[Chronic lung disease in a cohort of children born before the 28th gestational week. Incidence and etiological factors].

Introduction: Advances in perinatal care have increased the survival rate of extremely preterm (ETP) infants during the last decades. A key factor has been the ability to provide respiratory support with mechanical ventilation. Mechanical ventilation, however, is associated with pulmonary disease, such as bronchopulmonary dysplasia (BPD). A national prospective study of all EPT infants born in 1994-95 in Denmark found a low incidence of chronic lung disease (CLD), defined as oxygen dependence at 36 weeks postnatal age. In the cohort of surviving infants (n = 195), the incidence of CLD was 15% (95% CI: 11-19). Only 46% of the surviving children had been mechanically ventilated during the neonatal period, and this factor was proposed as an explanation of the low percentage of infants with CLD.

Material And Methods: The present study evaluated CLD in a cohort of EPT infants born in 1998-2001 at Rigshospitalet, the university hospital in Copenhagen. The incidence of CLD was compared to that found in the cohort born in 1994-1995 and the data from the two cohorts were analysed together to investigate changes in CLD.

Results: Although only 39% had been treated with mechanical ventilation in the neonatal period, as many as 37% (95% CI: 31-43) of the surviving children in the study (n = 220) had CLD. Analysing the data from the cohort born in 1994-95 and the cohort born in 1998-2001 together, the increase in CLD could be explained by an improved survival rate and a lower gestational age and birth weight in the 1998-2001 cohort.

Discussion: Our results support the theory that CLD in EPT infants results from insults other than mechanical ventilation.