Antenatal screening for cystic fibrosis: a trial of the couple model.

OBJECTIVE--To assess the delivery and acceptability of antenatal couple screening for cystic fibrosis. Carrier status was notified only when both members of a partnership had cystic fibrosis alleles and therefore a one in four risk of having an affected child. DESIGN--Mouthwash samples were tested when both partners participated. Results were returned only to positive couples. SETTING--Two large maternity hospitals in Edinburgh. SUBJECTS--Screening was offered to all couples who booked at one of the two hospitals. MAIN OUTCOME MEASURES--(a) The take up of screening, carriers and carrier couples identified, take up of prenatal diagnosis, and numbers of affected fetuses detected; (b) questionnaire measures of patient satisfaction and stress. RESULTS--Screening was offered to 8536 couples. 714 (8.4%) were regarded as ineligible, usually because of late booking or absence of a partner. 1900 (24.3%) of the remainder declined screening. Among the 5922 screened couples, four tested positive--that is, both partners were cystic fibrosis heterozygotes. All four elected to have prenatal diagnosis. There were three terminations of pregnancy because of an affected fetus, one couple having two successive pregnancies with affected fetuses. The participation rate was 76% for eligible couples (5922/7822) and 69% for all couples (5922/8536). Only 89 screened couples (1.5%) requested information on individual carrier status. No anxiety was detected among a cohort of the screened population, and 99% of questioned participants expressed satisfaction with the concept of couple screening. CONCLUSIONS--Antenatal couple screening is a satisfactory and acceptable way of screening for cystic fibrosis and has been adopted as routine in the two trial hospitals.     

The aims of expanded universal carrier screening: Autonomy,prevention, and responsible parenthood

Expanded universal carrier screening (EUCS) entails a population‐wide screening offer for multiple disease‐causing mutations simultaneously. Although there is much debate about the conditions under which EUCS can responsibly be introduced, there seems to be little discussion about its aim: providing carrier couples with options for autonomous reproductive choice. While this links in with current accounts of the aim of foetal anomaly screening, it is different from how the aim of ancestry‐based carrier screening has traditionally been understood: reducing the disease burden in the population. The reasons why the aim of EUCS is presented in terms of ‘autonomy’ rather than ‘prevention’ have not been spelled out in the literature. This paper seeks to fill this gap by considering the morally relevant similarities and dissimilarities between foetal anomaly screening, ancestry‐based carrier screening and EUCS. When carrier screening is performed in the prenatal period, enhancing autonomy appears the most appropriate aim of EUCS, as the alternative of ‘prevention through selective abortion’ would urge women to terminate wanted pregnancies. However, when screening is conducted in the preconception period, carrier couples can avoid the birth of affected children by other means than selective abortion, for instance preimplantation genetic diagnosis. To the extent that this increased control over passing on a genetic disorder raises questions of parental responsibility, it seems necessary that the account of the aims of EUCS is wider than only in terms of enhancing reproductive autonomy.     

Carrier screening for beta-thalassemia during pregnancy in India: a 7-year evaluation

AIM: Premarital screening for beta-thalassemia is not widely acceptable in India; hence, we evaluated the effectiveness of antenatal screening and counseling over 7 years. METHODS: 61,935 pregnant women were screened using the single-tube osmotic fragility test during their first antenatal visit. Individuals who were positive were investigated further for diagnosis of beta-thalassemia and other abnormal hemoglobins. Spouses of carrier women were tested whenever available. Couples at risk were given the option of prenatal diagnosis. RESULTS: Only 19% of the women registered at the antenatal clinic in the first trimester of pregnancy, and 14% of the women were positive per the osmotic fragility test; 1020 beta-thalassemia heterozygotes and 213 women with other hemoglobinopathies were identified, majority being in the second and third trimesters. Seven hundred and thirteen (69%) of their husbands could be tested, and 37 couples at risk were identified. Only 15 couples had a prenatal diagnosis done. Four couples with affected fetuses opted for termination of pregnancy. The remaining couples either did not respond after counseling or the pregnancies were advanced for prenatal intervention. CONCLUSION: This first large study shows that antenatal screening is acceptable in India; however, awareness generation is still a primary requisite to make women register early at antenatal clinics and bring their spouses for screening when required.     

Carrier screening for cystic fibrosis in a prenatal setting

Maternal prenatal cystic fibrosis (CF) screening was offered from September, 1997, to April, 1999, at the Ghent University Hospital, to couples undergoing prenatal diagnosis (amniocentesis) for reasons not related to CF. Fifteen minutes were devoted to explaining CF, CF screening, and the study protocol. The purpose was to assess the short- and long-term knowledge of CF, the attitude towards carrier screening, and carriership. A total of 314 couples entered the pilot study; 13 female CF carriers were identified. None of their partners carried an identifiable mutation. Our survey results show that information about CF and CF screening can be given effectively as part of antenatal care because most couples recalled important medical and genetic issues, valued the genetic test for CF, and seemed to cope well with the results. Risk estimates and actual numbers were more difficult to process and recall. From the small number of couples in which the woman alone was found to be a carrier, there was little or no evidence of marked distress.     

Cytogenetic survey in couples with recurrent fetal wastage

Summary Cytogenetic studies have been performed in 1068 couples with antecedent fetal wastage, i.e., at least two spontaneous first trimester abortions or one spontaneous first trimester abortion and one late fetal death, particularly with multiple congenital malformations.Three major types: 33 reciprocal translocations (3.09%), 20 Robertsonian translocations (1.87%) and six other chromosomal abnormalities (0.56%) were found, bringing the total number of chromosomal abnormalities to 59 (5.5%) in 1068 couples under investigation.In contrast to couples with reciprocal translocations, a high excess of female over male carriers was found in the group of Robertsonian translocations.In the evaluation of chromosomal polymorphisms, only variants with particularly large paracentromeric constitutive heterochromatin blocks were taken into account, and their low frequency in the present study is therefore not comparable with that in a general population.The impact of further extensive familial investigation on genetic counseling and the follow-up of prenatal diagnosis are discussed.     

Report on the Moscow symposium on biological research in schizophrenia

Abstract

Genetic counseling, second trimester amniocentesis, reliable techniques for analyzing fetal amniotic fluid and selective abortion together have the potential to prevent a variety of serious birth defects. Advances in technique and/or changing patterns of childbearing may place a large number of women in age groups where genetic counseling programs are recommended. However, attitudes toward abortion may be a critical variable in ascertaining the potential of genetic counseling programs to reduce birth defects. If opposition to abortion is based on a moral commitment, greater awareness of genetic counseling programs will lead to opposition to these programs. If attitudes toward abortion are based upon an evaluative process, such opposition is less likely to occur. Using a sample of women from the Rochester, New York, area (N = 1,616) whose attitudes toward abortion match U.S. estimates, we find that the greater the knowledge about prenatal screening, the less prevalent are attitudes opposed to abortion in circumstances necessary for birth defect reduction. This relationship holds when controlled for religion and family size. We conclude that educational and counseling programs concerning the potential benefits of prenatal screening are unlikely to arouse opposition to these programs.     

Contribution of ultrasonographic examination to the prenatal detection of trisomy 21: experience from 19 European registers

The objective of this study was to evaluate the contribution of ultrasound scanning to the prenatal detection of trisomy 21 in a large unselected European population. Data from 19 congenital malformation registers in 11 European countries were included. The prenatal ultrasound screening programs in the countries ranged from no routine screening to three ultrasound investigations per patient. Routine serum screening was offered in four of the 11 countries and routine screening on the basis of maternal age amniocentesis in all. The results show that overall 53% of cases of trisomy 21 were detected prenatally with a range from 3% in Lithuania to 88% in Paris. Ninety-eight percent of women whose babies were diagnosed before 24 weeks gestation chose to terminate the pregnancy. Centres/countries that offer serum screening do not have a significantly higher detection rate of trisomy 21 when compared to those that offer maternal age amniocentesis and anomaly scanning only. Fifty percent of trisomy 21 cases were born to women aged 35 years or more. In conclusions, second trimester ultrasound plays an important role in the prenatal diagnosis of trisomy 21. Of those cases prenatally diagnosed, 64% of cases in women <35 years and 36% of those in women >or=35 years were detected because of an ultrasound finding. Ultrasound soft markers accounted for 84% of the scan diagnoses. There is evidence of increasing maternal age across Europe with 50% of cases of trisomy 21 born to women aged 35 years or more.     

Active cascade testing for carriers of cystic fibrosis gene.

OBJECTIVE--To examine the acceptability, practicability, efficiency, and application of active screening for carriers of the cystic fibrosis gene in the extended families of those in whom the disease is present (Cascade screening). DESIGN--Paediatricians and physicians provide details of their affected patients, pedigrees are drawn up, and relatives offered tests after initial contact by the affected nuclear families. Affected patients are genotyped in a laboratory with a special interest in the genetics of cystic fibrosis. SETTING--North Western health region. SUBJECTS--Relatives and partners of 607 people with cystic fibrosis. INTERVENTIONS--Genetic counselling by letter for people found to be carriers; formal genetic counselling and when indicated arrangements for prenatal diagnosis for couples discovered to be carriers. MAIN OUTCOME MEASURES--Number of carrier couples detected; action in pregnancy of detected carrier couples; extent of the uptake of screening by relatives. RESULTS--Of 1563 relatives or partners tested, 15 carrier couples were detected; of nine pregnancies undertaken by these 15, eight had prenatal tests and three terminated pregnancies. An average of 16 people per family have come forward for testing so far. CONCLUSIONS--Cascade screening for carriers of cystic fibrosis is well accepted by relatives, especially on the mother''s side of the family; it is 10 times more efficient in detecting carrier couples than unfocused screening. Detected carrier couples make practical use of the information in pregnancy. Active cascade screening for carriers is effective in cystic fibrosis and widespread application is recommended. These principles could be applied to other recessive disorders.     

Postmarketing surveillance for human teratogenicity: a model approach.

BACKGROUND: Most congenital defects associated with prenatal exposures are notable for a pattern of major and minor malformations, rather than for a single major malformation. Thus, traditional epidemiological methods are not universally effective in identifying new teratogens. The purpose of this report is to outline a complementary approach that can be used in addition to other more established methods to provide the most comprehensive evaluation of prenatal exposures with respect to teratogenicity. METHODS: We describe a multicenter prospective cohort study design involving dysmorphological assessment of liveborn infants. This design uses the Organization of Teratology Information Services, a North American network of information providers who also collaborate for research purposes. Procedures for subject selection, methods for data collection, standard criteria for outcome classification, and the approach to analysis are detailed. RESULTS: The focused cohort study design allows for evaluation of a spectrum of adverse pregnancy outcomes ranging from spontaneous abortion to functional deficit. While sample sizes are typically inadequate to identify increased risks for single major malformations, the use of dysmorphological examinations to classify structural anomalies provides the unique advantage of screening for a pattern of malformation among exposed infants. CONCLUSIONS: As the known human teratogens are generally associated with patterns of structural defects, it is only when studies of this type are used in combination with more traditional methods that we can achieve an acceptable level of confidence regarding the risk or safety of specific exposures during pregnancy.     

Cystic fibrosis heterozygote screening in 5,161 pregnant women.

A screening program for cystic fibrosis (CF) heterozygotes was conducted in a large HMO prenatal population, to evaluate the level of interest among eligible patients, the effectiveness of prescreening education, attitudes toward the screening process, psychological effects, and utilization of prenatal diagnosis and its outcomes. The heterozygote identification rate and frequency of specific CFTR mutations were also assessed. Identified carriers were offered genetic counseling and testing of male partners. Prenatal diagnosis was offered if both parents were identified as carriers. A total of 5,161 women underwent carrier testing; 947 others completed survey instruments only. The acceptance rate of screening was high (78%), and pretest education by videotape was generally effective. Adverse psychological effects were not reported. Participants generally found screening to be desirable and useful. Screening identified 142 female heterozygotes, 109 couples in which the male partner was not a carrier, and 7 high-risk couples. The incidence of R117H mutations was much higher than expected. The number of identified carriers was much lower in Hispanics than in Caucasians. We conclude that large-scale prenatal screening for CF heterozygotes in the absence of a family history of CF is an acceptable method for identifying couples at risk for affected fetuses. Sufficient pretest education can be accomplished efficiently, test insensitivity is well accepted, adverse psychological events are not observed, and general patient satisfaction is high.     

Carrier screening for Gaucher disease in couples of mixed ethnicity

With the advent of mutational analysis for Gaucher disease, carrier screening has been incorporated into many Jewish genetic disease screening programs. Frequencies and mutations for Gaucher disease in non-Jewish populations are less well established and the detection rate of carriers are lower. Testing is problematic for resolving residual risk in a couple of mixed ethnicity. We report the testing choices made by 20 consecutive couples of mixed ethnicity where the Ashkenazi Jewish partner was identified to be a Gaucher disease gene carrier. Carrier studies of the non-Jewish partner were elected as follows: DNA studies alone, 5 (25%); enzymatic assay, 2 (10%); both, 6 (30%); no carrier studies, 7 (35%). Of the 7 couples not electing carrier studies, one was not in a pregnancy and 6 elected prenatal diagnosis in lieu of parental testing by enzymatic analysis of amniocytes. One couple elected parental carrier studies as well as prenatal diagnosis. All couples electing prenatal Gaucher determination had amniocentesis for other indications as well (4, advanced maternal age; 4, parental anxiety). We conclude that Gaucher screening is feasible for couples of mixed ethnicity if appropriate counseling and testing are offered.     

Psychological Sequelae of Elective Abortion

A mild, short, depressive and guilt ridden period following abortion is quite common, but a severe psychological reaction is rare. The indication for the abortion and the preabortal psychological state of the patient are the two most important factors. Almost all reported instances of postabortion psychoses have occurred in patients who had severe preabortal psychiatric problems. Women undergoing abortion for socioeconomic or psychosocial indications appear to be at minimal risk for long-term negative psychological sequelae. In contrast, women in whom abortion is carried out because of exposure to rubella and the risk of fetal malformation, maternal organic disease or the prenatal diagnosis of a genetically defective fetus are at greater risk and may need supportive psychotherapy.     

Prenatal diagnosis--principles of diagnostic procedures and genetic counseling

The frequency of inherited malformations as well as genetic disorders in newborns account for around 3-5%. These frequency is much higher in early stages of pregnancy, because serious malformations and genetic disorders usually lead to spontaneous abortion. Prenatal diagnosis allowed identification of malformations and/or some genetic syndromes in fetuses during the first trimester of pregnancy. Thereafter, taking into account the severity of the disorders the decision should be taken in regard of subsequent course of the pregnancy taking into account a possibilities of treatment, parent's acceptation of a handicapped child but also, in some cases the possibility of termination of the pregnancy. In prenatal testing, both screening and diagnostic procedures are included. Screening procedures such as first and second trimester biochemical and/or ultrasound screening, first trimester combined ultrasound/biochemical screening and integrated screening should be widely offered to pregnant women. However, interpretation of screening results requires awareness of both sensitivity and predictive value of these procedures. In prenatal diagnosis ultrasound/MRI searching as well as genetic procedures are offered to pregnant women. A variety of approaches for genetic prenatal analyses are now available, including preimplantation diagnosis, chorion villi sampling, amniocentesis, fetal blood sampling as well as promising experimental procedures (e.g. fetal cell and DNA isolation from maternal blood). An incredible progress in genetic methods opened new possibilities for valuable genetic diagnosis. Although karyotyping is widely accepted as golden standard, the discussion is ongoing throughout Europe concerning shifting to new genetic techniques which allow obtaining rapid results in prenatal diagnosis of aneuploidy (e.g. RAPID-FISH, MLPA, quantitative PCR).     

How prenatal diagnosis became acceptable in France

Since the 1960s, prenatal diagnosis techniques have been developed in industrialized countries. There is no therapeutic treatment for most of the diagnosed foetuses and the only solution medicine can offer is abortion; therefore, the techniques might seem controversial. Here, I aim to explore why some prenatal diagnosis and screening techniques are widely used when pregnant women are often ambivalent about them. This article draws on previous sociological work, accounts of health practitioners and a case study of the diffusion of Down's Syndrome prenatal diagnosis in France. It argues that numerous factors, other than the demand of the users, can contribute to speed up the diffusion of a technique.     

Attitudes toward the prenatal diagnosis of cystic fibrosis: factors in decision making among affected families.

The objective of this study was to explore psychosocial factors underlying decisions about use of prenatal diagnosis for cystic fibrosis (CF), among parents of affected children. Anonymous survey questionnaires, supplemented by voluntary interviews, were used at 12 CF centers in six New England states, for a consecutive sample of families of minor children visiting CF centers during a 4-mo period. In all, 227 (71%) of 318 families responded. We hypothesized that attitudes toward utilization would be affected by (a) intentions to have children, (b) knowledge, (c) perception of risk, (d) the health of the child with CF, (e) expectations about the child's future, (f) attitudes toward abortion, (g) insurance, (h) genetic counseling, and (i) sociodemographic factors (including attendance at religious services). Of the 227 couples who responded, 69% were surgically sterile, over 45 years of age, widowed, or divorced, and 31% were at risk. Of 70 at-risk couples, 44% intended to have more children; of these, 77% had had or were considering CF prenatal diagnosis. Most families knew CF could be diagnosed prenatally; 20% would terminate for CF. Among intended prenatal diagnosis users, 44% would carry a fetus with CF to term, 28% would abort, and 28% were undecided. Stepwise logistic regression showed three variables significantly related to intentions to use prenatal diagnosis: (1) respondent's willingness to abort for CF (P less than .02, odds ratio 3.36), (2) respondent's siblings' approval of abortion for CF (P less than .03, odds ratio 2.99), and (3) respondent listed no accomplishments for the child with CF (P less than .09, odds ratio 3.01). The majority of affected families reject selective abortion for CF; many will curtail childbearing rather than use prenatal diagnosis.     

Preimplantation genetic diagnosis and embryo research--human developmental biology in clinical practice.

Research on human preimplantation embryos in vitro is controversial. Yet it has been the cornerstone for the development important clinical assisted conception techniques. Preimplantation genetic diagnosis which has developed out of this assisted reproductive technology for the first time provides a realistic alternative to prenatal diagnosis and abortion for couples who are at substantial risk of conceiving a pregnancy affected by a known genetic disorder. It also provides the first real hope of therapy for couples who have suffered repeated miscarriages due to chromosome translocations. However, the ability to test very early embryos in vitro presents new and unusual ethical challenges for clinicians and developmental biologists.     

Twenty-year outcome analysis of genetic screening programs for Tay-Sachs and beta-thalassemia disease carriers in high schools.

Programs for education, screening, and counseling of senior-high-school students, in populations at high risk for Tay-Sachs and beta-thalassemia diseases, have existed for >20 years in Montreal. Four process and outcome variables are reported here: (i) voluntary participation rates in the high-school cohort; (ii) uptake rates for the screening test; (iii) origin of carrier couples seeking the prenatal diagnosis option in the programs; and (iv) change in incidence of the two diseases. Between 1972 and 1992, we screened 14,844 Ashkenazi-Jewish students, identified 521 HexA-deficient carriers (frequency 1:28), reached 89% of the demographic cohort in the educational component of the program, and achieved 67% voluntary participation in the subsequent screening phase. The corresponding data for the beta-thalassemia program are 25,274 students (mainly of Mediterranean origin) representing 67% of the cohort with 61% voluntary participation in the screening phase (693 carriers; frequency 1:36). From demographic data, we deduce that virtually all the carriers identified in the high-school screening program remembered their status, had their partner tested if they did not already know they were a carrier couple, and took up the options for reproductive counseling/prenatal diagnosis. In Montreal, the current origin of all couples using prenatal diagnosis for Tay-Sachs and beta-thalassemia diseases is the corresponding genetic screening/testing program, whereas, at the beginning of the programs, it was always because there was a history of an affected person in the family. Incidence of the two diseases has fallen by 90%-95% over 20 years; the rare new cases are born (with two exceptions) outside the target communities or to nonscreened couples.     

Prevention of homozygous beta-thalassemia by carrier screening and prenatal diagnosis in Sardinia.

We report here results of a 3-year pilot voluntary screening program coupled with prenatal diagnosis directed to the prospective prevention of homozygous beta-thalassemia (beta-thal) in Sardinia. The screening program took two approaches: outreach community testing and hospital testing on request after a period of sensibilization. The outreach testing was very effective as, taking into account the already known number of couples at risk with an affected proband (20), 74% of the couple at risk expected (61) on the basis of the carrier rate were identified. Less effective was the hospital testing in which half of the couples at risk expected were detected (502 with the 199 without an affected proband). After nondirective genetic counseling, approximately 85% of the couples at risk, which had a pregnancy, with no statistically significant difference between those with and those without a proband, requested prenatal testing. This figure showed a steadily increase from the beginning in 1977 to 1980. All the pregnancies (42), but two carrying homozygous fetuses, were terminated on parental request. A continuous hospital survey of thal-major admissions in the different hospitals of the counties showed a steady decline in the incidence figure at birth from 1976 (1:213) to 1978 (1:290). These results showed that even in a medium-developed, rural, Catholic population screening coupled with prenatal diagnosis can be successful in the control of a fatal, recessively inherited disorder.     

Unusual course of alpha-fetoprotein levels in a case of spina bifida detected by prenatal diagnosis

The authors report the observation of a case of spina bifida detected at the 18th week from a systematic prenatal screening at the C.H.R. in Toulouse, from the assay of alpha foeto-protein on filter paper. The course of total alpha foeto-protein was particularly unique: high levels found at the 18th week with a progressive decrease in concentration until totally normal level was reached during the 28th week. Ecography confirmed the diagnosis of spina bifida. Total alpha foeto-protein concentration was also found at normal level during the 28th week in serum and in amniotic fluid. Therapeutic abortion confirmed the diagnosis of spina bifida. The authors discuss this unique course of alpha foeto-protein levels from the 18th week of development to the 28th week, made possible by this rather valuable observation.     

Periodic health examination, 1996 update: 1. Prenatal screening for and diagnosis of Down syndrome. Canadian Task Force on the Periodic Health Examination.

OBJECTIVE: To make recommendations to physicians providing prenatal care on (1) whether prenatal screening for and diagnosis of Down syndrome (DS) is advisable and (2) alternative screening and diagnosis manoeuvres. OPTIONS: "Triple-marker" screening of maternal serum levels of alpha-fetoprotein, human chorionic gonadotropin and unconjugated estriol; fetal ultrasonographic examination; amniocentesis; and chorionic villus sampling (CVS). OUTCOMES: Accuracy of detection of DS in fetuses, and risks to the mother, including psychologic distress, and to the fetus from the screening and diagnostic interventions. EVIDENCE: A MEDLINE search for relevant articles published from Jan. 1, 1966, to Mar. 31, 1994, with the use of MeSH terms "Down syndrome," "prenatal diagnosis," "screening," "prevention," "amniocentesis," "chorionic villus sampling," "ultrasonography," "anxiety," "depression" and "psychological stress" and a manual search of bibliographies, recent issues of key journals and Current Contents. VALUES: The evidence-based methods and values of the Canadian Task Force on the Periodic Health Examination were used. A high value was placed on providing pregnant women with the opportunity to determine whether they are carrying a fetus with DS and to make choices concerning the termination of the pregnancy. The economic issues involved are complex and were not considered. BENEFITS, HARMS AND COSTS: Triple-marker screening identifies an estimated 58% of fetuses with DS, but it has an estimated rate of true-positive results of 0.1% and of false-positive results of 3.7% (given a risk cut-off of one chance in 190 of DS). These rates vary with maternal age and the risk cut-off chosen. Women with a known risk of having a fetus with DS (e.g., those who have had a previous child with DS) may benefit from a reduction in anxiety after confirmation that their fetus does not have DS. Screening allows women at low risk of having a child with DS to detect fetuses with the syndrome, but may cause psychologic distress if there is a false-positive screening test result. Up to 20% of women with positive results of screening tests may decline to undergo a subsequent amniocentesis. Amniocentesis and CVS are very accurate in diagnosing DS in fetuses and have a very low rate of serious complications for the mother. Amniocentesis is associated with a 1.7% rate of fetal loss when it is performed after 16 weeks'' gestation, whereas the rate among controls is 0.7% (for a difference of 1%, 95% confidence interval 0.3% to 1.5%). CVS entails a greater risk of fetal loss than amniocentesis (odds ratio 1.32, 95% confidence interval 1.11 to 1.57). There is little evidence from controlled trials of significant associations between amniocentesis or CVS and neonatal morbidity or malformations; however, samples have been too small to show differences in rare outcomes. Results from some case-control studies suggest that CVS increases the risk of transverse limb deficiency. Costs were not considered because they are beyond the scope of this review. RECOMMENDATIONS: There is fair evidence to offer triple-marker screening through a comprehensive program to pregnant women under 35 years of age (grade B recommendation). Women given detailed information about serum-marker screening show more satisfaction with the screening than those not given this information. There is fair evidence to offer amniocentesis or CVS to pregnant women 35 years of age and older and to women with a history of a fetus with DS or of a chromosome 21 anomaly (grade B recommendation). Information on the limitations and advantages of each procedure should be offered. Triple-marker screening may be offered as an alternative to CVS or amniocentesis to pregnant women over 35. VALIDATION: Recommendations concerning prenatal diagnosis are similar to those of the US Preventive Services Task Force, the Society of Obstetricians and Gynaecologists of Canada, the Canadian College of Medical Geneticists and the Cochrane Pregnancy and Childbirth Group. No previous specific recommendations concerning triple-maker screening exist. SPONSORS: These guidelines were developed and endorsed by the Canadian Task Force on the Periodic Health Examination, which is funded by Health Canada and the National Health Research and Development Program.