Omphalocele prevalence and co-occurring malformations: a nationwide register-based study of Danish live births in 1997-2021.

Objective: Omphalocele is a congenital abdominal wall defect associated with a high risk of morbidity and mortality, with co-occurring congenital malformations often being the most important prognostic factor. High rates of spontaneous and medical terminations have been reported among pregnancies with omphalocele and co-occurring malformations. Few studies have focused on co-occurring malformations, particularly non-gastrointestinal malformations among live births. This study examined birth prevalence of omphalocele and co-occurring major malformations among a 25-year Danish liveborn cohort.

Methods: This nationwide retrospective prevalence study used data from the Danish National Patient Register and Danish Civil Registration System for infants who were delivered in Denmark during 1997-2021 and included in the Danish neonatal screening biobank. Diagnoses of omphalocele and co-occurring malformations were ascertained and prevalence estimated using Poisson regression.

Results: Among 1,498,685 live births, 147 infants with omphalocele were identified, yielding a combined and stable prevalence (per 10,000 infants) of 0.98 (95% CI 0.83-1.15). Over one-half (53.7%) presented with one or more major malformations, and an additional 17.0% were diagnosed with a syndrome.

Conclusions: Omphalocele birth prevalence in Denmark was stable over a recent 25-year period. The proportion of infants with co-occurring major malformations or diagnosed syndrome has important implications for long-term healthcare demands.