title: Addressing the hidden mortality in CDH: A population-based study.
abstract: BACKGROUND
  Improvements in the clinical management of CDH have led to overall improved reported result from single institutions. However, population-based studies have highlighted a hidden mortality.
  
  
  OBJECTIVE
  To explore the incidence in Sweden and to address the hidden mortality for CDH during a 27-year period in a population-based setting.
  
  
  METHODS
  This is a population based cohort study that includes all patients diagnosed with CDH that were registered in the National Patient Register, the Medical Birth Register, the Register of Congenital Malformations and the Register for Causes of Death between 1987 and 2013. The mortality rates were calculated based on the number deaths divided by the number of live born cases. The hidden mortality was defined as the number of CDH cases that were not born (because of TOP or IUFD), cases of neonatal demise during birth or demise the same day of birth in patients who were in peripheral institutions and who never reached tertiary centers.
  
  
  RESULTS
  In total, 861 CDH patients were born in Sweden between 1987 and 2013, which corresponds to an incidence of 3.0 born CDH per 10,000 live births. When adding the cases of TOP and IUFD, the total incidence of CDH in Sweden was 3.5/10,000 live born. The mortality rate between 1987 and 2013 was 36%: 44% during the first time period 1987-1999 and 27% in the later period 2000-2013. The hidden mortality in the second period was 30%, resulting in a total mortality rate of 45%.
  
  
  CONCLUSIONS
  The incidence of CDH during a 27-year period remained unchanged in the population. However, we observed a decrease in the prevalence because of the increasing numbers of TOP. A significant hidden mortality exists, with overall mortality rate of 45% for CDH in this population.
  
  
  METHODS
  II (cohort).
authors.affiliation: Department of Pediatric Surgery, Karolinska Institutet, Stockholm, Sweden. Electronic address: Carmen.mesas.burgos@ki.se.
authors.forename: Carmen Mesas
authors.initials: CM
authors.lastname: Burgos
authors.affiliation: Department of Pediatric Surgery, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Frenckner
mesh_terms: D000028:Abortion, Induced / Q000706:statistics & numerical data; D015331:Cohort Studies; D005260:Female; D065630:Hernias, Diaphragmatic, Congenital / Q000453:epidemiology / Q000401:mortality*; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D053208:Kaplan-Meier Estimate; D008297:Male; D012042:Registries; D050497:Stillbirth / Q000453:epidemiology; D013548:Sweden / Q000453:epidemiology
keywords: Congenital diaphragmatic hernia (CDH); Hidden mortality; Incidence; Mortality; Population-based study