|Note 1||Includes only trisomy 13, trisomy 18, and Down syndrome confirmed by cytogenetic studies.|
|Note 2||Includes medically indicated pregnancy terminations.|
|Note 3||In the literature rates of serious heart defects vary because of the way atrial septal defect (ASD), ventricular septal defect (VSD) and pulmonic stenosis are counted. Atrial septal defect, ventricular septal defect and pulmonic stenosis were included in the case county only if confirmed by cardiac catheterization, surgery or autopsy. If the atrial septal defect and/or ventricular septal defect are a component of another major heart malformation, the atrial septal defect and/or ventricular septal defect are not counted as a separate defect.|
|Note 4||Includes males only.|
|Note 5||Based on California Birth Defects Monitoring Program research studies and the literature. Children diagnosed through age 8.