Objective: Ventricular septal defect (VSD) is currently the most common congenital cardiac malformation in the United States, but little is known about its etiology. The objective of this study was to address the hypothesis that parents' residence in eastern Washington, a region heavily dominated by the agricultural industry, and employment in agriculturally related occupations can influence the presence of a VSD in their offspring.
Design: Population-based case-control study.
Setting: Washington State from January 1, 1987, through December 31, 2003.
Patients: Children aged 0 to 2 years diagnosed as having a VSD (n = 3489), and other infants selected at random as control subjects (n = 13 290).
Main exposures: Parental occupation and county of maternal residence were obtained from the birth certificate. The latter was categorized according to region (east vs west), rural-urban classification, and the proportion of farm and crop land.
Main outcome measures: Diagnosis of VSD within the first 2 years of life.
Results: The risk of VSD was greater for infants whose mothers resided in eastern Washington (odds ratio, 1.30; 95% confidence interval, 1.03-1.65). The risk of VSD with other cardiac malformations (n = 1205) exhibited a stronger geographic association than did isolated VSD (n = 2284). Analyses restricted to eastern Washington did not reveal a clear relationship between the risk of VSD and an increasing proportion of agricultural land in the mother's county of residence. Parental occupation in agriculture was not associated with the presence of VSD.
Conclusion: Although these findings suggest regional variation in Washington State in the occurrence of VSD, the basis for this variation remains to be determined.