Down syndrome is the most common chromosomal disorder which causes physical and intellectual impairment. The most common type is regular type trisomy 21 that is associated with advanced maternal age. Various congenital malformations are frequently seen in individuals with Down syndrome, also congenital heart diseases affect approximately 50% of the patients. In this study, we evaluated the patients diagnosed with Down syndrome (n=439) in our hospital within 15 years to determine the relationship between Down syndrome and advanced maternal age and the frequency of congenital heart diseases. The mean maternal age at birth of the patients included in our study was 32.1 ± 7.0. The incidence of congenital heart diseases was found to be 69.5%, whilst the most common cardiac disease was atrial septal defect. In conclusion, we found that congenital heart disease may be seen in babies with Down syndrome in higher rates than that reported in the literature, additionally Down syndrome may affect babies of mothers much younger than 35 years of age. Anahtar Kelimeler : Down syndrome, trisomy 21, advanced maternal age, congenital heart disease