or terminate affected pregnancies, and the negative consequences for disabled people. These routinisation arguments lack empirical or normative ground. However, the results of this analysis do not imply that no attention should be paid to possible problems surrounding the introduction of NIPT. At least two problems remain and should be addressed: there should be an ongoing debate about the requirements of informed choice, particularly related to an expanded scope of prenatal screening. Also, reproductive autonomy can only be achieved when expecting parents' options are variegated, real and valuable, so that they can continue to choose whether or not to screen or to terminate a pregnancy.

The prevalence of the flat foot condition and insole prescription in people with Down's syndrome: a retrospective population-based study

[Purpose] The general approach for flat foot (FF) treatment in people with Down's syndrome (DS) is the use of insoles. However, the appropriate timing of the first insole prescription remains unclear. An aim of this present research was to investigate the status of prevalence of FF and orthosis prescription in the DS population. [Subjects and Methods] Two hundred fifteen subjects with DS who were seen at our hospital were retrospectively investigated. Investigated parameters were: prevalence of FF and other foot diseases, ratio and timing of orthopaedic consultation, ratio and timing of orthoses prescription, and mean age at the time of orthosis prescription. [Results] The prevalence of FF was 27.0% (58 subjects), and 50 subjects (23.3%) consulted an orthopaedic surgeon. An orthosis was prescribed for 54 subjects; 88.9% of these orthoses were insoles. Foot and leg orthoses other than insoles were prescribed significantly more frequently for females than males. The mean ages at the time of the first prescription of all types of orthoses and an insole were 7.3 years and 6.4 years, respectively. [Conclusion] The prevalence of FF was low, and the age at which subjects with DS were prescribed an orthosis was relatively high at our institution compared to previous reports. Since physical therapists see patients who could potentially have FF, those with suspected FF should then be referred to an orthopaedic doctor, which would enable the earlier orthosis prescription.

Older mothers and increased impact of prenatal screening: stable livebirth prevalence of trisomy 21 in the Netherlands for the period 2000-2013

In the Netherlands, there is no registry system regarding the livebirth prevalence of trisomy 21 (T21). In 2007, a national screening programme was introduced for all pregnant women, which may have changed the livebirth prevalence of T21. The aim of this study is to analyse trends in factors that influence livebirth prevalence of T21 and to estimate the livebirth prevalence of T21 for the period of 2000–2013. National data sets were used on the following: (1) livebirths according to maternal age and (2) prenatal testing and termination of pregnancy (ToP) following diagnosis of T21. These data are combined in a model that uses maternal age-specific risk on T21 and correction factors for natural foetal loss to assess livebirth prevalence of T21. The proportion of mothers aged ≥ 36 years has increased from 12.2% in 2000 to 16.6% in 2009, to gradually decrease afterwards to 15.2% in 2013. The number of invasive tests performed adjusted for total livebirths decreased (5.9% in 2000 vs. 3.2% in 2013) with 0.18% a year (95% CI: −0.21 to −0.15; p   < 0.001). Following invasive testing, a higher proportion of foetuses was diagnosed with T21 (1.6% in 2000 vs. 4.8% in 2013) with a significant increase of 0.22% a year (95% CI: 0.18–0.26; p < 0.001). The proportion of ToP subsequent to T21 diagnosis was on average 85.7%, with no clear time trend. This resulted in a stable T21 livebirth prevalence of 13.6 per 10,000 livebirths (regression coefficient −0.025 (95% CI: −0.126 to 0.77; p = 0.60).

Has noninvasive prenatal testing impacted termination of pregnancy and live birth rates of infants with Down syndrome?

BACKGROUND

Implementation of noninvasive prenatal testing (NIPT) as a highly accurate aneuploidy screening test has raised questions around whether the high uptake may result in more terminations of pregnancies and fewer births of children with Down syndrome (DS).

AIM

The aim of the study was to investigate the impact of NIPT on termination and live birth rates for DS.

METHODS

Literature reporting pregnancy outcomes following NIPT was reviewed. Termination rates were calculated for women with a high-risk NIPT result for DS. Two audits of pregnancy outcomes where NIPT indicated DS were conducted in the United Kingdom and Singapore.

RESULTS

Fourteen studies from the United States, Asia, Europe, and the United Kingdom were included in the review. Live births of children with DS were reported in 8 studies. Termination rates following NIPT were unchanged or decreased when compared to termination rates prior to the introduction of NIPT. Audits found 15 of 43 women in the United Kingdom and 2 of 6 in Singapore continued pregnancies following a high-risk NIPT result.

CONCLUSIONS

Termination rates following the detection of DS by NIPT are unchanged or decreased compared to historical termination rates. Impact on live birth rates may be minimal in settings where termination rates fall. Population-based studies are required to determine the true impact.

A third copy of the Down syndrome cell adhesion molecule (Dscam) causes synaptic and locomotor dysfunction in Drosophila

Down syndrome (DS) is caused by triplication of chromosome 21 (HSA21). It is characterised by intellectual disability and impaired motor coordination that arise from changes in brain volume, structure and function. However, the contribution of each HSA21 gene to these various phenotypes and to the causal alterations in neuronal and synaptic structure and function are largely unknown. Here we have investigated the effect of overexpression of the HSA21 gene DSCAM (Down syndrome cell adhesion molecule), on glutamatergic synaptic transmission and motor coordination, using Drosophila expressing three copies of Dscam1. Electrophysiological recordings of miniature and evoked excitatory junction potentials at the glutamatergic neuromuscular junction of Drosophila larvae showed that the extra copy of Dscam1 changed the properties of spontaneous and electrically-evoked transmitter release and strengthened short-term synaptic depression during high-frequency firing of the motor nerve. Behavioural analyses uncovered impaired locomotor coordination despite preserved gross motor function. This work identifies DSCAM as a candidate causative gene in DS that is sufficient to modify synaptic transmission and synaptic plasticity and cause a DS behavioural phenotype.

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Drosophila expressing a third copy of Dscam have altered neuromuscular transmission.

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Drosophila expressing a third copy of Dscam have deficits in locomotor coordination.

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Drosophila are a powerful system for studying single-gene effects in Down syndrome.