We aimed to assess the frequency of chromosomal abnormalities among infants with congenital heart defects (CHDs) in an analysis of population-based surveillance data. We reviewed data from the Metropolitan Atlanta Congenital Defects Program, a population-based birth-defects surveillance system, to assess the frequency of chromosomal abnormalities among live-born infants and fetal deaths with CHDs delivered from January 1, 1994, to December 31, 2005. Among 4430 infants with CHDs, 547 (12.3%) had a chromosomal abnormality. CHDs most likely to be associated with a chromosomal abnormality were interrupted aortic arch (type B and not otherwise specified; 69.2%), atrioventricular septal defect (67.2%), and double-outlet right ventricle (33.3%). The most common chromosomal abnormalities observed were trisomy 21 (52.8%), trisomy 18 (12.8%), 22q11.2 deletion (12.2%), and trisomy 13 (5.7%). In conclusion, in our study, approximately 1 in 8 infants with a CHD had a chromosomal abnormality. Clinicians should have a low threshold at which to obtain testing for chromosomal abnormalities in infants with CHDs, especially those with certain types of CHDs. Use of new technologies that have become recently available (e.g., chromosomal microarray) may increase the identified contribution of chromosomal abnormalities even further.

Nonsyndromic atrioventricular septal defects (AVSDs) are serious congenital heart defects for which information on prevalence and descriptive characteristics based on large, geographically, and ethnically diverse populations has been limited. To describe the birth prevalence and phenotype of nonsyndromic AVSDs, we used data from the National Birth Defects Prevention Study (NBDPS), a multisite, population-based case-control study aimed at identifying genetic and environmental risk factors for birth defects. For this analysis, infants born during the period 1997-2005 and meeting the NBDPS case definition for AVSDs were included. Infants with an AVSD associated with recognized or strongly suspected chromosomal abnormalities or single-gene disorders (syndromic case infants) were excluded. We identified 302 infants with a nonsyndromic AVSD for a birth prevalence of 0.83/10,000 livebirths. Over 20% of infants with an AVSD had an additional major birth defect, with gastrointestinal, renal or urinary, and central nervous system defects being the most common. A lower prevalence of AVSDs was seen among infants born to Hispanic mothers compared with those born to non-Hispanic White mothers [prevalence ratio = 0.63 (95% confidence interval: 0.46-0.86)]. Understanding the prevalence of nonsyndromic AVSDs, demographic factors associated with their occurrence, and associated defects could help guide clinical care, as well as contribute to a better understanding of pathogenesis.