Prevalence of structural birth defects among infants with Down syndrome, 2013–2017: A US population-based study

Background: Down syndrome is the most common chromosomal disorder at birth and is often accompanied by structural birth defects. Current data on major structural defects in this population are limited. Methods: States and territorial population-based surveillance programs submitted data on identified cases of Down syndrome and identified structural birth defects during 2013–2017. We estimated prevalence by program type and maternal and infant characteristics. Among programs with active case ascertainment, we estimated the prevalence of birth defects by organ system and for specific defects by maternal age (<35, ≥35) and infant sex. Results: We identified 13,376 cases of Down syndrome. Prevalence among all programs was 12.7 per 10,000 live births. Among these children, 75% had at least one reported co-occurring birth defect diagnosis code. Among 6,210 cases identified by active programs, 66% had a cardiovascular defect with septal defects being the most common: atrial (32.5%), ventricular (20.6%), and atrioventricular (17.4%). Defect prevalence differed by infant sex more frequently than by maternal age. For example, atrioventricular septal defects were more common in female children (20.1% vs. 15.1%) while limb deficiencies were more prevalent in male children (0.4% vs. 0.1%). Conclusions: Our study provides updated prevalence estimates for structural defects, including rare defects, among children with Down syndrome using one of the largest and most recent cohorts to date. These data may aid clinical care and surveillance.