Nationwide Danish Register Based Study Showed a Stable Prevalence of Congenital Diaphragmatic Hernias From 1994 to 2021 but a Decrease in Syndromic Cases.

Aim: Congenital diaphragmatic hernia (CDH) is a severe malformation with high morbidity and mortality. This Danish study evaluated the birth prevalence, co-occurring malformations, and temporal trends of CDH over nearly three decades.

Methods: Nationwide data from the Danish Biobank Register were used to identify liveborn infants diagnosed with CDH from 1994 to 2021. They were classified as non-syndromic or syndromic, based on co-occurring structural malformations or genetic or syndromic anomalies. Poisson regression was used to estimate the prevalence, including annual percentage changes.

Results: We found that 272 of the 1 696 357 liveborn infants were diagnosed with CDH, with a stable prevalence of 1.60 per 10 000 live births (95% confidence interval 1.42-1.81). The majority (89.3%) had non-syndromic phenotypes: 79.4% of these had isolated CDH and 20.6% had CDH with co-occurring malformations, predominantly cardiac malformations. Syndromic CDH was observed in 29 (10.7%) infants, and its prevalence declined significantly over the study period (p < 0.03).

Conclusion: Although the prevalence of liveborn Danish CDH births remained stable, there was a shift towards fewer syndromic cases, possibly due to improved prenatal screening and increased terminations. The high proportion of major, co-occurring malformations emphasises the need for continued monitoring to address the healthcare needs of these patients.