Regional variations in prenatal screening across Australia: stepping towards a national policy framework

A clinical audit of combined first trimester screening and non-invasive prenatal testing offered to pregnant women in a regional Australian hospital

The records of women attending a large Australian regional hospital for antenatal care were retrospectively analysed to determine what proportion had undergone or been offered first trimester screening for fetal abnormalities; only 609 (54%) of 1114 women had undergone or been offered screening. Younger women, multiparous women and women living in rural Australia were less likely to be offered screening. Barriers to screening and solutions for overcoming these need to be identified to improve access and equality in antenatal screening for all women.

Population-based impact of noninvasive prenatal screening on screening and diagnostic testing for fetal aneuploidy

PurposeTo assess the population-wide impact of noninvasive prenatal screening (NIPS) on combined first-trimester screening (CFTS), early ultrasound (11-13 weeks), and invasive prenatal diagnosis in a state with over 73,000 births per year.MethodsAnalysis of population-based data from 2000 to 2015 including (i) invasive prenatal tests, (ii) CFTS uptake, and (iii) total births. Utilization of early ultrasound was analyzed before and after NIPS (2010-2015).ResultsInvasive testing decreased significantly by 39.6% from 2012 to 2015 despite steady births. More than half of all confirmed cases of trisomy 21 were ascertained by NIPS in 2015, despite NIPS comprising only 11.7% of total indications for invasive testing. CFTS uptake declined significantly from 77.5% in 2013 to 68.1% in 2015, but 11- to 13-week ultrasounds did not. In 2015, ultrasound abnormality replaced CFTS as the most common indication for invasive testing and chromosomal microarray was performed for 85.3% of all prenatal karyotypes.ConclusionPrenatal testing is now unequivocally in the genomic era. NIPS is now the screening test that precedes the majority of confirmed diagnoses of trisomy 21. The contributions of NIPS, early ultrasound, and chromosome microarray have led to unprecedented detection rates of major chromosome abnormalities, now found in 20% of all invasive tests.

Diagnostic performance and costs of contingent screening models for trisomy 21 incorporating non-invasive prenatal testing

BACKGROUND

Contingent screening for trisomy 21 using non-invasive prenatal testing has the potential to reduce invasive diagnostic testing and increase the detection of trisomy 21.

AIM

To describe the diagnostic and economic performance of prenatal screening models for trisomy 21 that use non-invasive prenatal testing as a contingent screen across a range of combined first trimester screening risk cut-offs from a public health system perspective.

METHODS

Using a hypothetical cohort of 300 000 pregnancies, we modelled the outcomes of 25 contingent non-invasive prenatal testing screening models and compared these to conventional screening, offering women with a high-risk (1 > 300) combined first trimester screening result an invasive test. The 25 models used a range of risk cut-offs. High-risk women were offered invasive testing. Intermediate-risk women were offered non-invasive prenatal testing. We report the cost of each model, detection rate, costs per diagnosis, invasive tests per diagnosis and the number of fetal losses per diagnosis.

RESULTS

The cost per prenatal diagnosis of trisomy 21 using the conventional model was $51 876 compared to the contingent models which varied from $49 309-66 686. The number of diagnoses and cost per diagnosis increased as the intermediate-risk threshold was lowered. Results were sensitive to trisomy 21 incidence, uptake of testing and cost of non-invasive prenatal testing.

CONCLUSION

Contingent non-invasive prenatal testing models using more sensitive combined first trimester screening risk cut-offs than conventional screening improved the detection rate of trisomy 21, reduced procedure-related fetal loss and could potentially be provided at a lower cost per diagnosis than conventional screening.

Factors associated with utilization of maternal serum screening for Down syndrome in mainland China: a cross-sectional study

BACKGROUND

Knowledge of the factors that influence maternal serum screening (MSS) service utilization can be used to develop health policies to promote equitable access to MSS and further diagnostic tests. The purpose of this study was to find the factors associated with utilization of MSS as well as the current status of service utilization in mainland China.

METHODS

This was a hospital-based cross-sectional study with respondents interviewed with a questionnaire designed based on Andersen's behavioral model. Descriptive statistics, univariate analysis, and multilevel logistic regression analysis were used to identify the factors associated with MSS utilization, and to explore potential methods to improve screening uptake.

RESULTS

A total of 8110 women who had given birth within the previous 7 days in one of 111 participating institutions from six provinces in mainland China were interviewed. Approximately 36% of the participants had used MSS. Women between 20 and 35 years, who resided in urban areas, were educated, were in a stable occupation, who had health knowledge, who attended maternal preparation classes, who had received eight or more prenatal checkups, who were from a region of higher social economic status, and who delivered in a tertiary healthcare institution were significantly more likely to use MSS than their counterparts. As compared with other factors, insufficient education is the single most important demographic factor for service underutilization.

CONCLUSIONS

Efforts should not only be made to target the population that underuses MSS, but the overall organization of MSS service delivery should be assessed during policy development to make access to MSS equitable to the entire population of mainland China.

Do National Frameworks Help in Local Policy Development? Lessons from Yukon about the Evergreen Child and Youth Mental Health Framework

National frameworks are often put forward as a tool for local policy development, but little is known about their effectiveness. In this case study, the usefulness of Canada's Evergreen National Child and Youth Mental Health Framework (Evergreen) is examined in the development of a Yukon Child and Youth Mental Health and Addictions Framework (CYMHAF). Evergreen content and processes and the reflections of key informants and the research team are analyzed. The findings suggest that national frameworks can play important roles at the program and strategic levels, saving time and money in developing local frameworks, strengthening rigour, and helping to build consensus among local policy-makers.

Impact of prenatal screening and diagnostic testing on trends in Down syndrome births and terminations in Western Australia 1980 to 2013

OBJECTIVE

To assess how prenatal screening and diagnostic testing have impacted the diagnosis, termination and birth prevalence of Down syndrome in Western Australia (1980-2013).

METHOD

We analysed trends in termination rates and birth prevalence of Down syndrome using aggregated data (1980-2013). We modelled the expected live-birth rate and prevalence of Down syndrome and compared different eras of screening and diagnosis with respect to the impact on live-birth rate and prevalence of Down syndrome.

RESULTS

Between 1980 and 2013, the rate of Down syndrome pregnancies increased, corresponding to a greater proportion of babies born to older women. Following the introduction of screening in 1994, the rate of live-born infants with Down syndrome reduced significantly (p = 0.001). The rate of terminations of pregnancy for Down syndrome remained stable over this period. In the absence of termination, the Down syndrome live-birth rate would have risen from 1.1 per 1000 to 2.17 per 1000 between 1980 and 2013.

CONCLUSION

Prenatal testing in Western Australia has reduced the birth prevalence of Down syndrome despite an increased rate of Down syndrome pregnancies. Most women for whom a prenatal diagnosis of fetal Down syndrome is made, chose to terminate the pregnancy (93%), and this proportion has not changed over the study period.

Screening for Down syndrome in the second trimester of pregnancy

Antenatal screening for fetal anomalies has provided women and their partners with information to make reproductive choices based on the risk of serious chromosomal or structural defects since the 1990s. Alternative tests include first-trimester screening (combined ultrasound and maternal serum markers), second-trimester maternal serum markers and noninvasive cell-free DNA testing. The recent recommendations by the Royal Australian and New Zealand College of Obstetrics and Gynaecology and the Human Genetics Society of Australasia against second-trimester triple testing are based on unsound performance criteria, raise several contestable issues around access and equity and challenge the principles of governments providing affordable options.

National decline in invasive prenatal diagnostic procedures in association with uptake of combined first trimester and cell-free DNA aneuploidy screening

In late 2012, a new screening test for fetal aneuploidy based on circulating cell-free DNA (cfDNA) became available to Australian women. The introduction of this technology in the United States has led to a reduction in invasive diagnostic procedures. Analysis of the number of amniocentesis and chorionic villus sampling (CVS) procedures performed in Australia from 1994 to 2014 shows that the introduction of cfDNA testing has been associated with the most rapid decline in invasive procedures in the last 20 years. This change has important implications for training in, and maintenance of, the procedural skills of amniocentesis and CVS.

Rates of prenatal screening across health care regions in Ontario, Canada: a retrospective cohort study

BACKGROUND

It is recommended that all pregnant women be offered screening for Down syndrome and open neural tube defects, but emerging prenatal tests that are not publicly insured may compromise access. We evaluated screening rates for publicly insured screening tests across health care regions in the province of Ontario and determined whether maternal, provider or regional characteristics are associated with screening uptake.

METHODS

We conducted a population-based retrospective cohort study involving pregnant women in Ontario who were at or beyond 16 weeks' gestation in 2007-2009. We ascertained prenatal screening rates using linked health administrative and prenatal screening datasets. We examined maternal, provider and regional characteristics associated with screening uptake. Rate ratios (RRs) were estimated.

RESULTS

Of the 264 737 women included in the study, 62.2% received prenatal screening; uptake varied considerably by region (range 27.8%-80.3%). A greater proportion of women initiated screening in the first rather than the second trimester (50.0% v. 12.2%). Factors associated with lower screening rates included living in a rural area versus an urban area (adjusted rate ratio 0.64, 95% confidence interval [CI] 0.63-0.66), receiving first-trimester care from a family physician or midwife versus an obstetrician (adjusted rate ratio 0.91, 95% CI 0.90-0.92, and 0.40, 95% CI 0.38-0.43, respectively) and being in a lower income quintile (adjusted RR for lowest v. highest 0.95, 95% CI 0.94-0.96). Being an immigrant or a refugee was associated with higher screening rates.

INTERPRETATION

There were significant maternal, provider and regional differences in the uptake of prenatal screening across the province. With discrepancies expected to increase with the emergence of noninvasive prenatal tests paid for out of pocket by many women, policy efforts to reduce barriers to prenatal screening and optimize its availability are warranted.

Prenatal screening for Down syndrome in Australia: costs and benefits of current and novel screening strategies

OBJECTIVE

To analyse the cost-effectiveness and performance of noninvasive prenatal testing (NIPT) for high-risk pregnancies following first-trimester screening compared with current practice.

METHODS

A decision tree analysis was used to compare the costs and benefits of current practice of first-trimester screening with a testing pathway incorporating NIPT. We applied the model to 32 478 singleton pregnancies screened between January 2005 and December 2006, adding Medicare rebate data as a measure of public health system costs. The analyses reflect the actual uptake of screening and diagnostic testing and pregnancy outcomes in this cohort.

RESULTS

The introduction of NIPT would reduce the number of invasive diagnostic procedures and procedure-related fetal losses in high-risk women by 88%. If NIPT was adopted by all women identified as high risk by first-trimester combined screening, up to 7 additional Down syndrome fetuses could be confirmed. The cost per trisomy 21 case confirmed, including NIPT was 9.7% higher ($56,360) than the current prenatal testing strategy ($51,372) at a total cost of $3.91 million compared with $3.57 million over 2 years.

CONCLUSION

Based on the uptake of screening and diagnostic testing in a retrospective cohort of first-trimester screening in Western Australia, the implementation of NIPT would reduce the number of invasive diagnostic tests and the number of procedure-related fetal losses and increase the cost by 9.7% over two years. Policy planning and guidelines are urgently required to manage the funding and demand for NIPT services in Australia.

Factors affecting the quality of antenatal care provided to remote dwelling Aboriginal women in northern Australia

OBJECTIVE

there is a significant gap in pregnancy and birth outcomes for Australian Aboriginal and Torres Strait Islander women compared with other Australian women. The provision of appropriate and high quality antenatal care is one way of reducing these disparities. The aim of this study was to assess adherence to antenatal guidelines by clinicians and identify factors affecting the quality of antenatal care delivery to remote dwelling Aboriginal women.

SETTING AND DESIGN

a mixed method study drew data from 27 semi-structured interviews with clinicians and a retrospective cohort study of Aboriginal women from two remote communities in Northern Australia, who gave birth from 2004-2006 (n=412). Medical records from remote health centres and the regional hospital were audited.

MEASUREMENTS AND FINDINGS

the majority of women attended antenatal care and adherence to some routine antenatal screening guidelines was high. There was poor adherence to local guidelines for follow-up of highly prevalent problems including anaemia, smoking, urinary tract infections and sexually transmitted infections. Multiple factors influenced the quality of antenatal care.

KEY CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

the resourcing and organisation of health services and the beliefs, attitudes and practices of clinicians were the major factors affecting the quality of care. There is an urgent need to address the identified issues in order to achieve equity in women's access to high quality antenatal care with the aim of closing the gap in maternal and neonatal health outcomes.

'Give us the full story': overcoming the challenges to achieving informed choice about fetal anomaly screening in Australian Aboriginal communities

This cross-cultural qualitative study examined the ethical, language and cultural complexities around offering fetal anomaly screening in Australian Aboriginal communities. There were five study sites across the Northern Territory (NT), including urban and remote Aboriginal communities. In-depth interviews were conducted between October 2009 and August 2010, and included 35 interviews with 59 health providers and 33 interviews with 62 Aboriginal women. The findings show that while many providers espoused the importance of achieving equity in access to fetal anomaly screening, their actions were inconsistent with this ideal. Providers reported they often modified their practice depending on the characteristics of their client, including their English skills, the perception of the woman's interest in the tests and assumptions based on their risk profile and cultural background. Health providers were unsure whether it was better to tailor information to the specific needs of their client or to provide the same level of information to all clients. Very few Aboriginal women were aware of fetal anomaly screening. The research revealed they did want to be offered screening and wanted the 'full story' about all aspects of the tests. The communication processes advocated by Aboriginal women to improve understanding about screening included community discussions led by elders and educators. These processes promote culturally defined ways of sharing information, rather than the individualised, biomedical approaches to information-giving in the clinical setting. A different and arguably more ethical approach to introducing fetal anomaly screening would be to initiate dialogue with appropriate groups of women in the community, particularly young women, build relationships and utilise Aboriginal health workers. This could accommodate individual choice and broader cultural values and allow women to discuss the moral and philosophical debates surrounding fetal anomaly screening prior to the clinical encounter and within their own cultural space.

Hospital admissions in children with down syndrome: experience of a population-based cohort followed from birth

Objective

Children with Down syndrome, the most common genetic cause of intellectual disability, are prone to multiple and varied health-related problems. This study describes patterns of hospitalisations for children and young people with Down syndrome in Western Australia.

Methods

Birth records were linked to the Western Australian population-based Intellectual Disability database to identify all children born with Down syndrome in Western Australia between 1 January, 1983 and 31 December, 1999. These records were linked to the Hospital Morbidity Data System to provide information on all hospitalisations up to 31 December, 2004. Hospitalisation data, coded using ICD-9CM or ICD-10 (v0.5) were grouped into clinically relevant categories using the primary diagnosis. Rates of hospital admission for all and specific diagnoses were expressed in 1000-person-years at-risk and median age at first admission and length of stay were calculated.

Results

Of the 405 children, 395 had one or more hospital admissions, totalling 3786 admissions for all children and an estimated 39.5 person-years in hospital. On average, children were admitted 9.7 times, with an estimated rate of 757.2 admissions per 1000pyr (95% CI: 680, 843). A quarter of all admissions occurred in the first year of life. The average hospital length of stay was 3.8 days (95% CI: 3.7, 4.1). Upper respiratory tract conditions affected the most children (58.5%) and accounted for 12.1% of all admissions. Other disorders which affected a high percentage of children were ear/hearing conditions (50.6%), disorders of the oral cavity (38.0%) and lower respiratory tract conditions (37.5%). Overall, children with Down syndrome were hospitalised at a rate five times (95% CI = 4.3–6.2) that of the general population.

Conclusion

Children with Down syndrome are at increased risk of morbidity for varied causes underlining the importance of comprehensive and targeted primary care for this group.

Normal ranges for fetal nasal bone length determined by ultrasound at 18-20 weeks of gestation in a multiethnic Australian population

OBJECTIVE

Absence or hypoplasia of the nasal bone is commonly reported in Down syndrome fetuses. We define normal ranges and the 2.5th centile for fetal nasal bone length (NBL) in a multiethnic Australian population at 18-20 weeks of gestation.

METHODS

A prospective cohort study of women attending for a routine anomaly scan. Ethnicity of the patient and their partner was recorded, and the nasal bone was measured three times. Two methods of nasal bone assessment were used to define normal ranges: a single (first) measurement and the mean value of three measurements. Mixed-effects regression models were employed to account for interoperator differences treating sonographers as random effects. Nonparametric methods were used to define the 2.5th centile for gestational age.

RESULTS

A total of 1199 women were included with a mean gestational age 19.1 (SD 0.4; range 18-20) weeks. There is significant linear relationship between NBL and gestational age (P<0.001). The mean of three nasal bone measurements had a smaller standard deviation than single nasal bone measurements. Nonparametric assessment was used to define the 2.5th centile, which is 4.4 mm at 18 weeks and 5.0 mm at 20 weeks of gestation.

CONCLUSIONS

This study provides a reference range for fetal NBL at 18-20 weeks of gestation in an unselected multiethnic Australian population. Whilst NBL increases linearly from 18 to 20 weeks, the data are not normally distributed and nonparametric techniques are required to define the 2.5th centile. The mixed-effects model also accounts for variation in sonographer measurements.

Socio-demographic disparities in the uptake of prenatal screening and diagnosis in Western Australia

INTRODUCTION

Since the early 1980s, prenatal screening using ultrasound and biochemical markers has been used to refine the risk of Down syndrome and other fetal anomalies prior to considering fetal karyotyping. The performance of prenatal screening is subject to ongoing monitoring in Western Australia. The collection of these data can also assist in the identification of any potential inequities of access to prenatal screening within the state-wide programme.

METHODS

Prenatal screening data (2005-2006) were collected from accredited ultrasound and pathology laboratories in Western Australia. Screening data were linked to diagnostic and pregnancy outcome data. Performance characteristics of screening and uptake by socio-demographic characteristics were analysed.

RESULTS

Complete screening data were collected for 35,142 of the estimated 38,081 women screened during 2005 and 2006. There were 59,999 births related to this screening period. The lowest uptake of screening was among women who were Aboriginal (14.9%), living in remote areas (38.0%), under the age of 25 (40.2%), in the lowest quintile of the SEIFA index (41.6%) and with three or more children (48.4%). Logistic regression analysis showed all socio-demographic factors to be strongly associated with screening behaviour, with adjustment for ethnicity, socio-economic status, age, parity and area of residence.

DISCUSSION

Our results have important implications for the delivery of prenatal screening services in Western Australia. While the screening programme meets international and national performance standards, the disparities in screening uptake suggest inequity in access to services, particularly for Aboriginal, remote and socio-economically disadvantaged women.

Variation over time in medical conditions and health service utilization of children with Down syndrome

OBJECTIVES

To compare the prevalence of parent reported medical conditions and rates of health service utilization in school-aged children with Down syndrome in Western Australia in 1997 and 2004.

STUDY DESIGN

We compared two cross-sectional surveys completed by parents of children with Down syndrome identified from population-based sources in 1997 (n = 210) and 2004 (n = 208). Surveys collected information on family demographics, medical conditions, health issues, and service utilization. The analysis described medical conditions in 2004 and compared frequencies in both years. Regression analyses compared medical conditions and health utilisation in the two cohorts.

RESULTS

In 2004, children with Down syndrome had greater odds of having a bowel condition (OR, 1.69; 95%, 1.16 to 2.45; P = .01), were less likely to have a current problem due to their cardiac condition (OR, 0.32; 95% CI, 0.15 to 0.68, P = .003), and demonstrated an overall reduction in episodic illnesses and infections. The use of GP services (incidence rate ratio [IRR] = 0.91; 95% CI, 0.83 to 1.00, P = .05) and combined medical specialist visits (IRR = 0.92; 95% CI, 0.84 to 1.01; P = .09) were reduced in 2004, as were overnight hospital admissions (IRR = 0.60; 95% CI, 0.37 to 0.96; P = .03) and length of stay (IRR = 0.33; 95% CI, 0.24 to 0.44; P < .001).

CONCLUSIONS

The health status of children with Down syndrome has varied over time with reductions in current cardiac problems, episodic illnesses, and health service use. Research is now needed to investigate the impact of these changes on the overall health and quality of life of children and families living with Down syndrome.

The selective use of rapid aneuploidy screening in prenatal diagnosis

AIMS

To evaluate the diagnostic utility and costing of the selective use of rapid aneuploidy screening (RAS) for chorion villus sampling (CVS) and amniocentesis specimens.

METHODS

CVS and amniocenteses performed between 2000 and 2006 were identified. Cases were subdivided into two groups: (i) RAS in addition to long-term culture and (ii) long-term chromosome culture alone. The frequency of RAS, the proportion of abnormal results and the cytogenetic costings were reviewed.

RESULTS

A total of 3315 procedures were performed: 730 CVS and 2585 amniocenteses. An abnormal karyotype culture was present in 366 of 3315 (11%). For CVS an abnormal culture was present in 164 (22.5%). RAS (short-term culture/direct preparation) was selectively used in 399 cases (54.6%) with an abnormal result in 128 (32% of RAS). For amniocentesis, 206 chromosome abnormalities were present (8.0% of specimens). RAS (interphase FISH) was selectively used in 580 amniocenteses (22.4%). FISH was requested in 95 (66.4%) of the 143 abnormal cases potentially detectable with standard probes. There was a progressive increase in utilisation of RAS for amniocentesis (8.9% in 2000 to 43.3% of cases in 2006, P < 0.001). CVS RAS was stable. This liberalisation resulted in a fourfold increase in expenditure for FISH and cost/abnormality detected ($A970 per abnormal result in 2000 to $A4015 per abnormal result in 2006).

CONCLUSION

The selective use of prenatal RAS results in a reasonably high detection rate for chromosomal anomalies. Liberalisation of RAS, however, is an expensive cytogenetic model. An approach based on some predictive level of risk combined with resource funding levels may be a more pragmatic approach.

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.

Impact of a new national screening policy for Down's syndrome in Denmark: population based cohort study

OBJECTIVES

To evaluate the impact of a screening strategy in the first trimester, introduced in Denmark during 2004-6, on the number of infants born with Down's syndrome and the number of chorionic villus samplings and amniocenteses, and to determine detection and false positive rates in the screened population in 2005 and 2006.

DESIGN

Population based cohort study.

SETTING

19 Danish departments of gynaecology and obstetrics and a central cytogenetic registry 2000-7.

PARTICIPANTS

65 000 pregnancies per year.

MAIN OUTCOME MEASURES

The primary outcomes measured were number of fetuses and newborn infants with Down's syndrome diagnosed prenatally and postnatally and number of chorionic villus samplings and amniocenteses carried out. Secondary outcomes measured were number of women screened in 2005 and 2006, screen positive rate, and information on screening in 2005 and 2006 for infants with a postnatal diagnosis of Down's syndrome.

RESULTS

The number of infants born with Down's syndrome decreased from 55-65 per year during 2000-4 to 31 in 2005 and 32 in 2006. The total number of chorionic villus samplings and amniocenteses carried out decreased from 7524 in 2000 to 3510 in 2006. The detection rate in the screened population in 2005 was 86% (95% confidence interval 79% to 92%) and in 2006 was 93% (87% to 97%). The corresponding false positive rates were 3.9% (3.7% to 4.1%) and 3.3% (3.1% to 3.4%).

CONCLUSION

The introduction of a combined risk assessment during the first trimester at a national level in Denmark halved the number of infants born with Down's syndrome. The strategy also resulted in a sharp decline in the number of chorionic villus samplings and amniocenteses carried out, even before full implementation of the policy.