Purpose: The population-based National Down Syndrome Project combined epidemiological and molecular methods to study congenital heart defects in Down syndrome. Methods: Between 2000 and 2004, six sites collected DNA, clinical, and epidemiological information on parents and infants. We used logistic regression to examine factors associated with the most common Down syndrome-associated heart defects. Results: Of 1469 eligible infants, major cardiac defects were present in 44%; atrioventricular septal defect (39%), secundum atrial septal defect (42%), ventricular septal defect (43%), and tetralogy of Fallot (6%). Atrioventricular septal defects showed the most significant sex and ethnic differences with twice as many affected females (odds ratio, 1.93; 95% confidence interval, 1.40 -2.67) and, compared with whites, twice as many blacks (odds ratio, 2.06; 95% confidence interval, 1.32-3.21) and half as many Hispanics (odds ratio, 0.48; 95% confidence interval, 0.30 -0.77). No associations were found with origin of the nondisjunction error or with the presence of gastrointestinal defects. Conclusions: Sex and ethnic differences exist for atrioventricular septal defects in Down syndrome.Identification of genetic and environmental risk factors associated with these differences is essential to our understanding of the etiology of congenital heart defects. The National Down Syndrome Project (NDSP) seeks to investigate the etiology and phenotypic consequences of trisomy 21 Down syndrome (DS). 1 Aside from the universal findings of mental retardation and hypotonia, congenital heart defects (CHDs) are arguably the most important clinical sequelae of an extra chromosome 21. In 1998 the Atlanta Down syndrome Project (ADSP), a forerunner of the NDSP, reported that 41% of newborns with DS were born with one or more major heart defects, including atrioventricular septal defect (AVSD), secundum atrial septal defect (ASDII), ventricular septal defect (VSD), and tetralogy of Fallot (TOF). 2 Findings from the ADSP and other recent population-based studies of DS and CHDs 2-5 are summarized in Table 1.With the birth prevalence of major DS-associated CHDs well established by multiple studies using modern diagnostic methods, attention can now be directed toward understanding the etiology of these defects. Not only do infants with DS have a higher rate of CHDs than do infants without DS, but one defect, the AVSD, is particularly characteristic. To understand the etiology of CHDs in DS and of AVSD specifically, both genetic and environmental determinants must be explored. For example, several recent reports have suggested that the distribution of CHDs in DS varies by ethnicity (race/ethnicity), 6 -13 but most population-based studies have not had broad ethnic representation (Table 1). Drawing on our experience with the ADSP, we designed the multicenter NDSP to explore possible CHD risk factors singly and in combination. The NDSP is one of the largest population-based studies of CHDs in DS and the first to assemble clinical, demographic, a...

Mental retardation and hypotonia are found in virtually all Down syndrome (DS) individuals, whereas congenital heart defects (CHDs) are only present in a subset of cases. Although there have been numerous reports of the frequency of CHDs in DS, few of the studies have had complete ascertainment of DS in a defined geographic area. The Atlanta Down Syndrome Project, a population-based study of infants born with trisomy 21, provides such a resource. In the first 6.5 years of the study, 243 trisomy 21 livebirths were identified in the five-county Atlanta area (birth prevalence: 9.6/10,000). Cardiac diagnoses were available on 227 (93%) of the cases and 89% of these evaluations were made by echocardiography, cardiac catheterization, surgery, or autopsy. Of the 227 DS infants, 44% had CHDs including 45% atrioventricular septal defect (with or without other CHDs), 35% ventricular septal defect (with or without other CHDs), 8% isolated secundum atrial septal defect, 7%, isolated persistent patent ductus arteriosus, 4% isolated tetralogy of Fallot, and 1% other. This report is unique in that it contains the largest number of trisomy 21 infants ascertained in a population-based study where modern techniques for diagnosing cardiac abnormalities predominate.

Because the causes of conotruncal cardiac defects are poorly understood, a case-control study was conducted to investigate maternal risk factors for conotruncal cardiac defects. Eligible cases included all infants who were born from 1976 through 1980 to residents of the five county metropolitan Atlanta area and diagnosed with truncus arteriosus, transposition of the great arteries or tetralogy of Fallot. Eligible control infants were a sample of comparable infants without birth defects. Maternal interviews were conducted for 73% (83 of 114) of eligible cases and 72% (1,303 of 1,804) of eligible control infants. The results showed increased risks associated with maternal diabetes (odds ratio 5.6; 90% confidence interval 2.5 to 15.6), maternal stress related to job loss, divorce, separation or death of a close friend or relative (odds ratio 2.4; 90% confidence interval 1.4 to 4.2) and a history of a sibling with a cardiac defect (odds ratio 4.8; 90% confidence interval 2.2 to 10.5). The statistical power of the data was adequate to rule out threefold or greater increases in risk for a wide variety of other exposures, including maternal illnesses other than diabetes, contraceptive use, nonmedicinal drugs (for example, coffee, tea, alcohol, cigarettes, street drugs), employment and education. This population-based study offers no clues that could explain either the high rate of transposition of the great arteries or the temporal trend of an increasing rate of tetralogy of Fallot in Atlanta.

About half of people with trisomy 21 have a congenital heart defect (CHD), whereas the remainder have a structurally normal heart, demonstrating that trisomy 21 is a significant risk factor but is not causal for abnormal heart development. Atrioventricular septal defects (AVSD) are the most commonly occurring heart defects in Down syndrome (DS), and ∼65% of all AVSD is associated with DS. We used a candidate-gene approach among individuals with DS and complete AVSD (cases = 141) and DS with no CHD (controls = 141) to determine whether rare genetic variants in genes involved in atrioventricular valvuloseptal morphogenesis contribute to AVSD in this sensitized population. We found a significant excess (p < 0.0001) of variants predicted to be deleterious in cases compared to controls. At the most stringent level of filtering, we found potentially damaging variants in nearly 20% of cases but fewer than 3% of controls. The variants with the highest probability of being damaging in cases only were found in six genes: COL6A1, COL6A2, CRELD1, FBLN2, FRZB, and GATA5. Several of the case-specific variants were recurrent in unrelated individuals, occurring in 10% of cases studied. No variants with an equal probability of being damaging were found in controls, demonstrating a highly specific association with AVSD. Of note, all of these genes are in the VEGF-A pathway, even though the candidate genes analyzed in this study represented numerous biochemical and developmental pathways, suggesting that rare variants in the VEGF-A pathway might contribute to the genetic underpinnings of AVSD in humans.