Down syndrome and associated atrioventricular septal defects in a nationwide Norwegian cohort: Prevalence, time trends, and outcomes.

Introduction: The prevalence of Down syndrome (DS) is approximately 1 per 1000 births and is influenced by increasing maternal age over the last few decades. DS is strongly associated with congenital heart defects (CHDs), especially atrioventricular septal defect (AVSD). Our objectives were to investigate the prevalence of live-born infants with DS having a severe CHD in the Norwegian population over the last 20 years and compare outcomes in infants with AVSD with and without DS.

Material And Methods: Information on all births from January 1, 2000 to December 31, 2019 was obtained from the Medical Birth Registry of Norway. We also obtained data on all infants with severe CHDs in Norway registered in Oslo University Hospital's Clinical Registry for Congenital Heart Defects during 2000-2019 and accessed individual-level patient data from the electronic hospital records of selected cases. Infants with AVSD and DS were compared to infants with AVSD without chromosomal defects. Crude and adjusted odds ratios (ORs) of infant mortality and need for surgery during the first year of life, with associated 95% confidence intervals (CIs), were estimated by logistic regression.

Results: A total of 1 177 926 infants were live-born in Norway during the study period. Among these, 1456 (0.1%) had DS. The prevalence of infants with DS having a severe CHDs was relatively stable, with a mean of 17 cases per year. The most common CHD associated with DS was AVSD (44.4%). Infants with AVSD and DS were more likely to have cardiac intervention during their first year of life compared to infants with AVSD without chromosomal defects (adjusted OR [aOR]: 2.52; 95% CI 1.27, 4.98). However, we observed no difference in infant mortality during first year of life between the two groups (aOR: 1.08; 95% CI 0.43, 2.70).

Conclusions: The prevalence of live-born infants with severe CHDs and DS has been stable in Norway across 20 years. Infants with AVSD and DS did not have higher risk of mortality during their first year of life compared to infants with AVSD without chromosomal defects, despite a higher risk of operative intervention.