Trends and geographic inequalities in the prevalence of Down syndrome in Europe, 1980-1999

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.

Can Individuals with Down Syndrome Benefit from Hippotherapy? An Exploratory Study on Gait and Balance

Purpose: To evaluate whether a hippotherapy protocol may influence balance and gait in patients with Down Syndrome (DS). Methods: Fifteen male patients affected by DS underwent a 6-month hippotherapy protocol. Stabilometric, baropodometric, and gait assessments were performed at baseline (T₀) and at the end of the treatment (T₁). Results: At baseline, DS patients showed a low bilateral hind foot pressure percentage at the baropodometric analysis, a high center of pressure area in the closed-eye condition, a high center of pressure sway in open- and closed-eyes recordings, a high medio-lateral and antero-posterior velocity oscillations in the closed eye condition, and a reduced step-length and velocity. After the 6-month, hippotherapy protocol, DS patients had a significant bilateral higher hindfoot pressure percentage. The stabilometric analysis revealed a lower center of pressure area in the closed-eye condition, and a significantly reduced center of pressure sway in open- and closed-eyes recordings. In addition, DS patients showed lower medio-lateral and antero-posterior velocity oscillations in the closed eye condition. Finally, hippotherapy significantly improved step length and velocity. Conclusions: This pilot study demonstrates that hippotherapy determines functional improvement in gait speed, width, bilateral symmetry, and balance in DS.

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.

Mothers of a child with Down syndrome: A qualitative analysis of the perspectives on non-invasive prenatal testing

OBJECTIVE

The introduction of non-invasive prenatal testing (NIPT) for Down syndrome (DS) has sparked social and ethical debates. To date, in-depth exploration of the voices of Australian mothers of a child with DS about NIPT has been lacking. The purpose of this study was to investigate the perspectives of Australian mothers of a child with DS towards the increasing availability of NIPT.

DESIGN AND SETTING

Fifteen mothers of children with DS aged 8 months-39 years participated in-depth interviews, conducted online via the software Zoom™. An inductive thematic analysis of interview data explored mothers' perceptions of NIPT.

FINDINGS

Mothers perspectives were nuanced and personal to each woman's circumstance. All mothers highlighted the inevitable association between testing and termination, the importance of autonomy and respecting [m]others' choices to test and to terminate, and that appropriate supports must be provided to ensure informed decision-making. These perspectives existed within an overarching theme of NIPT reflecting and reinforcing societal attitudes towards disability.

CONCLUSION

Mothers of a child with DS viewed informed decision-making as crucial both prior to undertaking NIPT and following a positive test result. This study adds a unique Australian perspective to the necessary ongoing social and ethical debate.

Prolonged toilet training in children with Down syndrome: a case-control study

OBJECTIVES

Children with Down syndrome have delayed psychomotor development, which is a factor that influences the level of difficulty in toilet training. The current study aims to estimate the age toilet training starts and completes in children with DS compared to children with normal psychomotor development and to evaluate the method and type of toilet training most frequently used, as well as its association with lower urinary tract symptoms and functional constipation.

METHODS

A case-control study was carried out from 2010 to 2015. All parents completed a questionnaire designed to assess the toilet training process. Lower urinary tract symptoms were assessed through the application of the Dysfunctional Voiding Symptom Score. The presence of functional constipation was assessed according to the Rome III criteria.

RESULTS

The study included 93 children with Down syndrome and 204 children with normal psychomotor development (control group [CG]). The mean age of toilet training onset was 22.8 months in those with DS and 17.5 months in the CG (p=0.001). In children with DS, the mean age when completing toilet training was 56.2 months and 27.1 months in the CG (p=0.001). Among children with DS, females completed toilet training earlier (p=0.02). The toilet training method used most often was child-oriented approach in both groups. No association was observed with the presence of lower urinary tract symptoms or functional constipation and the age of beginning and completing toilet training in both groups.

CONCLUSION

Children with Down syndrome experienced prolonged toilet training time. Prospective longitudinal studies are essential to gain insight into the toilet training of these children.

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

BACKGROUND

In Western countries, increasing maternal age has led to more pregnancies with a child with Down syndrome (DS). However, prenatal screening programs, diagnostic testing and termination of pregnancy influence the actual DS live birth (LB) prevalence as well. The aim of this study is to examine these factors in the Netherlands for the period 1991-2015. In our study, we establish a baseline for DS LB prevalence before non-invasive prenatal testing will be made available to all pregnant women in the Netherlands in 2017.

METHODS

Full nationwide data from the Dutch cytogenetic laboratories were used to evaluate the actual DS LB prevalence. In addition, nonselective DS prevalence, which is the DS LB prevalence that would be expected in absence of termination of pregnancies, was estimated on the basis of maternal age distribution in the general population.

RESULTS

Because of an increase in maternal age, nonselective DS prevalence increased from around 15.6 [95% confidence interval (CI) 13.9-17.4] per 10 000 LBs in 1991 (311 children in total) to around 22.6 (95% CI 20.3-24.9) per 10 000 in 2015 (385), the increase levelling off in recent years. Actual LB prevalence rose from around 11.6 (95% CI 10.9-12.2) per 10 000 in 1991 (230 children) to an estimated peak of 15.9 (95% CI 15.6-16.2) per 10 000 in 2002 (322), gradually decreasing since to 11.1 (95% CI 10.8-11.5) per 10 000 in 2015 (190). Reduction of DS LBs resulting from elective terminations had been fairly constant between 1995 and 2002 at around 28% and rose afterwards from 35% in 2003 to around 50% in 2015.

CONCLUSIONS

In spite of expansion of antenatal screening in the Netherlands in the 1990s and early 2000s, actual DS LB prevalence increased during this period. However, after 2002, this trend reversed, probably because of informing all pregnant women about prenatal testing since 2004 and the implementation of a national screening program in 2007.

Estimates of the live births, natural losses, and elective terminations with Down syndrome in the United States

The present and future live birth prevalence of Down syndrome (DS) is of practical importance for planning services and prioritizing research to support people living with the condition. Live birth prevalence is influenced by changes in prenatal screening technologies and policies. To predict the future impact of these changes, a model for estimating the live births of people with DS is required. In this study, we combine diverse and robust datasets with validated estimation techniques to describe the non-selective and live birth prevalence of DS in the United States from 1900-2010. Additionally, for the period 1974-2010, we estimate the impact of DS-related elective pregnancy terminations (following a prenatal diagnosis of DS) on the live births with DS. The live birth prevalence for DS in the most recent years (2006-2010) was estimated at 12.6 per 10,000 (95% CI 12.4-12.8), with around 5,300 births annually. During this period, an estimated 3,100 DS-related elective pregnancy terminations were performed in the U.S. annually. As of 2007, the estimated rates at which live births with DS were reduced as a consequence of DS-related elective pregnancy terminations were 30% (95% CI: 27.3-31.9) for the U.S. as a whole. Our results and our model provide data on the impact of elective pregnancy terminations on live births with DS and may provide a baseline from which future trends for live births with DS can be estimated.

Prevalence, prenatal screening and neonatal features in children with Down syndrome: a registry-based national study

Background

Down syndrome (DS) is one of the most common chromosomal abnormalities among newborns. In recent years advances in perinatal and neonatal care have improved chance of survival for the children with DS. The objective of this Registry-Based study was to get more accurate data of DS prevalence with evaluation of antenatal screening, neonatal and maternal features among total births in Croatia from 2009 to 2012.

Methods

We used retrospectively collected data for DS newborns from the medical birth database and perinatal mortality database for the period of 2009–2012. Differences between DS and the referent population for each year in quantitative measures were assessed with the independent t-test. Other differences in nominal and categorical values were analyzed with the chi-square test.

Results

The total prevalence for DS in the period of 2009–2012 was 7.01 per 10,000 births, while the live-birth prevalence was 6.49 per 10,000 births. The significant differences (p < 0.05) between the DS and reference populations for each year were noticed for birth weight and length, gestational age, mother age, Apgar score of ≥6 after 5 min and breastfeeding. Among newborns with DS, there were 64 (53.33 %) males and 56 (46.67 %) females versus 88,587 (51.76 %) males and 82,553 (48.23 %) females in the reference population. In the DS group compared to the reference population the mean birth weight was 2845 grams versus 3467 grams in males and 2834 grams versus 3329 grams in females, respectively, with a mean birth length of 47 cm versus 50 cm for both genders. The mean gestational age of the DS births was 37 weeks and the mean age of the mothers was 32.6 years, versus 39 weeks and 29.1 years, respectively, in the reference population. Only 68.3 % of children with DS were breastfed from birth, compared with 94.72 % of children in the reference population.

Conclusions

The significant differences for neonatal and maternal features between DS and the referent population were found similar to other studies. The total prevalence of DS in Croatia in the period of 2009–2012 was lower than the previously estimated prevalence based on EUROCAT data. The establishment of a new national registry of congenital malformations covering 99 % of all births in Croatia is necessary to improve the health and prosperity of children, adolescents and adults with DS in Croatia.

Monitoring the prevalence of severe intellectual disability in children across Europe: feasibility of a common database

AIM

Our aim was to study the feasibility of creating a framework for monitoring and undertaking collaborative research on intellectual disability at the European level, based on existing databases of children with such disability.

METHOD

The characteristics of five existing European intellectual disability databases from four countries (Iceland, Latvia, Ireland, and two in France), were discussed on the basis of ideal criteria set by a working group on childhood intellectual disability as part of the Surveillance of Cerebral Palsy in Europe Network (SCPE-NET). Mean prevalence values for severe intellectual disability for the birth years 1990 till 2002 were compared across databases.

RESULTS

Methods of case recruitment and diagnosis differed across databases, but classification of intellectual disability and completeness were similar. Severe intellectual disability (IQ<50) prevalence estimates were significantly (p<0.001) different across databases (south-east France: 3.3 out of 1000; south-west France: 3.0 out of 1000; Latvia: 3.9 out of 1000; Ireland: 5.0 out of 1000; and Iceland 5.1 out of 1000).

INTERPRETATION

In spite of differences in diagnosis and case inclusion across databases, the construction of a common database for severe intellectual disability was deemed feasible through harmonization of certain criteria, such as age, and through restriction to those with severe intellectual disability.

Prenatal treatment prevents learning deficit in Down syndrome model

Down syndrome is the most common genetic cause of mental retardation. Active fragments of neurotrophic factors release by astrocyte under the stimulation of vasoactive intestinal peptide, NAPVSIPQ (NAP) and SALLRSIPA (SAL) respectively, have shown therapeutic potential for developmental delay and learning deficits. Previous work demonstrated that NAP+SAL prevent developmental delay and glial deficit in Ts65Dn that is a well-characterized mouse model for Down syndrome. The objective of this study is to evaluate if prenatal treatment with these peptides prevents the learning deficit in the Ts65Dn mice. Pregnant Ts65Dn female and control pregnant females were randomly treated (intraperitoneal injection) on pregnancy days 8 through 12 with saline (placebo) or peptides (NAP 20 µg +SAL 20 µg) daily. Learning was assessed in the offspring (8–10 months) using the Morris Watermaze, which measures the latency to find the hidden platform (decrease in latency denotes learning). The investigators were blinded to the prenatal treatment and genotype. Pups were genotyped as trisomic (Down syndrome) or euploid (control) after completion of all tests. Statistical analysis: two-way ANOVA followed by Neuman-Keuls test for multiple comparisons, P<0.05 was used to denote statistical significance. Trisomic mice who prenatally received placebo (Down syndrome -placebo; n = 11) did not demonstrate learning over the five day period. DS mice that were prenatally exposed to peptides (Down syndrome-peptides; n = 10) learned significantly better than Down syndrome -placebo (p<0.01), and similar to control-placebo (n = 33) and control-peptide (n = 30). In conclusion prenatal treatment with the neuroprotective peptides (NAP+SAL) prevented learning deficits in a Down syndrome model. These findings highlight a possibility for the prevention of sequelae in Down syndrome and suggest a potential pregnancy intervention that may improve outcome.

Cytogenetic and epidemiological findings in Down syndrome: England and Wales 1989-2009

This study describes the characteristics of karyotypes leading to phenotypic Down syndrome (trisomy 21) in 29,256 cases diagnosed between 1989 and 2009 in England and Wales included in the National Down Syndrome Cytogenetic Register (NDSCR). The frequency of occurrence of the different karyotypes, proportions diagnosed prenatally, sex ratios, mean maternal age, and proportions of mothers with recurrences were analyzed. Nearly 97% of all cases were free trisomy 21; 2.9% contributory trisomy 21, 0.3% double or triple aneuploidies; 1% of all were mosaics. Mean maternal age of free trisomy 21 cases was 35 years, 54% were male, and 1% of mothers had recurrences. Free trisomy 21 mosaics had a lower mean maternal age (33 years), a lower proportion of males (39.5%), and 2.5% of mothers had recurrences. The majority of contributory translocations were Robertsonian or rea (21;21). Their mothers were younger, particularly those of Robertsonian translocations (28 years). Of the Robertsonian der (14;21) translocations of known parental origin, 54% were de novo, 41% maternal and 5% paternal and 15.8% of mothers of those of maternal origin had recurrences. Multiple aneuploidies have the highest proportion of males (67%), highest proportion of mosaics (40%), a mean maternal age of 37 years, and no mothers had a recurrence. The size of this national register allowed the frequency of occurrence of the rarer karyotypes of Down syndrome to be estimated and their epidemiology described.

Changes in yearly birth prevalence rates of children with Down syndrome in the period 1986-2007 in The Netherlands

BACKGROUND

The Netherlands are lacking reliable national empirical data in relation to the development of birth prevalence of Down syndrome. Our study aims at assessing valid national live birth prevalence rates for the period 1986-2007.

METHOD

On the basis of the annual child/adult ratio of Down syndrome diagnoses in five out of the eight Dutch cytogenetic centres, the national annual figures of the National Cytogenetic Network on total numbers of postnatal Down syndrome diagnoses were transformed into national figures on total numbers of postnatal Down syndrome diagnoses in newborn children only. In combination with the national annual data of the Working Group for Prenatal Diagnostics and Therapeutics on numbers of Down syndrome pregnancies not aborted after diagnosis, national figures on birth prevalence were constructed.

RESULTS

For the period 1986-2007, results based on the data of the cytogenetic centres are almost similar to the theory-based model data of de Graaf et al., with a small discrepancy of approximately 4%. Down syndrome birth prevalence in the Netherlands shows an upward trend from around 11 per 10,000 births in the early 1990s to around 14 per 10,000 births nowadays.

CONCLUSION

In spite of expansion of antenatal screening in the Netherlands, Down syndrome live birth prevalence has risen in the last two decades as a result of rising maternal age. This increase in Down syndrome birth prevalence is in contrast to studies from other European countries.

Congenital Heart Defects in Europe

Background—

This study determines the prevalence of Congenital Heart Defects (CHD), diagnosed prenatally or in infancy, and fetal and perinatal mortality associated with CHD in Europe.

Methods and Results—

Data were extracted from the European Surveillance of Congenital Anomalies central database for 29 population-based congenital anomaly registries in 16 European countries covering 3.3 million births during the period 2000 to 2005. CHD cases (n=26 598) comprised live births, fetal deaths from 20 weeks gestation, and terminations of pregnancy for fetal anomaly (TOPFA). The average total prevalence of CHD was 8.0 per 1000 births, and live birth prevalence was 7.2 per 1000 births, varying between countries. The total prevalence of nonchromosomal CHD was 7.0 per 1000 births, of which 3.6% were perinatal deaths, 20% prenatally diagnosed, and 5.6% TOPFA. Severe nonchromosomal CHD (ie, excluding ventricular septal defects, atrial septal defects, and pulmonary valve stenosis) occurred in 2.0 per 1000 births, of which 8.1% were perinatal deaths, 40% were prenatally diagnosed, and 14% were TOPFA (TOPFA range between countries 0% to 32%). Live-born CHD associated with Down syndrome occurred in 0.5 per 1000 births, with >4-fold variation between countries.

Conclusion—

Annually in the European Union, we estimate 36 000 children are live born with CHD and 3000 who are diagnosed with CHD die as a TOFPA, late fetal death, or early neonatal death. Investing in primary prevention and pathogenetic research is essential to reduce this burden, as well as continuing to improve cardiac services from in utero to adulthood.

Costs and end-of-life care in the NICU: lessons for the MICU?

Neonatal intensive care units (NICUs) and medical intensive care units (MICUs) are both very expensive. The cost-effectiveness of NICUs has been extensively evaluated, as has the long-term outcomes of subpopulations of NICU patients. NICU treatment is among the most cost-effective of high-tech interventions. And most patients do well. There are fewer evaluations of cost-effectiveness in the MICU and almost no long-term outcome studies. Policymakers who scrutinize expensive high-tech interventions would do well to study the examples found in the NICU.

How valid are the rates of Down syndrome internationally? Findings from the International Clearinghouse for Birth Defects Surveillance and Research

Rates of Down syndrome (DS) show considerable international variation, but a systematic assessment of this variation is lacking. The goal of this study was to develop and test a method to assess the validity of DS rates in surveillance programs, as an indicator of quality of ascertainment. The proposed method compares the observed number of cases with DS (livebirths plus elective pregnancy terminations, adjusted for spontaneous fetal losses that would have occurred if the pregnancy had been allowed to continue) in each single year of maternal age, with the expected number of cases based on the best-published data on rates by year of maternal age. To test this method we used data from birth years 2000 to 2005 from 32 surveillance programs of the International Clearinghouse for Birth Defects Surveillance and Research. We computed the adjusted observed versus expected ratio (aOE) of DS birth prevalence among women 25-44 years old. The aOE ratio was close to unity in 13 programs (the 95% confidence interval included 1), above 1 in 2 programs and below 1 in 18 programs (P < 0.05). These findings suggest that DS rates internationally can be evaluated simply and systematically, and underscores how adjusting for spontaneous fetal loss is crucial and feasible. The aOE ratio can help better interpret and compare the reported rates, measure the degree of under- or over-registration, and promote quality improvement in surveillance programs that will ultimately provide better data for research, service planning, and public health programs.

[Impact of maternal age distribution on the expected live birth prevalence of Down's syndrome in the metropolitan France between 1965 and 2008]

OBJECTIVES

To evaluate the impact of demographic factors such as maternal age on the expected prevalence of Down's syndrome at birth.

PATIENTS AND METHODS

We used data from the French National Institute of Statistics (INSEE) concerning live births and maternal age. Expected prevalence at birth is derived from a mathematical regression model commonly used in biochemical screening.

RESULTS

We present continuous expected prevalence at birth over a long period, from 1965 to 2008. Over the last three decades, mean maternal age has increased by 4 years, leading to a two-fold increased in the expected live-birth prevalence of Down's syndrome infants, from 12.1 per 10,000 in 1977 to 21.7 per 10,000 in 2008.

CONCLUSION

It is important to continue to consider the impact modifications in demographic factors, such as maternal age, particularly in the evaluation of screening practices and policies for Down's syndrome.

Prevalence of Down syndrome among children and adolescents in 10 regions of the United States

OBJECTIVE

We aimed to estimate the prevalence of Down syndrome (DS) among children and adolescents aged 0 to 19 years in 10 regions of the United States.

METHODS

This study was a cross-sectional analysis of live-born infants with DS during 1979-2003 from 10 population-based birth defects registries in the United States. We estimated the prevalence of DS at birth and among children aged 0 to 19 years in each region and in all regions pooled. The prevalence of DS among children and adolescents was calculated overall and according to age group, race/ethnicity, infant gender, and presence of a major heart defect.

RESULTS

From 1979 through 2003, the prevalence of DS at birth increased by 31.1%, from 9.0 to 11.8 per 10000 live births in 10 US regions. In 2002, the prevalence among children and adolescents (0-19 years old) was 10.3 per 10000. The prevalence of DS among children in a given age group consistently increased over time but decreased with age within a given birth cohort. The pooled prevalence of DS among children and adolescents was lower among non-Hispanic black individuals and other racial/ethnic groups compared with non-Hispanic white individuals; it was also lower among females than males.

CONCLUSIONS

This study provides prevalence estimates of DS among children and adolescents from 10 US regions. These estimates varied according to region, race/ethnicity, and gender, suggesting possible variation in prevalence at birth or in survival rates on the basis of these characteristics.

Prenatal testing for Down syndrome: comparison of screening practices in the UK and USA

Prenatal testing for Down Syndrome is a topic covered in every genetic counselor's training as it constitutes the main workload of genetic counselors in prenatal settings. Most Western countries nowadays offer some type of testing for Down Syndrome. However, practices vary according to country with regards to what tests are offered, insurance coverage and the legal situation concerning the option of terminating an affected pregnancy. In view of the growing interest in international genetic counseling issues, this article aims to compare prenatal testing practices in two English-speaking countries: the United Kingdom and the United States of America. A case will be presented to highlight some of the differences in practice. The topic underlines important implications for genetic counseling practice, such as patients' understanding of testing practices, risk perception, counseling provision and impact of prenatal testing results.

Prevention of developmental delays in a Down syndrome mouse model

OBJECTIVE

To estimate whether prenatal treatment with neuroprotective peptides prevents the developmental delay and the glial deficit in the Ts65Dn mouse model for Down syndrome and to explore the peptides' effects on achievement of normal development.

METHODS

Pregnant Ts65Dn females were randomly assigned to NAPVSIPQ+SALLRSIPA or control and were treated by investigators blinded to treatment and genotype on gestational days 8-12. Offspring were tested from postnatal day 5 to 21 for motor and sensory milestones with standardized tests by operators blinded to the pup's treatment and genotype. The pup's genotype was determined after completion of all tests. Activity-dependent neurotrophic factor, glial fibrillary acidic protein, and vasoactive intestinal peptide expression were determined using real-time polymerase chain reaction.

RESULTS

Trisomic mice achieved milestones with a significant delay in four of five motor and sensory milestones. Trisomic mice that were prenatally exposed to NAPVSIPQ+SALLRSIPA achieved developmental milestones at the same time as the controls in three of four motor and one of four sensory milestones (P<.01). Euploid pups prenatally treated with NAPVSIPQ+SALLRSIPA achieved developmental milestones significantly earlier than the euploid pups prenatally treated with placebo. Activity-dependent neurotrophic factor expression was significantly downregulated in the Ts65Dn brains compared with the controls, prenatal treatment with NAPVSIPQ+ SALLRSIPA prevented the activity-dependent neurotrophic factor decrease in the Ts65Dn brains, and the expression was not different from the controls. The glial marker glial fibrillary acidic protein demonstrated the known glial deficit in the Ts65Dn mice, and treatment with NAPVSIPQ+ SALLRSIPA prevented its downregulation. Lastly, vasoactive intestinal peptide levels were increased in the trisomic brains, whereas treatment with NAPVSIPQ+SALLRSIPA did not prevent its upregulation.

CONCLUSION

Prenatal treatment with NAPVSIPQ and SALLRSIPA prevented developmental delay and the glial deficit in Down syndrome. These findings highlight a possibility for the prevention of developmental sequelae in Down syndrome and suggest a potential intervention during pregnancy that may improve the outcome.

Has prenatal screening influenced the prevalence of comorbidities associated with Down syndrome and subsequent survival rates?

OBJECTIVES

With this study we aimed to compare survival rates for children with Down syndrome in 2 time periods, 1 before prenatal screening (1988-1990) and 1 contemporaneous with screening (1998-2000), and to examine the frequency of comorbidities and their influence on survival rates.

METHODS

Record-linkage was performed between the population-based Victorian Birth Defects Register and records of deaths in children up to 15 years of age collected under the auspice of the Consultative Council on Obstetric and Pediatric Mortality and Morbidity. Cases of Down syndrome were coded according to the presence or absence of comorbidities by using the International Classification of Diseases, Ninth Revision classification of birth defects. Kaplan-Meier survival functions and log rank tests for equality of survival distributions were performed.

RESULTS

Of infants liveborn with Down syndrome in 1998-2000, 90% survived to 5 years of age, compared with 86% in the earlier cohort. With fetal deaths excluded, the proportion of isolated Down syndrome cases in the earlier cohort was 48.7% compared with 46.1% in the most recent cohort. In 1988-1990 there was at least 1 cardiac defect in 41.1% of cases and in 45.4% in 1998-2000. There was significant variation in survival rates for the different comorbidity groupings in the 1988-1990 cohort, but this was not so evident in the 1998-2000 cohort.

CONCLUSIONS

Survival of children with Down syndrome continues to improve, and there is an overall survival figure of 90% to at least 5 years of age. It is clear from this study that prenatal screening technologies are not differentially ascertaining fetuses with Down syndrome and additional defects, because there has been no proportional increase in births of isolated cases with Down syndrome.

Is Down syndrome a disappearing birth defect?

OBJECTIVE

To assess trends in the prevalence of Down syndrome (DS) from 1986 to 2004 in Victoria, Australia (population approximately 5 million).

STUDY DESIGN

The Victorian Birth Defects Register and the Prenatal Diagnosis Database were linked to ascertain all cases of DS. Total and birth prevalence estimates were calculated per year and presented as 3-year moving averages.

RESULTS

The total number of cases of DS increased from 113 in 1986 to 188 in 2004. The number of births declined over the first decade of the study, particularly in younger women, but total numbers have fluctuated between 45 and 60 births since 1996. In women under age 35 years, total prevalence was 10/10,000 until 1997 and then increased to 12.5/10,000. In older women, total prevalence increased from 70/10,000 to 90/10,000 in this time frame. Birth prevalence declined at first but remained relatively stable in the later years of the study. The proportion of cases diagnosed prenatally increased from 3% to 60% in younger women.

CONCLUSIONS

Our findings demonstrate the continuing need to devote resources to support individuals with DS and their families.

Epidemiology of Down syndrome

Down syndrome (DS) is the most commonly identified genetic form of mental retardation and the leading cause of specific birth defects and medical conditions. Traditional epidemiological studies to determine the prevalence, cause, and clinical significance of the syndrome have been conducted over the last 100 years. DS has been estimated to occur in approximately 1 in 732 infants in the United States, although there is some evidence that variability in prevalence of estimates exist among racial/ethnic groups. Progress has been made in characterizing the specific types of chromosome errors that lead to DS and in identifying associated factors that increase the risk of chromosome 21 malsegregation, i.e., advanced maternal age and recombination. Studies to examine the variability of the presence of specific DS-associated birth defects and medical conditions provide evidence for genetic and environmental modifiers. Here, we provide a brief survey of studies that address the current state of the field and suggest gaps in research that can soon be filled with new multidisciplinary approaches and technological advances.

The prevalence of live birth Down syndrome in the region of Primorsko-goranska County in Croatia, 1996-2005: the impact of screening and amniocentesis

OBJECTIVES

To investigate the prevalence of live birth Down syndrome (DS) in the region of Primorsko-goranska County (PGC) in Croatia from 1996 to 2005 and to evaluate the impact of second-trimester maternal serum screening (MSS) and amniocentesis on live birth DS prevalence.

METHODS

Study was based on databases from the Department of Gynecology and Obstetrics, University Hospital Centre Rijeka, the Department of Biology and Medical Genetics, School of Medicine, University of Rijeka, and the Croatian National Institute of Public Health. The regional policy of prenatal diagnosis for DS includes amniocentesis for pregnant women aged 35 or over and MSS for younger women. We estimated live birth and total prevalence of DS and measured the proportion of pregnant women using MSS and amniocentesis. Trends of live birth and total prevalence of DS were tested by linear regression analysis.

RESULTS

The live birth prevalence of DS was 1.4/1000 in the period 1996-2005. A decreasing, but nonsignificant, trend of prevalence was observed over time (P = 0.577). Women aged 35 or over represented 11.6% of all pregnant women included in the study. The proportion of women who had MSS was 33.9%. The proportion who underwent amniocentesis was 6.1%.

CONCLUSIONS

No marked decrease in prevalence of live birth DS was observed in the region of PGC during the last 10 years. The usage of MSS and amniocentesis was too low to have any significant impact on live birth DS prevalence. Women's, as well as physician's, knowledge and attitudes towards prenatal diagnosis of DS should be evaluated.

Congenital heart defects--chromosomal anomalies, syndromes and extracardiac malformations

AIM

To register chromosomal anomalies, syndromes and extracardiac malformations in patients with Congenital heart defects (CHDs).

METHOD

Population-based prospective observational study.

RESULTS

Of 57 027 live births during 1982-2005, CHDs were detected in 662 (11.6 per 1000), of whom 146 (22%) had associated anomalies. Of these 52 (36%) had chromosomal anomalies (exclusive microdeletions), 26 (18%) genetic syndromes/microdeletions, 1 (0.7%) a teratogenous syndrome and 67 (46%) extracardiac malformations. In perimembraneous ventricular septal defects (VSDs), associated anomalies occurred in 22 of 70 (31%) compared to 27 of 298 (9%) in VSDs located in the muscular part of the septum (p < 0.0001). The prevalence of CHDs with associated disorders increased significantly from the cohort born during 1982-1993 to those born during 1994-2005 (2.0 vs. 3.1 per 1000, respectively; p < 0.0001), mainly caused by an increase of chromosomal trisomies (0.5 vs. 1.1 per 1000; p = 0.026). The percentage of women giving live birth at 35 years of age or more was 7.6% for the period 1982-1993 compared to 13.4% for 1994-2005 (p = 0.001).

CONCLUSIONS

Chromosomal anomalies, syndromes and extracardiac malformations occurred in nearly one-fourth of CHD cases. Muscular VSDs had a low prevalence of such conditions. The prevalence of CHDs with chromosomal trisomies increased, and was probably related to an increasing age of women giving birth.

Diagnostic yield of various genetic approaches in patients with unexplained developmental delay or mental retardation

The underlying cause of mental retardation remains unknown in up to 80% of patients. As chromosomal aberrations are the most common known cause of mental retardation, several new methods based on FISH, PCR, and array techniques have been developed over recent years to increase detection rate of subtle aneusomies initially of the gene rich subtelomeric regions, but nowadays also genome wide. As the reported detection rates vary widely between different reports and in order to compare the diagnostic yield of various investigations, we analyzed the diagnostic yield of conventional karyotyping, subtelomeric screening, molecular karyotyping, X-inactivation studies, and dysmorphological evaluation with targeted laboratory testing in unselected patients referred for developmental delay or mental retardation to our cytogenetic laboratory (n = 600) and to our genetic clinic (n = 570). In the cytogenetic group, 15% of patients showed a disease-related aberration, while various targeted analyses after dysmorphological investigation led to a diagnosis in about 20% in the genetic clinic group. When adding the patients with a cytogenetic aberration to the patient group seen in genetic clinic, an etiological diagnosis was established in about 40% of the combined study group. A conventional cytogenetic diagnosis was present in 16% of combined patients and a microdeletion syndrome was diagnosed in 5.3%, while subtelomeric screening revealed only 1.3% of causes. Molecular karyotyping with a 10 K SNP array in addition revealed 5% of underlying causes, but 29% of all diagnoses would have been detectable by molecular karyotyping. In those patients without a clear diagnosis, 5.6% of mothers of affected boys showed significant (>95%) skewing of X-inactivation suggesting X-linked mental retardation. The most common diagnoses with a frequency of more than 0.5% were Down syndrome (9.2%), common microdeletion 22q11.2 (2.4%), Williams-Beuren syndrome (1.3%), Fragile-X syndrome (1.2%), Cohen syndrome (0.7%), and monosomy 1p36.3 (0.6%). From our data, we suggest the following diagnostic procedure in patients with unexplained developmental delay or mental retardation: (1) Clinical/dysmorphological investigation with respective targeted analyses; (2) In the remaining patients without an etiological diagnosis, we suggest conventional karyotyping, X-inactivation screening in mothers of boys, and molecular karyotyping, if available. If molecular karyotyping is not available, subtelomeric screening should be performed.